diff --git a/Descent3/Game2DLL.cpp b/Descent3/Game2DLL.cpp
index 3eafc2954..cf080a73e 100644
--- a/Descent3/Game2DLL.cpp
+++ b/Descent3/Game2DLL.cpp
@@ -565,7 +565,7 @@ bool InitGameModule(const char *name, module *mod) {
   std::filesystem::path dll_name;
   std::filesystem::path tmp_dll_name;
   // Make the hog filename
-  lib_name = std::filesystem::path(Base_directory) / "netgames" / name;
+  lib_name = std::filesystem::path("netgames") / name;
   lib_name.replace_extension(".d3m");
   // Make the dll filename
   dll_name = name;
@@ -573,8 +573,7 @@ bool InitGameModule(const char *name, module *mod) {
 
   // Open the hog file
   if (!cf_OpenLibrary(lib_name)) {
-    tmp_dll_name = std::filesystem::path(Base_directory) / "netgames" / name;
-    tmp_dll_name.replace_extension(".d3m");
+    tmp_dll_name = cf_LocatePath(lib_name).u8string().c_str();
     Multi_game_dll_name.clear();
     goto loaddll;
   }
diff --git a/Descent3/Mission.cpp b/Descent3/Mission.cpp
index dcde32a16..00e8cbe2e 100644
--- a/Descent3/Mission.cpp
+++ b/Descent3/Mission.cpp
@@ -921,7 +921,7 @@ bool LoadMission(const char *mssn) {
 
   if (IS_MN3_FILE(mssn)) {
     strcpy(mission, mssn);
-    ddio_MakePath(pathname, D3MissionsDir, mission, NULL);
+    ddio_MakePath(pathname, "missions", mission, NULL);
   } else {
     strcpy(mission, mssn);
     strcpy(pathname, mssn);
@@ -1645,9 +1645,7 @@ void DoMissionMovie(const char *movie) {
   return;
 #endif
   if (movie && *movie) {
-    char mpath[_MAX_PATH];
-    ddio_MakePath(mpath, LocalD3Dir, "movies", movie, NULL);
-    PlayMovie(mpath);
+    PlayMovie(movie);
   }
 }
 
@@ -1835,11 +1833,11 @@ bool mn3_Open(const char *mn3file) {
   char voice_hog[_MAX_PATH*2];
   if ((stricmp(filename, "d3") == 0) || (stricmp(filename, "training") == 0)) {
     // Open audio hog file
-    ddio_MakePath(voice_hog, D3MissionsDir, "d3voice1.hog", nullptr); // Audio for levels 1-4
+    ddio_MakePath(voice_hog, "missions", "d3voice1.hog", nullptr); // Audio for levels 1-4
     Mission_voice_hog_handle = cf_OpenLibrary(voice_hog);
   } else if (stricmp(filename, "d3_2") == 0) {
     // Open audio hog file
-    ddio_MakePath(voice_hog, D3MissionsDir, "d3voice2.hog", nullptr); // Audio for levels 5-17
+    ddio_MakePath(voice_hog, "missions", "d3voice2.hog", nullptr); // Audio for levels 5-17
     Mission_voice_hog_handle = cf_OpenLibrary(voice_hog);
   }
   strcat(filename, ".gam");
@@ -1855,7 +1853,7 @@ bool mn3_GetInfo(const char *mn3file, tMissionInfo *msn) {
   char pathname[_MAX_PATH];
   char filename[PSFILENAME_LEN + 1];
 
-  ddio_MakePath(pathname, D3MissionsDir, mn3file, nullptr);
+  ddio_MakePath(pathname, "missions", mn3file, nullptr);
   handle = cf_OpenLibrary(pathname);
   if (handle == 0) {
     LOG_ERROR << "MISSION: MN3 failed to open.";
diff --git a/Descent3/PilotPicsAPI.cpp b/Descent3/PilotPicsAPI.cpp
index 7d8de7cca..520254d71 100644
--- a/Descent3/PilotPicsAPI.cpp
+++ b/Descent3/PilotPicsAPI.cpp
@@ -132,9 +132,7 @@ bool PPic_InitDatabase(void) {
 
   // attempt to open the hog database
   // --------------------------------
-  char fullpath[_MAX_PATH];
-  ddio_MakePath(fullpath, LocalD3Dir, PILOTPIC_DATABASE_HOG, NULL);
-  PilotPic_database_hog_handle = cf_OpenLibrary(fullpath);
+  PilotPic_database_hog_handle = cf_OpenLibrary(PILOTPIC_DATABASE_HOG);
 
   if (PilotPic_database_hog_handle == 0) {
     // there was an error opening the hog database
diff --git a/Descent3/ambient.cpp b/Descent3/ambient.cpp
index ade9f295f..518ba27dd 100644
--- a/Descent3/ambient.cpp
+++ b/Descent3/ambient.cpp
@@ -293,7 +293,7 @@ void WriteAmbientData() {
   CFILE *ofile;
 
 #ifndef NEWEDITOR
-  ddio_MakePath(filename, Base_directory, "data", "misc", AMBIENT_FILE_NAME, NULL);
+  ddio_MakePath(filename, cf_GetWritableBaseDirectory().u8string().c_str(), "data", "misc", AMBIENT_FILE_NAME, NULL);
 #else
   ddio_MakePath(filename, D3HogDir, "data", "misc", AMBIENT_FILE_NAME, NULL);
 #endif
diff --git a/Descent3/args.cpp b/Descent3/args.cpp
index f3a381932..a7501edd9 100644
--- a/Descent3/args.cpp
+++ b/Descent3/args.cpp
@@ -104,7 +104,7 @@ const char *SkipArgPrefix(const char *arg) {
   return arg;
 }
 
-int FindArg(const char *which) {
+int FindArg(const char *which, int start) {
   if (which == nullptr)
     return 0;
 
@@ -112,14 +112,18 @@ int FindArg(const char *which) {
     return strcasecmp(which, SkipArgPrefix(arg)) == 0;
   };
 
-  for (int i = 1; i <= TotalArgs; i++) {
+  for (int i = start; i <= TotalArgs; i++) {
     if (which_matches(GameArgs[i])) {
       LOG_INFO.printf("FindArg: Found [%s] at argument index (%d).", which, i);
       return i;
     }
   }
 
-  LOG_VERBOSE.printf("FindArg: Did not find [%s] on command line.", which);
+  if (start == 1) {
+    LOG_VERBOSE.printf("FindArg: Did not find [%s] on command line.", which);
+  } else {
+    LOG_VERBOSE.printf("FindArg: Did not find [%s] on command line at index %i or after index %i.", which, start, start);
+  }
   return 0;
 }
 
diff --git a/Descent3/args.h b/Descent3/args.h
index 5794af5ee..1e84b3d4f 100644
--- a/Descent3/args.h
+++ b/Descent3/args.h
@@ -28,7 +28,7 @@ void GatherArgs(const char *str);
 void GatherArgs(char **argv);
 
 // Returns index of argument sought, or 0 if not found
-int FindArg(const char *which);
+int FindArg(const char *which, int start = 1);
 int FindArgChar(const char *which, char singleCharArg);
 
 const char *GetArg(int index);
diff --git a/Descent3/cinematics.cpp b/Descent3/cinematics.cpp
index 06d0b7520..141de09c7 100644
--- a/Descent3/cinematics.cpp
+++ b/Descent3/cinematics.cpp
@@ -45,10 +45,7 @@ bool InitCinematics() {
     return true;
   }
 
-  char path[_MAX_PATH];
-  ddio_MakePath(path, Base_directory, "movies", NULL);
-
-  if (mve_Init(path, Sound_card_name) != MVELIB_NOERROR)
+  if (mve_Init() != MVELIB_NOERROR)
     return false;
 
   mve_SetCallback(CinematicCallback);
diff --git a/Descent3/d3movie.cpp b/Descent3/d3movie.cpp
index 1d627343a..3a123c2ad 100644
--- a/Descent3/d3movie.cpp
+++ b/Descent3/d3movie.cpp
@@ -53,8 +53,7 @@ static bool mve_InitSound();
 static void mve_CloseSound();
 #endif
 
-// sets the directory where movies are stored
-int mve_Init(const char *dir, const char *sndcard) {
+int mve_Init() {
 #ifndef NO_MOVIES
   return MVELIB_NOERROR;
 #else
@@ -72,47 +71,11 @@ void mve_SetCallback(MovieFrameCallback_fp callBack) {
 // used to tell movie library how to render movies.
 void mve_SetRenderProperties(int16_t x, int16_t y, int16_t w, int16_t h, renderer_type type, bool hicolor) {}
 
-#if defined(POSIX)
-// locates the case-sensitive movie file name
-std::filesystem::path mve_FindMovieFileRealName(const std::filesystem::path &movie) {
-  // split into directory and file...
-  std::filesystem::path t_file = movie.filename();
-  std::filesystem::path t_dir = movie.parent_path();
-  std::filesystem::path t_out;
-
-  // found a directory?
-  if (!t_dir.empty()) {
-    // map the bits (or fail)
-    t_out = cf_FindRealFileNameCaseInsensitive(t_file, t_dir);
-    if (t_out.empty())
-      return t_out;
-    // re-assemble
-    return (t_dir / t_out);
-  } else {
-    // just a file, map that
-    t_out = cf_FindRealFileNameCaseInsensitive(t_file);
-    if (t_out.empty())
-      return t_out;
-    // re-assemble
-    return t_out;
-  }
-}
-#endif
-
 // plays a movie using the current screen.
 int mve_PlayMovie(const std::filesystem::path &pMovieName, oeApplication *pApp) {
 #ifndef NO_MOVIES
   // first, find that movie..
-  std::filesystem::path real_name;
-#if defined(POSIX)
-  real_name = mve_FindMovieFileRealName(pMovieName);
-  if (real_name.empty()) {
-    LOG_WARNING.printf("MOVIE: No such file %s", pMovieName.u8string().c_str());
-    return MVELIB_FILE_ERROR;
-  }
-#else
-  real_name = pMovieName;
-#endif
+  std::filesystem::path real_name = cf_LocatePath("movies" / pMovieName);
   // open movie file.
   FILE *hFile = fopen(real_name.u8string().c_str(), "rb");
   if (hFile == nullptr) {
@@ -355,17 +318,7 @@ void CallbackShowFrameNoFlip(unsigned char *buf, unsigned int bufw, unsigned int
 intptr_t mve_SequenceStart(const char *mvename, void *fhandle, oeApplication *app, bool looping) {
 #ifndef NO_MOVIES
   // first, find that movie..
-  std::filesystem::path real_name;
-#if defined(POSIX)
-  real_name = mve_FindMovieFileRealName(mvename);
-  if (real_name.empty()) {
-    LOG_WARNING.printf("MOVIE: No such file %s", mvename);
-    fhandle = nullptr;
-    return 0;
-  }
-#else
-  real_name = mvename;
-#endif
+  std::filesystem::path real_name = cf_LocatePath(std::filesystem::path("movies") / mvename);
   fhandle = fopen(real_name.u8string().c_str(), "rb");
 
   if (fhandle == nullptr) {
diff --git a/Descent3/d3movie.h b/Descent3/d3movie.h
index 558cc3dc4..4cd354435 100644
--- a/Descent3/d3movie.h
+++ b/Descent3/d3movie.h
@@ -33,7 +33,7 @@
 #define MVELIB_PLAYBACK_ERROR (-5)
 #define MVELIB_PLAYBACK_ABORTED (-6)
 
-int mve_Init(const char *dir, const char *sndcard);
+int mve_Init();
 
 // simply plays a movie.
 int mve_PlayMovie(const std::filesystem::path &pMovieName, oeApplication *pApp);
diff --git a/Descent3/demofile.cpp b/Descent3/demofile.cpp
index 2942c208e..7ba81f4bb 100644
--- a/Descent3/demofile.cpp
+++ b/Descent3/demofile.cpp
@@ -359,7 +359,7 @@ void DemoToggleRecording() {
     if (stricmp(szfile + (strlen(szfile) - 4), ".dem") != 0) {
       strcat(szfile, ".dem");
     }
-    Demo_fname = std::filesystem::path(Base_directory) / "demo" / szfile;
+    Demo_fname = cf_GetWritableBaseDirectory() / "demo" / szfile;
     LOG_INFO.printf("Saving demo to file: %s", Demo_fname.u8string().c_str());
     // Try to create the file
     Demo_cfp = cfopen(Demo_fname, "wb");
@@ -1408,7 +1408,7 @@ bool LoadDemoDialog() {
   //	return false;
   // #else
 
-  std::filesystem::path file = std::filesystem::path(Base_directory) / "demo";
+  std::filesystem::path file = cf_GetWritableBaseDirectory() / "demo";
 
   if (DoPathFileDialog(false, file, TXT_VIEWDEMO, {"*.dem"}, PFDF_FILEMUSTEXIST)) {
     Demo_fname = file;
diff --git a/Descent3/descent.cpp b/Descent3/descent.cpp
index 80f223848..46cabed32 100644
--- a/Descent3/descent.cpp
+++ b/Descent3/descent.cpp
@@ -490,7 +490,7 @@ void Descent3() {
         };
 
         for (auto const &intro : intros) {
-          PlayMovie(std::filesystem::path(Base_directory) / "movies" / intro);
+          PlayMovie(intro);
         }
       }
 
diff --git a/Descent3/descent.h b/Descent3/descent.h
index 9ea4f976f..68b0cb5cb 100644
--- a/Descent3/descent.h
+++ b/Descent3/descent.h
@@ -181,9 +181,6 @@ extern bool Descent_overrided_intro;
 // How long the a mission name can be
 #define MSN_NAMELEN 32
 
-// The "root" directory of the D3 file tree
-extern char Base_directory[];
-
 // Variable to preserve current path. TODO: redundant?
 extern std::filesystem::path orig_pwd;
 
diff --git a/Descent3/game.cpp b/Descent3/game.cpp
index 14ad58c86..9a74c0a3d 100644
--- a/Descent3/game.cpp
+++ b/Descent3/game.cpp
@@ -1279,7 +1279,7 @@ void DoScreenshot() {
   count = 1;
   while (!done) {
     snprintf(str, sizeof(str), "Screenshot%.3d.png", count);
-    ddio_MakePath(filename, Base_directory, str, NULL);
+    ddio_MakePath(filename, cf_GetWritableBaseDirectory().u8string().c_str(), str, NULL);
     infile = (CFILE *)cfopen(filename, "rb");
     if (infile == NULL) {
       done = 1;
diff --git a/Descent3/gamesave.cpp b/Descent3/gamesave.cpp
index 7209d2925..bd44e1ed6 100644
--- a/Descent3/gamesave.cpp
+++ b/Descent3/gamesave.cpp
@@ -348,7 +348,7 @@ void QuickSaveGame() {
     i = Quicksave_game_slot;
 
     snprintf(filename, sizeof(filename), "saveg00%d", i);
-    ddio_MakePath(pathname, Base_directory, "savegame", filename, NULL);
+    ddio_MakePath(pathname, cf_GetWritableBaseDirectory().u8string().c_str(), "savegame", filename, NULL);
 
     fp = fopen(pathname, "rb");
     if (fp) {
@@ -391,7 +391,7 @@ void SaveGameDialog() {
 #endif
 
   // setup paths.
-  ddio_MakePath(savegame_dir, Base_directory, "savegame", NULL);
+  ddio_MakePath(savegame_dir, cf_GetWritableBaseDirectory().u8string().c_str(), "savegame", NULL);
   //	ddio_MakePath(pathname, savegame_dir, "*.sav", NULL); -unused
 
   // create savegame directory if it didn't exist before.
@@ -543,7 +543,7 @@ void __cdecl LoadGameDialogCB(newuiTiledWindow *wnd, void *data)
 
     LOG_DEBUG.printf("savegame slot=%d", id - SAVE_HOTSPOT_ID);
 
-    ddio_MakePath(savegame_dir, Base_directory, "savegame", NULL);
+    ddio_MakePath(savegame_dir, cf_GetWritableBaseDirectory().u8string().c_str(), "savegame", NULL);
     snprintf(filename, sizeof(filename), "saveg00%d", (id - SAVE_HOTSPOT_ID));
     ddio_MakePath(pathname, savegame_dir, filename, NULL);
 
@@ -586,7 +586,7 @@ bool LoadGameDialog() {
   }
 
   // setup paths.
-  ddio_MakePath(savegame_dir, Base_directory, "savegame", NULL);
+  ddio_MakePath(savegame_dir, cf_GetWritableBaseDirectory().u8string().c_str(), "savegame", NULL);
   ddio_MakePath(pathname, savegame_dir, "*.sav", NULL);
 
   // create savegame directory if it didn't exist before.
diff --git a/Descent3/gamesequence.cpp b/Descent3/gamesequence.cpp
index d94a799af..fd8a26598 100644
--- a/Descent3/gamesequence.cpp
+++ b/Descent3/gamesequence.cpp
@@ -1295,31 +1295,28 @@ bool GameSequencer() {
 
 // Make sure we have the correct hogfile
 void CheckHogfile() {
-  char hogpath[_MAX_PATH * 2];
+  const char *new_mn3;
   LOG_DEBUG << "Checking to see if we need to open another hog off of disk or CDROM";
 
   if (Current_mission.filename && (stricmp(Current_mission.filename, "d3.mn3") == 0) &&
       (Current_mission.cur_level > 4)) {
-    // close the mission hog file and open d3_2.mn3
-    mn3_Close();
-    ddio_MakePath(hogpath, D3MissionsDir, "d3_2.mn3", nullptr);
-    if (cfexist(hogpath)) {
-      mn3_Open(hogpath);
-      mem_free(Current_mission.filename);
-      Current_mission.filename = mem_strdup("d3_2.mn3");
-    } else {
-      SetFunctionMode(MENU_MODE);
-    }
+    new_mn3 = "d3_2.mn3";
   } else if (Current_mission.filename && (stricmp(Current_mission.filename, "d3_2.mn3") == 0) &&
              (Current_mission.cur_level <= 4)) {
-    // Part 2 of the mission is d3_2.mn3
-    // close the mission hog file and open d3.mn3
+    new_mn3 = "d3.mn3";
+  } else {
+    new_mn3 = NULL;
+  }
+
+  if (new_mn3) {
+    // close the mission hog file and open the new one
     mn3_Close();
-    ddio_MakePath(hogpath, D3MissionsDir, "d3.mn3", nullptr);
-    if (cfexist(hogpath)) {
-      mn3_Open(hogpath);
+    auto relative_path = std::filesystem::path("missions") / new_mn3;
+    auto absolute_path = cf_LocatePath(relative_path);
+    if (std::filesystem::exists(absolute_path)) {
+      mn3_Open(relative_path.u8string().c_str());
       mem_free(Current_mission.filename);
-      Current_mission.filename = mem_strdup("d3.mn3");
+      Current_mission.filename = mem_strdup(new_mn3);
     } else {
       SetFunctionMode(MENU_MODE);
     }
@@ -1628,35 +1625,9 @@ void StartLevel() {
 
 // Loads a level and starts everything up
 bool LoadAndStartCurrentLevel() {
-  char hogpath[_MAX_PATH * 2];
   // This is a bit redundant because we just did it in most cases, but we need to be sure that it always happens,
   // and this code is here for weird systems, like save/load and demo, etc.
-  if (Current_mission.filename && (stricmp(Current_mission.filename, "d3.mn3") == 0) &&
-      (Current_mission.cur_level > 4)) {
-    // close the mission hog file and open d3_2.mn3
-    mn3_Close();
-    ddio_MakePath(hogpath, D3MissionsDir, "d3_2.mn3", nullptr);
-    if (cfexist(hogpath)) {
-      mn3_Open(hogpath);
-      mem_free(Current_mission.filename);
-      Current_mission.filename = mem_strdup("d3_2.mn3");
-    } else {
-      SetFunctionMode(MENU_MODE);
-    }
-  } else if (Current_mission.filename && (stricmp(Current_mission.filename, "d3_2.mn3") == 0) &&
-             (Current_mission.cur_level <= 4)) {
-    // Part 2 of the mission is d3_2.mn3
-    // close the mission hog file and open d3.mn3
-    mn3_Close();
-    ddio_MakePath(hogpath, D3MissionsDir, "d3.mn3", nullptr);
-    if (cfexist(hogpath)) {
-      mn3_Open(hogpath);
-      mem_free(Current_mission.filename);
-      Current_mission.filename = mem_strdup("d3.mn3");
-    } else {
-      SetFunctionMode(MENU_MODE);
-    }
-  }
+  CheckHogfile();
 
   //	load the level. if fails, then bail out
   // ShowProgressScreen (TXT_LOADINGLEVEL);
diff --git a/Descent3/gamespy.cpp b/Descent3/gamespy.cpp
index 29d0f5474..1eaa747cc 100644
--- a/Descent3/gamespy.cpp
+++ b/Descent3/gamespy.cpp
@@ -124,7 +124,7 @@ int gspy_Init() {
   }
 
   // Read the config, resolve the name if needed and setup the server addresses
-  cfgpath = std::filesystem::path(Base_directory) / gspy_cfgfilename;
+  cfgpath = cf_LocatePath(gspy_cfgfilename);
 
   gspy_socket = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
 
diff --git a/Descent3/init.cpp b/Descent3/init.cpp
index 2df70ff07..fcec5fce7 100644
--- a/Descent3/init.cpp
+++ b/Descent3/init.cpp
@@ -1026,9 +1026,6 @@ static bool Graphics_init = false;
 static bool Title_bitmap_init = false;
 uint8_t Use_motion_blur = 0;
 
-// The "root" directory of the D3 file tree
-char Base_directory[_MAX_PATH];
-
 extern int Min_allowed_frametime;
 
 extern bool Render_powerup_sparkles;
@@ -1393,12 +1390,12 @@ void LoadGameSettings() {
 void InitIOSystems(bool editor) {
   ddio_init_info io_info;
 
-  // Set the base directory
+  // Set the writable base directory
   int dirarg = FindArg("-setdir");
   int exedirarg = FindArg("-useexedir");
+  std::filesystem::path writable_base_directory;
   if (dirarg) {
-    strncpy(Base_directory, GameArgs[dirarg + 1], sizeof(Base_directory) - 1);
-    Base_directory[sizeof(Base_directory) - 1] = '\0';
+    writable_base_directory = GameArgs[dirarg + 1];
   } else if (exedirarg) {
     char exec_path[_MAX_PATH];
     memset(exec_path, 0, sizeof(exec_path));
@@ -1407,16 +1404,28 @@ void InitIOSystems(bool editor) {
       Error("Failed to get executable path\n");
     } else {
       std::filesystem::path executablePath(exec_path);
-      std::string baseDirectoryString = executablePath.parent_path().string();
-      strncpy(Base_directory, baseDirectoryString.c_str(), sizeof(Base_directory) - 1);
-      Base_directory[sizeof(Base_directory) - 1] = '\0';
-      LOG_INFO << "Using working directory of " << Base_directory;
+      writable_base_directory = executablePath.parent_path();
+      LOG_INFO << "Using working directory of " << writable_base_directory;
     }
   } else {
-    ddio_GetWorkingDir(Base_directory, sizeof(Base_directory));
+    writable_base_directory = std::filesystem::current_path();
   }
 
-  ddio_SetWorkingDir(Base_directory);
+  ddio_SetWorkingDir(writable_base_directory.u8string().c_str());
+  cf_AddBaseDirectory(writable_base_directory);
+
+  // Set any additional base directories
+  auto additionaldirarg = 0;
+  while (0 != (additionaldirarg = FindArg("-additionaldir", additionaldirarg))) {
+    const auto dir_to_add = GetArg(additionaldirarg + 1);
+    if (dir_to_add == NULL) {
+      LOG_WARNING << "-additionaldir was at the end of the argument list. It should never be at the end of the argument list.";
+      break;
+    } else {
+      cf_AddBaseDirectory(std::filesystem::path(dir_to_add));
+      additionaldirarg += 2;
+    }
+  }
 
   Descent->set_defer_handler(D3DeferHandler);
 
@@ -1469,42 +1478,36 @@ void InitIOSystems(bool editor) {
   // Init hogfiles
   INIT_MESSAGE(("Checking for HOG files."));
   int d3_hid, extra_hid, sys_hid, extra13_hid;
-  char fullname[_MAX_PATH];
+  std::filesystem::path hog_name;
 
 #ifdef DEMO
   // DAJ	d3_hid = cf_OpenLibrary("d3demo.hog");
-  ddio_MakePath(fullname, LocalD3Dir, "d3demo.hog", NULL);
+  hog_name = "d3demo.hog";
 #else
-  ddio_MakePath(fullname, LocalD3Dir, "d3.hog", NULL);
+  hog_name = "d3.hog";
 #endif
-  d3_hid = cf_OpenLibrary(fullname);
+  d3_hid = cf_OpenLibrary(hog_name);
 
   // JC: Steam release uses extra1.hog instead of extra.hog, so try loading it first
   // Open this file if it's present for stuff we might add later
-  ddio_MakePath(fullname, LocalD3Dir, "extra1.hog", NULL);
-  extra_hid = cf_OpenLibrary(fullname);
+  extra_hid = cf_OpenLibrary("extra1.hog");
   if (extra_hid == 0) {
-    ddio_MakePath(fullname, LocalD3Dir, "extra.hog", NULL);
-    extra_hid = cf_OpenLibrary(fullname);
+    extra_hid = cf_OpenLibrary("extra.hog");
   }
 
   // JC: Steam release uses extra.hog instead of merc.hog, so try loading it last (so we don't conflict with the above)
   // Open mercenary hog if it exists
-  ddio_MakePath(fullname, LocalD3Dir, "merc.hog", NULL);
-  merc_hid = cf_OpenLibrary(fullname);
+  merc_hid = cf_OpenLibrary("merc.hog");
   if (merc_hid == 0) {
-    ddio_MakePath(fullname, LocalD3Dir, "extra.hog", NULL);
-    merc_hid = cf_OpenLibrary(fullname);
+    merc_hid = cf_OpenLibrary("extra.hog");
   }
 
   // Open this for extra 1.3 code (Black Pyro, etc)
-  ddio_MakePath(fullname, LocalD3Dir, "extra13.hog", NULL);
-  extra13_hid = cf_OpenLibrary(fullname);
+  extra13_hid = cf_OpenLibrary("extra13.hog");
 
   // last library opened is the first to be searched for dynamic libs, so put
   // this one at the end to find our newly build script libraries first
-  ddio_MakePath(fullname, LocalD3Dir, PRIMARY_HOG, NULL);
-  sys_hid = cf_OpenLibrary(fullname);
+  sys_hid = cf_OpenLibrary(PRIMARY_HOG);
 
   // Check to see if there is a -mission command line option
   // if there is, attempt to open that hog/mn3 so it can override such
@@ -2025,7 +2028,7 @@ void SetupTempDirectory(void) {
     exit(1);
   }
   // restore working dir
-  ddio_SetWorkingDir(Base_directory);
+  ddio_SetWorkingDir(cf_GetWritableBaseDirectory().u8string().c_str());
 }
 
 void DeleteTempFiles() {
diff --git a/Descent3/menu.cpp b/Descent3/menu.cpp
index 1c0a5e2cd..417cd3800 100644
--- a/Descent3/menu.cpp
+++ b/Descent3/menu.cpp
@@ -1061,51 +1061,55 @@ bool ProcessCommandLine() {
 #define TRAINING_MISSION_NAME "Pilot Training"
 
 /**
- * Count singleplayer missions in directory. Mission should have .mn3 extension.
- * @param base_directory where to search missions. Should be a valid directory.
+ * Count singleplayer missions in directories. Mission should have .mn3 extension.
+ * @param missions_directories where to search missions. Should be a list of valid directories.
  * @return count of found missions
  */
-static inline int count_missions(const std::filesystem::path &base_directory) {
+static inline int count_missions(const std::vector<std::filesystem::path> &missions_directories) {
   int c = 0;
 
-  ddio_DoForeachFile(base_directory, std::regex(".*\\.mn3"), [&c](const std::filesystem::path &path) {
-    if (stricmp(path.filename().u8string().c_str(), "d3_2.mn3") == 0)
-      return;
-    LOG_DEBUG.printf("Mission path: %s", path.u8string().c_str());
-    tMissionInfo msninfo{};
-    GetMissionInfo(path.filename().u8string().c_str(), &msninfo);
+  for (const auto &missions_directory : missions_directories) {
+    ddio_DoForeachFile(missions_directory, std::regex(".*\\.mn3"), [&c](const std::filesystem::path &path) {
+      if (stricmp(path.filename().u8string().c_str(), "d3_2.mn3") == 0)
+        return;
+      LOG_DEBUG.printf("Mission path: %s", path.u8string().c_str());
+      tMissionInfo msninfo{};
+      GetMissionInfo(path.filename().u8string().c_str(), &msninfo);
 
-    if (msninfo.name[0] && msninfo.single) {
-      LOG_DEBUG.printf("Name: %s", msninfo.name);
-      c++;
-      if (!(c % 2))
-        DoWaitMessage(true);
-    } else {
-      LOG_DEBUG.printf("Illegal or multiplayer mission: %s", path.u8string().c_str());
-    }
-  });
+      if (msninfo.name[0] && msninfo.single) {
+        LOG_DEBUG.printf("Name: %s", msninfo.name);
+        c++;
+        if (!(c % 2))
+          DoWaitMessage(true);
+      } else {
+        LOG_DEBUG.printf("Illegal or multiplayer mission: %s", path.u8string().c_str());
+      }
+    });
+  }
 
   return c;
 }
 
 static inline int generate_mission_listbox(newuiListBox *lb, int n_maxfiles, char **filelist,
-                                           const std::filesystem::path &base_directory) {
+                                           const std::vector<std::filesystem::path> &missions_directories) {
   int c = 0;
-  ddio_DoForeachFile(
-      base_directory, std::regex(".*\\.mn3"), [&c, &lb, &n_maxfiles, &filelist](const std::filesystem::path &path) {
-        tMissionInfo msninfo{};
-        if (c < n_maxfiles) {
-          if (stricmp(path.filename().u8string().c_str(), "d3_2.mn3") == 0)
-            return;
-          if (GetMissionInfo(path.filename().u8string().c_str(), &msninfo) && msninfo.name[0] && msninfo.single) {
-            filelist[c] = mem_strdup(path.filename().u8string().c_str());
-            lb->AddItem(msninfo.name);
-            c++;
-            if (!(c % 2))
-              DoWaitMessage(true);
+  for (const auto &missions_directory : missions_directories) {
+    ddio_DoForeachFile(
+        missions_directory, std::regex(".*\\.mn3"), [&c, &lb, &n_maxfiles, &filelist](const std::filesystem::path &path) {
+          tMissionInfo msninfo{};
+          if (c < n_maxfiles) {
+            if (stricmp(path.filename().u8string().c_str(), "d3_2.mn3") == 0)
+              return;
+            if (GetMissionInfo(path.filename().u8string().c_str(), &msninfo) && msninfo.name[0] && msninfo.single) {
+              filelist[c] = mem_strdup(path.filename().u8string().c_str());
+              lb->AddItem(msninfo.name);
+              c++;
+              if (!(c % 2))
+                DoWaitMessage(true);
+            }
           }
-        }
-      });
+        });
+  }
 
   return c;
 }
@@ -1182,8 +1186,9 @@ bool MenuNewGame() {
   // add mission names to listbox
   // count valid mission files.
   // add a please wait dialog here.
+  auto missions_directories = cf_LocateMultiplePaths("missions");
   n_missions = 0;
-  n_missions += count_missions(D3MissionsDir);
+  n_missions += count_missions(missions_directories);
   if (n_missions) {
     // allocate extra mission slot because of check below which adds a name to the filelist.
     filelist = (char **)mem_malloc(sizeof(char *) * (n_missions + 1));
@@ -1196,7 +1201,7 @@ bool MenuNewGame() {
     goto missions_fail;
   }
   // generate real listbox now.
-  generate_mission_listbox(msn_lb, n_missions, filelist, D3MissionsDir);
+  generate_mission_listbox(msn_lb, n_missions, filelist, missions_directories);
   // #ifdef RELEASE
   int k;
   for (k = 0; k < n_missions; k++) {
diff --git a/Descent3/mmItem.cpp b/Descent3/mmItem.cpp
index e5a692ef6..34292cdfe 100644
--- a/Descent3/mmItem.cpp
+++ b/Descent3/mmItem.cpp
@@ -330,9 +330,7 @@ void mmInterface::Create() {
     m_movie = NULL;
     static_menu_background = true;
   } else {
-    char filename[_MAX_PATH];
-    ddio_MakePath(filename, Base_directory, "movies", "mainmenu", NULL);
-    m_movie = StartMovie(filename, true);
+    m_movie = StartMovie("mainmenu", true);
 
     if (!m_movie) //[ISB] Didn't find the menu movie?
     {
diff --git a/Descent3/multi.cpp b/Descent3/multi.cpp
index 25b39c870..543d298ed 100644
--- a/Descent3/multi.cpp
+++ b/Descent3/multi.cpp
@@ -8010,23 +8010,23 @@ char *GetFileNameFromPlayerAndID(int16_t playernum, int16_t id) {
     break;
   case NETFILE_ID_SHIP_TEX:
     if (NetPlayers[playernum].ship_logo[0])
-      ddio_MakePath(rval, Base_directory, "custom", "graphics", NetPlayers[playernum].ship_logo, NULL);
+      ddio_MakePath(rval, cf_GetWritableBaseDirectory().u8string().c_str(), "custom", "graphics", NetPlayers[playernum].ship_logo, NULL);
     break;
   case NETFILE_ID_VOICE_TAUNT1:
     if (NetPlayers[playernum].voice_taunt1[0])
-      ddio_MakePath(rval, Base_directory, "custom", "sounds", NetPlayers[playernum].voice_taunt1, NULL);
+      ddio_MakePath(rval, cf_GetWritableBaseDirectory().u8string().c_str(), "custom", "sounds", NetPlayers[playernum].voice_taunt1, NULL);
     break;
   case NETFILE_ID_VOICE_TAUNT2:
     if (NetPlayers[playernum].voice_taunt2[0])
-      ddio_MakePath(rval, Base_directory, "custom", "sounds", NetPlayers[playernum].voice_taunt2, NULL);
+      ddio_MakePath(rval, cf_GetWritableBaseDirectory().u8string().c_str(), "custom", "sounds", NetPlayers[playernum].voice_taunt2, NULL);
     break;
   case NETFILE_ID_VOICE_TAUNT3:
     if (NetPlayers[playernum].voice_taunt3[0])
-      ddio_MakePath(rval, Base_directory, "custom", "sounds", NetPlayers[playernum].voice_taunt3, NULL);
+      ddio_MakePath(rval, cf_GetWritableBaseDirectory().u8string().c_str(), "custom", "sounds", NetPlayers[playernum].voice_taunt3, NULL);
     break;
   case NETFILE_ID_VOICE_TAUNT4:
     if (NetPlayers[playernum].voice_taunt4[0])
-      ddio_MakePath(rval, Base_directory, "custom", "sounds", NetPlayers[playernum].voice_taunt4, NULL);
+      ddio_MakePath(rval, cf_GetWritableBaseDirectory().u8string().c_str(), "custom", "sounds", NetPlayers[playernum].voice_taunt4, NULL);
     break;
   default:
     LOG_FATAL.printf("Unknown id (%d) passed to GetFileNameFromPlayerAndID()", id);
diff --git a/Descent3/multi_dll_mgr.cpp b/Descent3/multi_dll_mgr.cpp
index 1dff4f69e..d7e3d961d 100644
--- a/Descent3/multi_dll_mgr.cpp
+++ b/Descent3/multi_dll_mgr.cpp
@@ -520,6 +520,9 @@ void GetMultiAPI(multi_api *api) {
   api->fp[109] = (int *)GetRankIndex;
   api->fp[110] = (int *)CheckGetD3M;
   api->fp[111] = (int *)ddio_DoForeachFile;
+  api->fp[112] = (int *)cf_LocatePath;
+  api->fp[113] = (int *)cf_LocateMultiplePaths;
+  api->fp[114] = (int *)cf_GetWritableBaseDirectory;
 
   // Variable pointers
   api->vp[0] = (int *)&Player_num;
@@ -527,7 +530,7 @@ void GetMultiAPI(multi_api *api) {
   api->vp[2] = (int *)&Game_is_master_tracker_game;
   api->vp[3] = (int *)&Game_mode;
   api->vp[4] = (int *)NULL; // Current_pilot; no longer a struct
-  api->vp[5] = (int *)Base_directory;
+  api->vp[5] = (int *)NULL; // Base_directory; no longer exists
   api->vp[6] = (int *)&MultiDLLGameStarting;
   api->vp[7] = (int *)MTPilotinfo;
   api->vp[8] = (int *)&Num_network_games_known;
@@ -598,7 +601,7 @@ int LoadMultiDLL(const char *name) {
   if (MultiDLLHandle.handle)
     FreeMultiDLL();
 
-  std::filesystem::path dll_path_name = std::filesystem::path(Base_directory) / "online";
+  std::filesystem::path dll_path_name = cf_GetWritableBaseDirectory() / "online";
   ddio_DoForeachFile(dll_path_name, std::regex(".+\\.tmp"), [](const std::filesystem::path& path, ...) {
     std::error_code ec;
     std::filesystem::remove(path, ec);
@@ -608,7 +611,7 @@ int LoadMultiDLL(const char *name) {
   });
 
   // Make the hog filename
-  lib_name = std::filesystem::path(Base_directory) / "online" / name;
+  lib_name = std::filesystem::path("online") / name;
   lib_name.replace_extension(".d3c");
   // Make the dll filename
   dll_name = name;
@@ -616,7 +619,7 @@ int LoadMultiDLL(const char *name) {
 
   // Open the hog file
   if (!cf_OpenLibrary(lib_name)) {
-    tmp_dll_name = std::filesystem::path(Base_directory) / "online" / name;
+    tmp_dll_name = std::filesystem::path("online") / name;
     tmp_dll_name.replace_extension(".d3c");
     Multi_conn_dll_name.clear();
     goto loaddll;
diff --git a/Descent3/multi_ui.cpp b/Descent3/multi_ui.cpp
index facde1fbe..7ff191151 100644
--- a/Descent3/multi_ui.cpp
+++ b/Descent3/multi_ui.cpp
@@ -442,11 +442,12 @@ int MainMultiplayerMenu() {
 
   std::vector<std::string> dllnames;
 
-  ddio_DoForeachFile(std::filesystem::path(Base_directory) / "online", std::regex(".*\\.d3c"),
-                     [&dllnames](const std::filesystem::path &path) {
-                       std::string filename = path.stem().string();
+  for (const auto &online_directory : cf_LocateMultiplePaths("online")) {
+    ddio_DoForeachFile(online_directory, std::regex(".*\\.d3c"),
+                       [&dllnames](const std::filesystem::path &path) {
+                         std::string filename = path.stem().string();
 
-                       std::replace(filename.begin(), filename.end(), '~', '/');
+                         std::replace(filename.begin(), filename.end(), '~', '/');
 
                        // Place PXO_NAME first in list
                        if (stricmp(filename.c_str(), PXO_NAME) == 0) {
@@ -455,6 +456,7 @@ int MainMultiplayerMenu() {
                          dllnames.push_back(filename);
                        }
                      });
+  }
 
   for (auto const &name : dllnames) {
     lists->AddItem(name.c_str());
@@ -989,7 +991,7 @@ void DoMultiAllowed(void) {
 }
 
 void MultiDoConfigSave() {
-  std::filesystem::path file = std::filesystem::path(Base_directory) / "custom" / "settings";
+  std::filesystem::path file = cf_GetWritableBaseDirectory() / "custom" / "settings";
   if (DoPathFileDialog(true, file, TXT_MULTISAVESET, {"*.mps"}, 0)) {
     file.replace_extension(".mps");
     MultiSaveSettings(file);
@@ -997,7 +999,7 @@ void MultiDoConfigSave() {
 }
 
 void MultiDoConfigLoad() {
-  std::filesystem::path file = std::filesystem::path(Base_directory) / "custom" / "settings";
+  std::filesystem::path file = cf_GetWritableBaseDirectory() / "custom" / "settings";
   if (DoPathFileDialog(false, file, TXT_MULTILOADSET, {"*.mps"}, PFDF_FILEMUSTEXIST))
     MultiLoadSettings(file);
 }
diff --git a/Descent3/pilot.cpp b/Descent3/pilot.cpp
index e2191e8f5..244aa5871 100644
--- a/Descent3/pilot.cpp
+++ b/Descent3/pilot.cpp
@@ -1581,7 +1581,7 @@ bool PltDelete(pilot *Pilot) {
   std::string pfilename = Pilot->get_filename();
   std::error_code ec;
   if (!pfilename.empty()) {
-    return std::filesystem::remove(std::filesystem::path(Base_directory) / pfilename, ec);
+    return std::filesystem::remove(cf_GetWritableBaseDirectory() / pfilename, ec);
   } else {
     Int3(); // this is odd
 
@@ -1595,7 +1595,7 @@ bool PltDelete(pilot *Pilot) {
     PltMakeFNValid(pname);
 
     pfilename = std::string(pname) + PLTEXTENSION;
-    return std::filesystem::remove(std::filesystem::path(Base_directory) / pfilename, ec);
+    return std::filesystem::remove(cf_GetWritableBaseDirectory() / pfilename, ec);
   }
 }
 
@@ -1634,7 +1634,7 @@ void PltReadFile(pilot *Pilot, bool keyconfig, bool missiondata) {
     return;
 
   // open and process file
-  std::filesystem::path filename = std::filesystem::path(Base_directory) / pfilename;
+  std::filesystem::path filename = cf_GetWritableBaseDirectory() / pfilename;
   try {
     file = cfopen(filename, "rb");
     if (!file)
@@ -1677,7 +1677,6 @@ std::vector<std::string> PltGetPilots(std::string ignore_filename, int display_d
   // clear list
   PltClearList();
 
-  std::filesystem::path search = std::filesystem::path(Base_directory);
   std::regex wildcard;
   std::vector<std::string> result;
 
@@ -1699,7 +1698,7 @@ std::vector<std::string> PltGetPilots(std::string ignore_filename, int display_d
       break;
     }
 
-    ddio_DoForeachFile(search, wildcard, [&ignore_filename, &result](const std::filesystem::path &path) {
+    ddio_DoForeachFile(cf_GetWritableBaseDirectory(), wildcard, [&ignore_filename, &result](const std::filesystem::path &path) {
       std::string pilot = path.filename().u8string();
       if (!ignore_filename.empty() && stricmp(ignore_filename.c_str(), pilot.c_str()) == 0) {
         LOG_INFO.printf("Getting Pilots... found %s, but ignoring", pilot.c_str());
@@ -3275,7 +3274,7 @@ void _ReadOldPilotFile(pilot *Pilot, bool keyconfig, bool missiondata) {
   std::string pfilename = Pilot->get_filename();
 
   // open and process file
-  std::filesystem::path filename = std::filesystem::path(Base_directory) / pfilename;
+  std::filesystem::path filename = cf_GetWritableBaseDirectory() / pfilename;
   CFILE *file = cfopen(filename, "rb");
   if (!file)
     return;
diff --git a/Descent3/pilot_class.cpp b/Descent3/pilot_class.cpp
index ad33cdfba..d459fff1a 100644
--- a/Descent3/pilot_class.cpp
+++ b/Descent3/pilot_class.cpp
@@ -415,7 +415,7 @@ int pilot::flush(bool new_file) {
   }
 
   CFILE *file;
-  std::filesystem::path real_filename = std::filesystem::path(Base_directory) / filename;
+  std::filesystem::path real_filename = cf_GetWritableBaseDirectory() / filename;
 
   if (new_file && cfexist(real_filename)) {
     // the file already exists, we can't write out
@@ -497,7 +497,7 @@ int pilot::read(bool skip_config, bool skip_mission_data) {
   }
 
   CFILE *file;
-  std::filesystem::path real_filename = std::filesystem::path(Base_directory) / filename;
+  std::filesystem::path real_filename = cf_GetWritableBaseDirectory() / filename;
 
   if (!cfexist(real_filename)) {
     // the file already exists, we can't write out
diff --git a/Descent3/sdlmain.cpp b/Descent3/sdlmain.cpp
index dca8161e1..3b04e6b8f 100644
--- a/Descent3/sdlmain.cpp
+++ b/Descent3/sdlmain.cpp
@@ -160,7 +160,7 @@ class oeD3LnxDatabase : public oeLnxAppDatabase {
     char *netdir = getenv("D3_DIR");
 
     if (!dir)
-      strcpy(path, Base_directory);
+      strcpy(path, "");
     else
       strcpy(path, dir);
 
diff --git a/cfile/cfile.cpp b/cfile/cfile.cpp
index 275d3366c..27475f2fd 100644
--- a/cfile/cfile.cpp
+++ b/cfile/cfile.cpp
@@ -54,6 +54,16 @@ struct library {
   FILE *file = nullptr; // pointer to file for this lib, if no one using it
 };
 
+/* The "root" directories of the D3 file tree
+ *
+ * Directories that come later in the list override directories that come
+ * earlier in the list. For example, if Base_directories[0] / "d3.hog" exists
+ * and Base_directories[1] / "d3.hog" also exists, then the one in
+ * Base_directories[1] will get used. The one in Base_directories[0] will be
+ * ignored.
+ */
+std::vector<std::filesystem::path> Base_directories = {};
+
 // Map of paths. If value of entry is true, path is only for specific extensions
 std::map<std::filesystem::path, bool> paths;
 
@@ -68,6 +78,133 @@ cfile_error cfe;
 // The message for unexpected end of file
 const char *eof_error = "Unexpected end of file";
 
+/* This function should be called at least once before you use anything else
+ * from this module.
+ */
+void cf_AddBaseDirectory(const std::filesystem::path &base_directory) {
+  if (std::filesystem::exists(base_directory)) {
+    Base_directories.push_back(base_directory);
+  } else {
+    LOG_WARNING << "Ignoring nonexistent base directory: " << base_directory;
+  }
+}
+
+/* After you call this function, you must call cf_AddBaseDirectory() at least
+ * once before you use anything else from this module.
+ */
+void cf_ClearBaseDirectories() {
+  Base_directories.clear();
+}
+
+
+std::filesystem::path cf_LocatePathCaseInsensitiveHelper(const std::filesystem::path &relative_path,
+                                                         const std::filesystem::path &starting_dir) {
+#ifdef WIN32
+  std::filesystem::path result = starting_dir / relative_path;
+  if (std::filesystem::exists(result)) {
+    return result;
+  } else {
+    return {};
+  }
+#else
+  // Dumb check, maybe there already all ok?
+  if (exists((starting_dir / relative_path))) {
+    return starting_dir / relative_path;
+  }
+
+  std::filesystem::path result, search_path, search_file;
+
+  search_path = starting_dir / relative_path.parent_path();
+  search_file = relative_path.filename();
+
+  // If directory does not exist, nothing to search.
+  if (!std::filesystem::is_directory(search_path) || search_file.empty()) {
+    return {};
+  }
+
+
+  // Search component in search_path
+  auto const &it = std::filesystem::directory_iterator(search_path);
+
+  auto found = std::find_if(it, end(it), [&search_file, &search_path, &result](const auto& dir_entry) {
+    return stricmp(dir_entry.path().filename().u8string().c_str(), search_file.u8string().c_str()) == 0;
+  });
+
+  if (found != end(it)) {
+    // Match, append to result
+    result = found->path();
+    search_path = result;
+  } else {
+    // Component not found, mission failed
+    return {};
+  }
+
+  return result;
+#endif
+}
+
+std::vector<std::filesystem::path> cf_LocatePathMultiplePathsHelper(const std::filesystem::path &relative_path,
+                                                                    bool stop_after_first_result) {
+  ASSERT(("realative_path should be a relative path.", relative_path.is_relative()));
+  std::vector<std::filesystem::path> return_value = { };
+  for (auto base_directories_iterator = Base_directories.rbegin();
+       base_directories_iterator != Base_directories.rend();
+       ++base_directories_iterator) {
+    ASSERT(("base_directory should be an absolute path.", base_directories_iterator->is_absolute()));
+    auto to_append = cf_LocatePathCaseInsensitiveHelper(relative_path, *base_directories_iterator);
+    ASSERT(("to_append should be either empty or an absolute path.", to_append.empty() || to_append.is_absolute()));
+    if (std::filesystem::exists(to_append)) {
+      return_value.insert(return_value.begin(), to_append);
+      if (stop_after_first_result) {
+        break;
+      }
+    }
+  }
+  return return_value;
+}
+
+/**
+ * Tries to find a relative path inside of one of the Base_directories.
+ *
+ * @param relative_path A relative path that we’ll hopefully find in
+ *                      one of the Base_directories. You don’t have to get the
+ *                      capitalization of relative_path correct, even on macOS
+ *                      and Linux.
+ *
+ * @return Either an absolute path that’s inside a base directory or an empty
+ *         path if nothing is found.
+ */
+std::filesystem::path cf_LocatePath(const std::filesystem::path &relative_path) {
+  auto return_value_list = cf_LocatePathMultiplePathsHelper(relative_path, true);
+  if (return_value_list.empty()) {
+    return "";
+  } else {
+    return return_value_list.front();
+  }
+}
+
+/**
+ * Tries to find multiple relative paths inside of the Base_directories.
+ *
+ * @param relative_path A relative path that we’ll hopefully find in
+ *                      one or more of the Base_directories. You don’t have to
+ *                      get the capitalization of relative_path correct, even on
+ *                      macOS and Linux.
+ *
+ * @return A list of absolute paths. Each path will be inside one of the
+ *         Base_directories.
+ */
+std::vector<std::filesystem::path> cf_LocateMultiplePaths(const std::filesystem::path &relative_path) {
+  return cf_LocatePathMultiplePathsHelper(relative_path, false);
+}
+
+/* Not all Base_directories are necessarily writable, but this function will
+ * return one that should be writable.
+ */
+std::filesystem::path cf_GetWritableBaseDirectory() {
+  return Base_directories.front();
+}
+
 // Generates a cfile error
 void ThrowCFileError(int type, CFILE *file, const char *msg) {
   cfe.read_write = type;
@@ -82,9 +219,9 @@ static void cf_Close();
 static CFILE *open_file_in_lib(const char *filename);
 
 // Opens a HOG file.  Future calls to cfopen(), etc. will look in this HOG.
-// Parameters:  libname - the path & filename of the HOG file
-// NOTE:	libname must be valid for the entire execution of the program.  Therefore, it should either
-//			be a fully-specified path name, or the current directory must not change.
+// Parameters:  libname - path to the HOG file, relative to one of the Base_directories.
+// NOTE:	libname must be valid for the entire execution of the program.  Therefore, Base_directories
+// 			must not change.
 // Returns: 0 if error, else library handle that can be used to close the library
 int cf_OpenLibrary(const std::filesystem::path &libname) {
   FILE *fp;
@@ -96,25 +233,7 @@ int cf_OpenLibrary(const std::filesystem::path &libname) {
 
   // allocation library structure
   std::shared_ptr<library> lib = std::make_shared<library>();
-
-  // resolve library name
-  std::filesystem::path resolve_dir = libname.parent_path();
-  std::filesystem::path resolve_name = libname;
-
-  if (!resolve_dir.empty()) {
-    resolve_name = libname.filename();
-  }
-
-  std::filesystem::path t_out = cf_FindRealFileNameCaseInsensitive(resolve_name, resolve_dir);
-  if (t_out.empty()) {
-    return 0; // CF_NO_FILE
-  }
-  // re-assemble
-  if (!resolve_dir.empty())
-    lib->name = resolve_dir / t_out;
-  else
-    lib->name = t_out;
-
+  lib->name = cf_LocatePath(libname);
   fp = fopen(lib->name.u8string().c_str(), "rb");
   if (fp == nullptr) {
     return 0; // CF_NO_FILE;
@@ -353,42 +472,6 @@ CFILE *open_file_in_lib(const char *filename) {
   return nullptr;
 }
 
-std::filesystem::path cf_FindRealFileNameCaseInsensitive(const std::filesystem::path &fname,
-                                                         const std::filesystem::path &directory) {
-  // Dumb check, maybe there already all ok?
-  if (exists((directory / fname))) {
-    return fname.filename();
-  }
-
-  std::filesystem::path result, search_path, search_file;
-
-  search_path = directory / fname.parent_path();
-  search_file = fname.filename();
-
-  // If directory does not exist, nothing to search.
-  if (!std::filesystem::is_directory(search_path) || search_file.empty()) {
-    return {};
-  }
-
-  // Search component in search_path
-  auto const &it = std::filesystem::directory_iterator(search_path);
-
-  auto found = std::find_if(it, end(it), [&search_file, &search_path, &result](const auto &dir_entry) {
-    return stricmp(dir_entry.path().filename().u8string().c_str(), search_file.u8string().c_str()) == 0;
-  });
-
-  if (found != end(it)) {
-    // Match, append to result
-    result = found->path();
-    search_path = result;
-  } else {
-    // Component not found, mission failed
-    return {};
-  }
-
-  return result.filename();
-}
-
 // look for the file in the specified directory
 static CFILE *open_file_in_directory(const std::filesystem::path &filename, const char *mode,
                                      const std::filesystem::path &directory);
@@ -403,9 +486,12 @@ CFILE *open_file_in_directory(const std::filesystem::path &filename, const char
   if (std::filesystem::is_directory(directory)) {
     // Make a full path
     using_filename = directory / filename;
-  } else {
-    // no directory specified, so just use filename passed
+  } else if (filename.is_absolute()) {
+    // no directory specified, and filename is an absolute path
     using_filename = filename;
+  } else {
+    // no directory specified, and filename is a relative path
+    using_filename = cf_LocatePath(filename);
   }
 
   // set read or write mode
@@ -416,34 +502,8 @@ CFILE *open_file_in_directory(const std::filesystem::path &filename, const char
   fp = fopen(using_filename.u8string().c_str(), tmode);
 
   if (!fp) {
-#if defined(POSIX)
-    // If we tried to open file for reading, assume there maybe case-sensitive files
-    if (tmode[0] == 'r') {
-      // Try different cases of the filename
-      using_filename = cf_FindRealFileNameCaseInsensitive(filename, directory);
-      if (using_filename.empty()) {
-        // just give up
-        return nullptr;
-      }
-
-      if (std::filesystem::is_directory(directory)) {
-        // Make a full path
-        using_filename = directory / using_filename;
-      }
-
-      fp = fopen(using_filename.u8string().c_str(), tmode);
-      if (!fp) {
-        // no dice
-        return nullptr;
-      }
-    } else {
-      // Error on writing file
-      return nullptr;
-    }
-#else
-    // We on incase-sensitive filesystem, no file means no file.
+    // File not found
     return nullptr;
-#endif
   } else {
     using_filename = filename;
   }
diff --git a/cfile/cfile.h b/cfile/cfile.h
index 7c51d189b..427964281 100644
--- a/cfile/cfile.h
+++ b/cfile/cfile.h
@@ -140,13 +140,64 @@ enum CFileExitStatus {
   CFES_IN_LIBRARY,
 };
 
+/* The "root" directories of the D3 file tree
+ *
+ * Directories that come later in the list override directories that come
+ * earlier in the list. For example, if Base_directories[0] / "d3.hog" exists
+ * and Base_directories[1] / "d3.hog" also exists, then the one in
+ * Base_directories[1] will get used. The one in Base_directories[0] will be
+ * ignored.
+ */
+extern std::vector<std::filesystem::path> Base_directories;
+
+/* This function should be called at least once before you use anything else
+ * from this module.
+ */
+void cf_AddBaseDirectory(const std::filesystem::path &base_directory);
+
+/* After you call this function, you must call cf_AddBaseDirectory() at least
+ * once before you use anything else from this module.
+ */
+void cf_ClearBaseDirectories();
+
+/**
+ * Tries to find a relative path inside of one of the Base_directories.
+ *
+ * @param relative_path A relative path that we’ll hopefully find in
+ *                      one of the Base_directories. You don’t have to get the
+ *                      capitalization of relative_path correct, even on macOS
+ *                      and Linux.
+ *
+ * @return Either an absolute path that’s inside Base_directory or an empty path
+ *         if nothing is found.
+ */
+std::filesystem::path cf_LocatePath(const std::filesystem::path &relative_path);
+
+/**
+ * Tries to find multiple relative paths inside of the Base_directories.
+ *
+ * @param relative_path A relative path that we’ll hopefully find in
+ *                      one or more of the Base_directories. You don’t have to
+ *                      get the capitalization of relative_path correct, even on
+ *                      macOS and Linux.
+ *
+ * @return A list of absolute paths. Each path will be inside one of the
+ *         Base_directories.
+ */
+std::vector<std::filesystem::path> cf_LocateMultiplePaths(const std::filesystem::path &relative_path);
+
+/* Not all Base_directories are necessarily writable, but this function will
+ * return one that should be writable.
+ */
+std::filesystem::path cf_GetWritableBaseDirectory();
+
 // See if a file is in a hog
 bool cf_IsFileInHog(const std::filesystem::path &filename, const std::filesystem::path &hogname);
 
 // Opens a HOG file.  Future calls to cfopen(), etc. will look in this HOG.
-// Parameters:  libname - the path & filename of the HOG file
-// NOTE:	libname must be valid for the entire execution of the program.  Therefore, it should either
-//			be a fully-specified path name, or the current directory must not change.
+// Parameters:  libname - path to the HOG file, relative to one of the Base_directories.
+// NOTE:	libname must be valid for the entire execution of the program.  Therefore, Base_directories
+// 			must not change.
 // Returns: 0 if error, else library handle that can be used to close the library
 int cf_OpenLibrary(const std::filesystem::path &libname);
 
@@ -154,17 +205,6 @@ int cf_OpenLibrary(const std::filesystem::path &libname);
 // Parameters:  handle: the handle returned by cf_OpenLibrary()
 void cf_CloseLibrary(int handle);
 
-/**
- * Returns fixed case file name to actual case on disk for case-sensitive filesystems (Linux).
- * @param fname the fixed case name to map to reality
- * @param directory optional directory to search within (default - current path)
- * @return filename with actual case name or empty path if there no mapping in filesystem
- * @note This function returns only filename without directory part, i.e.
- * cf_FindRealFileNameCaseInsensitive("test/test.txt") will return only "test.txt" on success.
- */
-std::filesystem::path cf_FindRealFileNameCaseInsensitive(const std::filesystem::path &fname,
-                                                         const std::filesystem::path &directory = ".");
-
 /**
  * Add directory path into paths to look in for files. If ext_list is empty,
  * look in this directory for all files. Otherwise, the directory will only
diff --git a/cfile/tests/cfile_tests.cpp b/cfile/tests/cfile_tests.cpp
index 316c65812..c2b046878 100644
--- a/cfile/tests/cfile_tests.cpp
+++ b/cfile/tests/cfile_tests.cpp
@@ -22,7 +22,12 @@
 #include <gtest/gtest.h>
 #include "cfile.h"
 
+void add_cwd_to_base_directories() {
+  cf_AddBaseDirectory(std::filesystem::current_path());
+}
+
 TEST(D3, CFileIO) {
+  add_cwd_to_base_directories();
   int lib_handle = cf_OpenLibrary("TestDir/test.hog");
   CFILE *file_handle = cfopen("lowercase.txt", "rb");
   char buf[5];
@@ -43,6 +48,7 @@ TEST(D3, CFileIO) {
 }
 
 TEST(D3, CFileLibrary) {
+  add_cwd_to_base_directories();
   // First pass - without search path in "TestDir" (i.e. not search actual files in directory)
   // Second pass - with search path (files in directory goes first)
   for (int i = 0; i < 2; i++) {
@@ -70,55 +76,42 @@ TEST(D3, CFileLibrary) {
   EXPECT_EQ(file_handle, nullptr);
 }
 
-TEST(D3, CFileCaseSensitiveSearchNew) {
+TEST(D3, CFileLocatePath) {
   const std::vector<std::filesystem::path> test_paths = {
       std::filesystem::path("TestDir") / "CamelCase.txt",
       std::filesystem::path("TestDir") / "lowercase.txt",
       std::filesystem::path("TestDir") / "UPPERCASE.TXT",
   };
 
-  std::filesystem::path filename_new = cf_FindRealFileNameCaseInsensitive("no-exist-file.txt", "no-exist-dir");
+  std::filesystem::path filename_new = cf_LocatePath(std::filesystem::path("no-exist-dir") / "no-exist-file.txt");
   EXPECT_TRUE(filename_new.empty());
 
-  filename_new = cf_FindRealFileNameCaseInsensitive("no-exist-file.txt");
+  filename_new = cf_LocatePath("no-exist-file.txt");
   EXPECT_TRUE(filename_new.empty());
 
   auto cwd = std::filesystem::current_path();
 
   for (auto const &item : test_paths) {
     auto directory = cwd / item.parent_path();
+    cf_ClearBaseDirectories();
+    cf_AddBaseDirectory(directory);
     std::filesystem::path file = item.filename();
     std::string file_lc = item.filename().u8string();
     std::transform(file_lc.begin(), file_lc.end(), file_lc.begin(), ::tolower);
     std::string file_uc = item.filename().u8string();
     std::transform(file_uc.begin(), file_uc.end(), file_uc.begin(), ::toupper);
 
-    EXPECT_FALSE(cf_FindRealFileNameCaseInsensitive(file_lc, directory).empty());
-    EXPECT_FALSE(cf_FindRealFileNameCaseInsensitive(file_uc, directory).empty());
-
-    EXPECT_FALSE(cf_FindRealFileNameCaseInsensitive(directory / file_lc).empty());
-    EXPECT_FALSE(cf_FindRealFileNameCaseInsensitive(directory / file_uc).empty());
+    EXPECT_FALSE(cf_LocatePath(file_lc).empty());
+    EXPECT_FALSE(cf_LocatePath(file_uc).empty());
 
-    // Now try case-insensitive path with non-existing directory in search.
+    // Now try case-insensitive path with non-existing path.
     // Expected not found on case-sensitive fs.
     file_lc = item.u8string();
     std::transform(file_lc.begin(), file_lc.end(), file_lc.begin(), ::tolower);
     file_uc = item.u8string();
     std::transform(file_uc.begin(), file_uc.end(), file_uc.begin(), ::toupper);
 
-    if (std::filesystem::is_regular_file(file_lc)) {
-      EXPECT_FALSE(cf_FindRealFileNameCaseInsensitive(file_lc, cwd).empty());
-      EXPECT_FALSE(cf_FindRealFileNameCaseInsensitive(file_lc).empty());
-    } else {
-      EXPECT_TRUE(cf_FindRealFileNameCaseInsensitive(file_lc, cwd).empty());
-      EXPECT_TRUE(cf_FindRealFileNameCaseInsensitive(file_lc).empty());
-    }
-    if (std::filesystem::is_regular_file(file_uc)) {
-      EXPECT_FALSE(cf_FindRealFileNameCaseInsensitive(file_uc, cwd).empty());
-      EXPECT_FALSE(cf_FindRealFileNameCaseInsensitive(file_uc).empty());
-    } else {
-      EXPECT_TRUE(cf_FindRealFileNameCaseInsensitive(file_uc, cwd).empty());
-      EXPECT_TRUE(cf_FindRealFileNameCaseInsensitive(file_uc).empty());
-    }
+    EXPECT_TRUE(cf_LocatePath(file_lc).empty());
+    EXPECT_TRUE(cf_LocatePath(file_uc).empty());
   }
 }
diff --git a/ddio/sdlcontroller.cpp b/ddio/sdlcontroller.cpp
index f8101d120..50b70b182 100644
--- a/ddio/sdlcontroller.cpp
+++ b/ddio/sdlcontroller.cpp
@@ -1397,93 +1397,97 @@ int CTLLex(const char *command) {
   return INFFILE_ERROR;
 }
 
-// okay, now search for a '****.ctl' file in the current directory.
+// okay, now search for a '****.ctl' file in the Base_directories
 void sdlgameController::parse_ctl_file(int devnum, const char *ctlname) {
-  // parse each file until we find a name match, no name match, just return
-  ddio_DoForeachFile(
-      Base_directory, std::regex(".*\\.ctl"), [this, &devnum, &ctlname](const std::filesystem::path &path) {
-        InfFile file;
-        bool found_name = false;
-
-        if (file.Open(path.filename(), "[controller settings]", CTLLex)) {
-          // parse each line, setting the appropriate values, etc.
-          while (file.ReadLine()) {
-            int cmd;
-            char operand[128];
-
-            while ((cmd = file.ParseLine(operand, INFFILE_LINELEN)) > INFFILE_ERROR) {
-              // we want to assert that the name command comes before any other to verify
-              // this is the file we really want to change.
-              switch (cmd) {
-              case CTLCMD_NAME:
-                if (strcmp(ctlname, operand) != 0)
-                  goto cancel_file_parse;
-                found_name = true;
-                break;
-
-              case CTLCMD_DEAD: // deadzone
-                if (!found_name)
-                  goto cancel_file_parse;
-                else {
-                  m_ControlList[devnum].deadzone = atof(operand);
-                }
-                break;
-
-              case CTLCMD_AXIS: // allowable axis.
-                                // format of command is "+Z-R"
-                                //	this would add a Z axis to the controller.  -R would remove the Rudder.
-                                // you can do this for X,Y,Z,R,U,V.
-                if (!found_name)
-                  goto cancel_file_parse;
-                else {
-                  int slen = strlen(operand);
-                  for (int i = 0; i <= slen; i += 2) {
-                    int axis_flag;
-                    if ((i + 1) <= slen) {
-                      char axis_cmd = tolower(operand[i + 1]);
-                      if (axis_cmd == 'x')
-                        axis_flag = CTF_X_AXIS;
-                      else if (axis_cmd == 'y')
-                        axis_flag = CTF_Y_AXIS;
-                      else if (axis_cmd == 'z')
-                        axis_flag = CTF_Z_AXIS;
-                      else if (axis_cmd == 'r')
-                        axis_flag = CTF_R_AXIS;
-                      else if (axis_cmd == 'u')
-                        axis_flag = CTF_U_AXIS;
-                      else if (axis_cmd == 'v')
-                        axis_flag = CTF_V_AXIS;
-                      else
-                        axis_flag = 0;
-                      if (operand[i] == '+') {
-                        m_ControlList[devnum].flags |= axis_flag;
-                      } else if (operand[i] == '-') {
-                        m_ControlList[devnum].flags &= (~axis_flag);
+  for (auto base_directories_iterator = Base_directories.rbegin();
+       base_directories_iterator != Base_directories.rend();
+       ++base_directories_iterator) {
+    // parse each file until we find a name match, no name match, just return
+    ddio_DoForeachFile(
+        *base_directories_iterator, std::regex(".*\\.ctl"), [this, &devnum, &ctlname](const std::filesystem::path &path) {
+          InfFile file;
+          bool found_name = false;
+
+          if (file.Open(path.filename(), "[controller settings]", CTLLex)) {
+            // parse each line, setting the appropriate values, etc.
+            while (file.ReadLine()) {
+              int cmd;
+              char operand[128];
+
+              while ((cmd = file.ParseLine(operand, INFFILE_LINELEN)) > INFFILE_ERROR) {
+                // we want to assert that the name command comes before any other to verify
+                // this is the file we really want to change.
+                switch (cmd) {
+                case CTLCMD_NAME:
+                  if (strcmp(ctlname, operand) != 0)
+                    goto cancel_file_parse;
+                  found_name = true;
+                  break;
+
+                case CTLCMD_DEAD: // deadzone
+                  if (!found_name)
+                    goto cancel_file_parse;
+                  else {
+                    m_ControlList[devnum].deadzone = atof(operand);
+                  }
+                  break;
+
+                case CTLCMD_AXIS: // allowable axis.
+                                  // format of command is "+Z-R"
+                                  //	this would add a Z axis to the controller.  -R would remove the Rudder.
+                                  // you can do this for X,Y,Z,R,U,V.
+                  if (!found_name)
+                    goto cancel_file_parse;
+                  else {
+                    int slen = strlen(operand);
+                    for (int i = 0; i <= slen; i += 2) {
+                      int axis_flag;
+                      if ((i + 1) <= slen) {
+                        char axis_cmd = tolower(operand[i + 1]);
+                        if (axis_cmd == 'x')
+                          axis_flag = CTF_X_AXIS;
+                        else if (axis_cmd == 'y')
+                          axis_flag = CTF_Y_AXIS;
+                        else if (axis_cmd == 'z')
+                          axis_flag = CTF_Z_AXIS;
+                        else if (axis_cmd == 'r')
+                          axis_flag = CTF_R_AXIS;
+                        else if (axis_cmd == 'u')
+                          axis_flag = CTF_U_AXIS;
+                        else if (axis_cmd == 'v')
+                          axis_flag = CTF_V_AXIS;
+                        else
+                          axis_flag = 0;
+                        if (operand[i] == '+') {
+                          m_ControlList[devnum].flags |= axis_flag;
+                        } else if (operand[i] == '-') {
+                          m_ControlList[devnum].flags &= (~axis_flag);
+                        } else {
+                          goto cancel_file_parse;
+                        }
                       } else {
-                        goto cancel_file_parse;
+                        break; // this should break out of the axis search but continue with the file
                       }
-                    } else {
-                      break; // this should break out of the axis search but continue with the file
                     }
                   }
+                  break;
+
+                case CTLCMD_SX: // allow modification of global sensitivity modifiers
+                case CTLCMD_SY:
+                case CTLCMD_SZ:
+                case CTLCMD_SR:
+                case CTLCMD_SU:
+                case CTLCMD_SV: {
+                  int idx = (cmd - CTLCMD_SX);
+                  m_ControlList[devnum].sensmod[idx] = atof(operand);
+                  break;
+                }
                 }
-                break;
-
-              case CTLCMD_SX: // allow modification of global sensitivity modifiers
-              case CTLCMD_SY:
-              case CTLCMD_SZ:
-              case CTLCMD_SR:
-              case CTLCMD_SU:
-              case CTLCMD_SV: {
-                int idx = (cmd - CTLCMD_SX);
-                m_ControlList[devnum].sensmod[idx] = atof(operand);
-                break;
-              }
               }
             }
+          cancel_file_parse:
+            file.Close();
           }
-        cancel_file_parse:
-          file.Close();
-        }
-      });
+        });
+  }
 }
diff --git a/editor/MainFrm.cpp b/editor/MainFrm.cpp
index c12cdf38f..009fce25a 100644
--- a/editor/MainFrm.cpp
+++ b/editor/MainFrm.cpp
@@ -1460,7 +1460,7 @@ void InitCScripts() {
   CreateNewMine();
 
   //	Setup include directories for OSIRIS
-  ddio_MakePath(path, Base_directory, "data", "levels", NULL);
+  ddio_MakePath(path, cf_GetWritableBaseDirectory().u8string().c_str(), "data", "levels", NULL);
 }
 
 // Copied from winmain.cpp
diff --git a/editor/editor_lighting.cpp b/editor/editor_lighting.cpp
index 205cab82f..5af799ec2 100644
--- a/editor/editor_lighting.cpp
+++ b/editor/editor_lighting.cpp
@@ -870,7 +870,7 @@ void DoRadiosityForRooms() {
 
   if (save_after_bsp) {
     char filename[_MAX_PATH];
-    ddio_MakePath(filename, Base_directory, "BSPSave.D3L", NULL);
+    ddio_MakePath(filename, cf_GetWritableBaseDirectory().u8string().c_str(), "BSPSave.D3L", NULL);
 
     // Save the level to
     SaveLevel(filename);
@@ -1140,7 +1140,7 @@ void DoRadiosityForRooms() {
   SqueezeLightmaps(0, -1);
 
   char filename[_MAX_PATH + 1];
-  ddio_MakePath(filename, Base_directory, "LightSave.D3L", NULL);
+  ddio_MakePath(filename, cf_GetWritableBaseDirectory().u8string().c_str(), "LightSave.D3L", NULL);
 
   // Save the level to disk
   SaveLevel(filename);
diff --git a/editor/gameeditor.cpp b/editor/gameeditor.cpp
index 20cc0334a..efbb05cad 100644
--- a/editor/gameeditor.cpp
+++ b/editor/gameeditor.cpp
@@ -611,7 +611,7 @@ void GameToEditor(bool set_viewer_from_player) {
   if (Temp_level_saved) {
     char filename[_MAX_PATH];
 
-    ddio_MakePath(filename, Base_directory, "GameSave.D3L", NULL); // make explicit path
+    ddio_MakePath(filename, cf_GetWritableBaseDirectory().u8string().c_str(), "GameSave.D3L", NULL); // make explicit path
     LoadLevel(filename);
     Temp_level_saved = 0;
   }
@@ -744,7 +744,7 @@ void EditorToGame() {
   //	set game working directory
   bool set_size = false;
   ddio_GetWorkingDir(Editor_dir, sizeof(Editor_dir));
-  ddio_SetWorkingDir(Base_directory);
+  ddio_SetWorkingDir(cf_GetWritableBaseDirectory().u8string().c_str());
 
   Osiris_ResetAllTimers();
 
diff --git a/manage/manage.cpp b/manage/manage.cpp
index ff2f60501..b5429d334 100644
--- a/manage/manage.cpp
+++ b/manage/manage.cpp
@@ -672,8 +672,13 @@ int mng_LoadTableFiles(int show_progress) {
 // This is for initting tables on STAND_ALONE, if the network is down, or if
 // the user doesn't want network support
 int mng_InitLocalTables() {
-  // Set the local table directory from the base directory
-  strcpy(LocalD3Dir, Base_directory);
+  // Set the local table directory from the base directory.
+  auto writable_base_directory_string = cf_GetWritableBaseDirectory().u8string();
+  strncpy(LocalD3Dir, writable_base_directory_string.c_str(), sizeof LocalD3Dir);
+  LocalD3Dir[sizeof LocalD3Dir - 1] = '\0';
+  if (strlen(LocalD3Dir) != strlen(writable_base_directory_string.c_str())) {
+    LOG_WARNING << "cf_GetWritableBaseDirectory() is too long to fit in LocalD3Dir, so LocalD3Dir was truncated.";
+  }
   LOG_INFO << "Local dir: " << LocalD3Dir;
 
   // Make the CFILE system first look at our local directories.  If the goods aren't
diff --git a/module/module.cpp b/module/module.cpp
index 6442b854f..121b69077 100644
--- a/module/module.cpp
+++ b/module/module.cpp
@@ -183,8 +183,8 @@ bool mod_LoadModule(module *handle, const std::filesystem::path &imodfilename, i
   handle->handle = dlopen(modfilename.u8string().c_str(), f);
   if (!handle->handle) {
     // ok we couldn't find the given name...try other ways
-    std::filesystem::path parent_path = modfilename.parent_path();
-    std::filesystem::path new_filename = cf_FindRealFileNameCaseInsensitive(modfilename.filename(), parent_path);
+    std::filesystem::path parent_path = modfilename.parent_path().filename();
+    std::filesystem::path new_filename = cf_LocatePath(parent_path / modfilename.filename());
 
     if (new_filename.empty()) {
       LOG_ERROR.printf("Module Load Err: %s", dlerror());
diff --git a/netcon/includes/con_dll.h b/netcon/includes/con_dll.h
index 94c81df85..9cc7cf963 100644
--- a/netcon/includes/con_dll.h
+++ b/netcon/includes/con_dll.h
@@ -701,6 +701,15 @@ typedef void (*ddio_DoForeachFile_fp)(const std::filesystem::path &search_path,
 const std::function<void(std::filesystem::path)> &func);
 ddio_DoForeachFile_fp DLLddio_DoForeachFile;
 
+typedef decltype(&cf_LocatePath) cf_LocatePath_fp;
+cf_LocatePath_fp DLLcf_LocatePath;
+
+typedef decltype(&cf_LocateMultiplePaths) cf_LocateMultiplePaths_fp;
+cf_LocateMultiplePaths_fp DLLcf_LocateMultiplePaths;
+
+typedef decltype(&cf_GetWritableBaseDirectory) cf_GetWritableBaseDirectory_fp;
+cf_GetWritableBaseDirectory_fp DLLcf_GetWritableBaseDirectory;
+
 int DLLUIClass_CurrID = 0xD0;
 
 #define MAX_NET_GAMES 100
@@ -768,7 +777,6 @@ int DLLGame_mode;
 char *DLLTracker_id;
 int *DLLNum_directplay_games;
 netgame_info *DLLNetgame;
-char *DLLLocalD3Dir;
 int *DLLMultiGameStarting;
 netplayer *DLLMNetPlayers;
 int MTWritingPilot, MTReadingPilot;
@@ -998,13 +1006,15 @@ int StartMultiplayerGameMenu() {
 
   DLLListRemoveAll(script_list);
 #if (!(defined(OEM) || defined(DEMO)))
-  DLLddio_DoForeachFile(std::filesystem::path(DLLLocalD3Dir) / "netgames", std::regex(".+\\.d3m"),
-                        [&dll_ui_items](const std::filesystem::path& path){
-                          dll_ui_items.insert_or_assign(
-                              path.stem().u8string(),
-                              DLLCreateNewUITextItem(path.stem().u8string().c_str(), UICOL_LISTBOX_LO, -1)
-                              );
-  } );
+  for (const auto &netgames_directory : DLLcf_LocateMultiplePaths("netgames")) {
+    DLLddio_DoForeachFile(netgames_directory, std::regex(".+\\.d3m"),
+                          [&dll_ui_items](const std::filesystem::path& path){
+                            dll_ui_items.insert_or_assign(
+                                path.stem().u8string(),
+                                DLLCreateNewUITextItem(path.stem().u8string().c_str(), UICOL_LISTBOX_LO, -1)
+                                );
+    } );
+  }
 #else
   dll_ui_items.insert_or_assign("Anarchy", DLLCreateNewUITextItem("Anarchy", UICOL_LISTBOX_LO, -1));
   dll_ui_items.insert_or_assign("Capture The Flag", DLLCreateNewUITextItem("Capture The Flag", UICOL_LISTBOX_LO, -1));
@@ -1017,10 +1027,13 @@ int StartMultiplayerGameMenu() {
 #if (!(defined(OEM) || defined(DEMO)))
   msn_list *mi;
 
-  const std::vector<std::pair<std::filesystem::path, std::regex>> search_paths = {
-    {std::filesystem::path(DLLLocalD3Dir) / "data" / "levels", std::regex(".+\\.msn")},
-    {std::filesystem::path(DLLLocalD3Dir) / "missions", std::regex(".+\\.mn3")}
-  };
+  std::vector<std::pair<std::filesystem::path, std::regex>> search_paths = { };
+  for (const auto &levels_directory : DLLcf_LocateMultiplePaths(std::filesystem::path("data") / "levels")) {
+    search_paths.push_back({levels_directory, std::regex(".+\\.msn")});
+  }
+  for (const auto &missions_directory : DLLcf_LocateMultiplePaths("missions")) {
+    search_paths.push_back({missions_directory, std::regex(".+\\.mn3")});
+  }
 
   for (auto const &i : search_paths) {
     DLLddio_DoForeachFile(i.first, i.second, [&mi, &list_1](const std::filesystem::path &path) {
@@ -1074,7 +1087,7 @@ int StartMultiplayerGameMenu() {
   DLLNetgame->flags = NF_RANDOMIZE_RESPAWN;
   DLLNewUIWindowLoadBackgroundImage(main_wnd, "multimain.ogf");
   DLLNewUIWindowOpen(main_wnd);
-  if (DLLMultiLoadSettings(std::filesystem::path(DLLLocalD3Dir) / "custom" / "settings" / "default.mps")) {
+  if (DLLMultiLoadSettings(DLLcf_GetWritableBaseDirectory() / "custom" / "settings" / "default.mps")) {
     DLLEditSetText(mission_name_edit, DLLNetgame->name);
 #if (!(defined(OEM) || defined(DEMO)))
     p = DLLGetMissionName(DLLNetgame->mission);
diff --git a/netcon/includes/mdllinit.h b/netcon/includes/mdllinit.h
index 2c3895a52..676b250be 100644
--- a/netcon/includes/mdllinit.h
+++ b/netcon/includes/mdllinit.h
@@ -275,6 +275,9 @@ DLLShowNetgameInfo = (ShowNetgameInfo_fp)API.fp[108];
 // API.fp[109]; // Not used
 DLLCheckGetD3M = (CheckGetD3M_fp)API.fp[110];
 DLLddio_DoForeachFile = (ddio_DoForeachFile_fp)API.fp[111];
+DLLcf_LocatePath = (cf_LocatePath_fp)API.fp[112];
+DLLcf_LocateMultiplePaths = (cf_LocateMultiplePaths_fp)API.fp[113];
+DLLcf_GetWritableBaseDirectory = (cf_GetWritableBaseDirectory_fp)API.fp[114];
 
 DLLMPlayers = (player *)API.players;
 DLLNetgame = (netgame_info *)API.netgame;
@@ -286,7 +289,7 @@ DLLTracker_id = (char *)API.vp[1];
 DLLGame_is_master_tracker_game = API.vp[2];
 DLLGame_mode = *API.vp[3];
 // DLLCurrent_pilot = (pilot *)API.vp[4];
-DLLLocalD3Dir = (char *)(pilot *)API.vp[5];
+// DLLLocalD3Dir = (std::filesystem::path *)API.vp[5];
 DLLMultiGameStarting = (int *)API.vp[6];
 DLLMTPilotinfo = (vmt_descent3_struct *)API.vp[7];
 DLLNum_network_games_known = API.vp[8];
diff --git a/netcon/mtclient/mtclient.cpp b/netcon/mtclient/mtclient.cpp
index 39212f85a..bb30d5d7a 100644
--- a/netcon/mtclient/mtclient.cpp
+++ b/netcon/mtclient/mtclient.cpp
@@ -2132,7 +2132,7 @@ void CheckPXOForAnomalies() {
       if (stricmp(DLLMPlayers[i].tracker_id, DLLMPlayers[j].tracker_id) == 0) {
         // Ok, what we have here is multiple users with the same tracker ID.
         // This is bad. It could be user error, but it could be something worse.
-        std::filesystem::path errfilepath = std::filesystem::path(DLLLocalD3Dir) / "pxo.err";
+        std::filesystem::path errfilepath = DLLcf_GetWritableBaseDirectory() / "pxo.err";
         FILE *errfile = fopen(errfilepath.u8string().c_str(), "at");
         if (errfile) {
           fprintf(errfile, "Dup TID: %s & %s / %s\n", DLLMPlayers[j].callsign, DLLMPlayers[i].callsign,
diff --git a/netgames/dmfc/dmfcbase.cpp b/netgames/dmfc/dmfcbase.cpp
index 4e88d8572..dbd9773e0 100644
--- a/netgames/dmfc/dmfcbase.cpp
+++ b/netgames/dmfc/dmfcbase.cpp
@@ -1207,7 +1207,7 @@ void DMFCBase::GameInit(int teams) {
   Remote_Initialize();
 
   // see if we should display Outrage logo at all
-  if (DLLFindArg("-nooutragelogo"))
+  if (DLLFindArg("-nooutragelogo", 1))
     m_bDisplayOutrageLogo = false;
   else
     m_bDisplayOutrageLogo = true;
@@ -4916,7 +4916,7 @@ void DMFCBase::ParseStartupScript(void) {
 
   int autoexec_arg = -1;
 
-  if ((autoexec_arg = DLLFindArg("-autoexec")) != 0) {
+  if ((autoexec_arg = DLLFindArg("-autoexec", 1)) != 0) {
     // a specific autoexec.dmfc file was specified, use that
     strcpy(path, GetGameArg(autoexec_arg + 1));
     mprintf(0, "Override AUTOEXEC.DMFC to %s\n", path);
diff --git a/netgames/dmfc/dmfcfunctions.cpp b/netgames/dmfc/dmfcfunctions.cpp
index e9698ca7c..b9abbb0f1 100644
--- a/netgames/dmfc/dmfcfunctions.cpp
+++ b/netgames/dmfc/dmfcfunctions.cpp
@@ -483,7 +483,7 @@ void (*DLLg3_DrawSpecialLine)(g3Point *p0, g3Point *p1);
 void (*DLLg3_DrawPlanarRotatedBitmap)(vector *pos, vector *norm, angle rot_angle, float width,
                                                    float height, int bm);
 void (*DLLPlayerStopSounds)(int slot);
-int (*DLLFindArg)(const char *which);
+int (*DLLFindArg)(const char *which, int start);
 int (*DLLFireWeaponFromObject)(object *obj, int weapon_num, int gun_num, bool f_force_forward,
                                             bool f_force_target);
 int (*DLLCreateAndFireWeapon)(vector *pos, vector *dir, object *parent, int weapon_num);
diff --git a/netgames/includes/gamedll_header.h b/netgames/includes/gamedll_header.h
index b2758bab1..29c032f2c 100644
--- a/netgames/includes/gamedll_header.h
+++ b/netgames/includes/gamedll_header.h
@@ -1591,7 +1591,7 @@ typedef void (*PlayerStopSounds_fp)(int slot);
 DMFCDLLOUT(PlayerStopSounds_fp DLLPlayerStopSounds;)
 
 // Returns index of argument sought, or 0 if not found
-typedef int (*FindArg_fp)(const char *which);
+typedef decltype(&FindArg) FindArg_fp;
 DMFCDLLOUT(FindArg_fp DLLFindArg;)
 
 // Given an object and a weapon, fires a shot from that object