add another example w/ image and timing

README.md

@@ -7,7 +7,7 @@ Preparing a 3D model in CSG format (e.g., when using
 [OpenSCAD](http://www.openscad.org/)) for
 printing may take a long time and is often computationally instable.
 
-So `hob3l` wants to replace a workflow 'apply 3D CSG, then slice, then print':
+So Hob3l wants to replace a workflow 'apply 3D CSG, then slice, then print':
 ![3D CSG](img/csg1-old.png)
 
 by a workflow 'slice, then apply 2D CSG, then print':
@@ -59,11 +59,11 @@ your CSG, then do use OpenSCAD's CGAL based rendering.
 
 ## SCAD Input Format
 
-The `hob3l` tool reads a subset of the SCAD format used by OpenSCAD --
+The Hob3l tool reads a subset of the SCAD format used by OpenSCAD --
 I did not want to invent another format.
 
 Please check [the SCAD format documentation](doc/scadformat.md) for a
-definition of the subset of SCAD that is supported by `hob3l`.
+definition of the subset of SCAD that is supported by Hob3l.
 
 ## Algorithmic Improvements
 
@@ -99,7 +99,7 @@ OTOH, the basic workflow is implemented and tested, i.e., the tool can
 read the specified subset of SCAD (e.g. from OpenSCAD's CSG output),
 it can slice the input object, it can apply the 2D boolean operations
 (AKA polygon clipping), and it can triangulate the resulting
-polgygons, and write STL.  Slic3r can read the STL files `hob3l`
+polgygons, and write STL.  Slic3r can read the STL files Hob3l
 produces.
 
 Corner cases in the algorithms have been dealt with (except for
@@ -123,7 +123,7 @@ slic3r, you'll get hundreds of separate layer objects -- which is not
 useful.
 
 Memory management has leaks.  I admit I don't care enough, because
-`hob3l` basically starts, allocates, exits, i.e., it does not run for
+Hob3l basically starts, allocates, exits, i.e., it does not run for
 long, so the memory leaks do not build up.  The goal is to have a
 proper, fast pool based allocation.  This is prepared, but incomplete.
 
@@ -269,7 +269,7 @@ For better package separation, the `install` target is split into
 
 Unfortunately, there is no `install-doc` yet.  FIXME.
 
-The package name `hob3l` can be changed during installation using the
+The package name Hob3l can be changed during installation using the
 `package_name` variable, but this only changes the executable name and
 the library name, but not the include subdirectory, because this would
 not work as the name is explicitly used in the header files.
@@ -278,15 +278,15 @@ not work as the name is explicitly used in the header files.
 
 In general, use `hob3l --help`.
 
-To convert a normal scad file into the subset this `hob3l` can read,
+To convert a normal scad file into the subset this Hob3l can read,
 start by using OpenSCAD to convert to a flat 3D CSG structure with all
 the syntactic sugar removed.  This conversion is fast.
 
 ```
     openscad thing.scad -o thing.csg
 ```
 
-You can now use `hob3l` to slice this directly instead of applying
+You can now use Hob3l to slice this directly instead of applying
 3D CSG:
 
 ```
@@ -301,10 +301,10 @@ This can then be used in your favorite tool for computing print paths.
 
 ### Tweaking Command Line Settings
 
-The underlying technique of `hob3l` is computationally difficult,
+The underlying technique of Hob3l is computationally difficult,
 because it relies on floating point operations.  The goal was
 stability, but it turned out to be really difficult to achieve, so
-`hob3l` might still occasionally fail.  If this happens, the following
+Hob3l might still occasionally fail.  If this happens, the following
 command line options change internal settings that might push the tool
 back on track:
 
@@ -326,15 +326,15 @@ let `eps2` be about the square of `eps`.
 
 ## Speed comparison
 
-Depending on the complexity of the model, `hob3l` may be much faster
+Depending on the complexity of the model, Hob3l may be much faster
 than using OpenSCAD with CGAL rendering.
 
 Some examples:
 
 The x-carriage.scad part of my [Prusa](https://www.prusa3d.com/) i3
 MK3 printer from the Prusa github repository: let's first convert it
 to `.csg`.  This conversion is quickly done with OpenSCAD, and the
-resulting flat SCAD format is what `hob3l` can read:
+resulting flat SCAD format is what Hob3l can read:
 
 ```
     time openscad x-carriage.scad -o x-carriage.csg
@@ -348,7 +348,7 @@ To convert to STL using openscad 3D CSG takes a while:
     0m45.208s
 ```
 
-Doing the same with `hob3l` in 0.2mm layers is about 50 times faster:
+Doing the same with Hob3l in 0.2mm layers is about 50 times faster:
 
 ```
     time hob3l x-carriage.csg -o x-carriage.stl
@@ -357,7 +357,7 @@ Doing the same with `hob3l` in 0.2mm layers is about 50 times faster:
 
 The most complex part of the i3 MK3 printer, the `extruder-body.scad`,
 before it was reimplemented as `step` file, takes 2m42s in openscad to
-convert to STL, while `hob3l` takes 1.24s, again with 0.2mm layers.
+convert to STL, while Hob3l takes 1.24s, again with 0.2mm layers.
 That is 130 times faster.
 
 For one of my own parts `useless-box+body`, which is less complex, but
@@ -376,14 +376,36 @@ This is 85 times faster.  Over half of the time is spent on writing
 the STL file, which is 23MB -- STL is huge.  Loading and converting
 only takes 0.23s.
 
+If you push it, the differences are even more pronounced: the test31b.scad
+example uses `$fn=99` for a few ellipsoids, causing openscad to slow down:
+
+```
+time openscad scad-test/test31b.scad -o test31b.stl
+4m16.270s
+```
+
+In contrast, the different algorithms used by Hob3l do not slow down
+much:
+
+```
+time ./hob3l.exe scad-test/test31b.scad -o test31b.stl
+0m1.011s
+```
+
+This is 250 times faster.  The difference is of course that with
+Hob3l, the result is sliced into layers, as the following image
+demonstrates.
+
+![Hob3l output](img/test31b.jpg)
+
 ## Supported Output Formats
 
-`STL`: The output format of `hob3l` for which it was first developed, is
+`STL`: The output format of Hob3l for which it was first developed, is
 STL.  This way, the input SCAD files can be converted and directly
 used in the slicer for 3D printing.
 
 `PS`: For debugging and documentation, including algorithm
-visualisation, `hob3l` can output in PostScript.  This is how the
+visualisation, Hob3l can output in PostScript.  This is how the
 overview images on this page where generated: by using single-page PS
 output, converted to `PNG` using `GraphicsMagick`.  For debugging,
 mainly multi-page debug PS output was used, which allows easy browsing
@@ -395,8 +417,8 @@ of command line options to customise the output.
 `JS/WEBGL`: For prototyping SCAD files, a web browser can be used as a
 3D model viewer by using the JavaScript/WebGL output format.  The SCAD
 file can be edited in your favourite editor, then for visualisation,
-`hob3l` can generate WebGL data (possibly with an intermediate step to
-let `OpenSCAD` simplify the input file using its .csg output), and a
+Hob3l can generate WebGL data (possibly with an intermediate step to
+let OpenSCAD simplify the input file using its .csg output), and a
 reload in the web browser will show the new model.  This package
 contains auxiliary files to make it immediately usable, e.g. the
 surrounding .html file with the WebGL viewer that loads the generated
@@ -452,6 +474,6 @@ different -- but the result is really the same):
 
 ## Name
 
-The name `hob3l` derives from the German word 'Hobel', which is a
+The name Hob3l derives from the German word 'Hobel', which is a
 'planer' (as in 'wood planer') in English.  The 'e' was turned to `3`
 in recognition of the `slic3r' program.