Bgl replacement (and other 3.5 / 4.0 curiosities)

[zeffii]

alternative bgl abstraction.

continuation of #4936

• remove bgl from current node set and modules/utils
• adjust blf.text to handle 3 vs 2 parameters
• implement texture/image loading for texture/buffer using nodes (texture viewers and console node)
  • https://docs.blender.org/api/4.0/gpu.types.html
  • affected nodes ( TextViewer, TVLite, Stethoscope ( nice mode ), Console Node ) , These are not the most
    essential nodes but
    • "nice mode" for stethoscope is pretty cool and if I get that to work then console node will also work
      automatically (they share the same code)
    • Texture Viewer nodes use some Gl code to place the texture in a state to receive data which i'm only tangentially
      familiar with :)
• bug fix front_facing polygon drawing thru
  • lines are not being obscured by polygons.
• polygon offset alternative
  • avoid z-fighting ( proof of concept: at the moment implements a normal shader in custom-shader mode )
  • reimplement custom shader
  • implement shader for flat/facet/smooth

Node	works in < 4.0	works in > 4.0	feature parity	issue
Viewer Draw	yes	yes	no	zfighting lines
Stethoscope MK2	yes	yes	no	advanced drawing to buffer not implemented, no colour highlighting
Matrix View	yes	yes	maybe	plane seems to always draw
Viewer Index	yes	yes	yes	...
Viewer 2D	yes	yes	yes	...
Viewer Draw Curve	yes	yes	yes	...
Viewer Draw Surface	yes	yes	yes	...
Texture Viewer	yes	?	?	?
Texture Viewer Lite	yes	?	?	?
SvWaveformViewer	yes	yes	yes	...
Console Node	yes	?	?	?
Solid Viewer (did not test)	yes	?	?	?
Easing 0..1	yes	yes	yes	...

[zeffii]

with minimal testing I think the branch runs both pre and post B3.5, without spitting errors. However there is a massive degrade in feature set for vdmk4.(and any of the derivatives).. namely:

I like to think I kind of know what i'm doing in GL space, but the gpu.state stuff is not a direct analogue.

[zeffii]

well that seems to work now..

[zeffii]

resolves: #4961
resolves: #4895

[zeffii]

i'm not sure i'll be around to finish this PR, but here is one solution to the removal of the OffsetPolygon feature. We push polygons along their normal, by some small amount, from within a Geometry Shader. I'm not certain that Blender supports Geometry Shaders, however. (fact check? it does!)

https://www.informit.com/articles/article.aspx?p=2120983&seqNum=2

according to this each Geometry Shader call will have a default variable called gl_in which holds (in our case) 3 vectors. Our input primitives are all triangles. .and we can emit new vertices for each of these.

// Calculate two vectors in the plane of the input triangle
vec3 ab = gl_in[1].gl_Position.xyz - gl_in[0].gl_Position.xyz;
vec3 ac = gl_in[2].gl_Position.xyz - gl_in[0].gl_Position.xyz;
vec3 normal = normalize(cross(ab, ac));

and

for (i = 0; i < gl_in.length(); i++)
{
    gl_Position = gl_in[i].gl_Position;
    EmitVertex();
}
//EmitPrimitive();  no need for this if you only emit one primitive 
EndPrimitive();

---

here another intro https://computergraphics.stackexchange.com/questions/5086/how-can-i-offset-shrink-a-triangular-polygon-in-glsl

---

and possibly

mrdoob/three.js#5295 (comment)

where instead of modifying the polygon geometry at "shadertime" , the suggestion seems to be to modify the vectors z coordinate by ~0.0003 from a custom Geometry Shader for Edge geometry.

[zeffii]

https://docs.blender.org/api/current/gpu.types.html#gpu.types.GPUShader

here it does appear we can feed a geometry shader.

Parameters
vertexcode (str) – Vertex shader code.

fragcode – Fragment shader code.

geocode – Geometry shader code.

libcode – Code with functions and presets to be shared between shaders.

defines – Preprocessor directives.

name – Name of shader code, for debugging purposes.

[zeffii]

going down the geometry shader rabbit hole https://stackoverflow.com/questions/14909796/simple-pass-through-geometry-shader-with-normal-and-color

this was useful..

Vertex Shader -> Geometry Shader -> Fragment Shader

https://www.youtube.com/watch?v=C8FK9Xn1gUM

I read somewhere that glsl on Metal doesn't support geometry shaders, not sure if that's true but that does mean a few issues for the codeflow.

[zeffii]

OK!

(this image doesn't do it justice)

[zeffii]

this branch doesn't work in the lastest 4.0 alphas @Durman bpy.types.NodeSocketInterface doesn't exist anymore?

[zeffii]

i guess this technique fails when polygons are facing away from the viewer, therefore it would need to flip the normal in that case.

• but - currently away facing polygons are hidden due to the gpu.state configuration. ( gpu.state.depth_test and ..... . . face_culling_set

fragment_shader, has a built in variable gl_FrontFacing , it's a bool.

    if(gl_FrontFacing)
        FragColor = ... ;
    else
        FragColor = ...  ;

[zeffii]

HARRR!!!

[Durman]

bpy.types.NodeSocketInterface doesn't exist anymore?

I guess it was renamed - https://docs.blender.org/api/4.0/bpy.types.NodeTreeInterfaceSocket.html#bpy.types.NodeTreeInterfaceSocket

But it seems is not the only change, there is new attribute for setting tree interface - https://docs.blender.org/api/4.0/bpy.types.NodeTree.html#bpy.types.NodeTree.interface

[satabol]

Hi @zeffii !
I try this PR in Blender 4.0.1. It is not start, but I found some changes in API:

1. bpy.types.NodeSocketInterface -> bpy.types.NodeTreeInterfaceSocket

Now I can start this PR and it work now:

Your work are very awaited !!! )))

[zeffii]

satabol, OK. i have some time before christmas to spend on sverchok. will try to merge master into this PR and make a version that loads bpy.types.NodeSocketInterface or bpy.types.NodeTreeInterfaceSocket.

i feel OK about merging this soon-ish, as experimental for 4.0 - so people can at least use some of these "GL/BLF" viewers. i'll update the checklist at the top to reflect all that I think is still missing.

[nortikin]

How can we enforse or help with tasks?

[zeffii]

This branch does not yet reach feature parity, but i'm interested to see how it behaves in the wild. If anyone feels like merging this as is, I will be more likely to keep updating the 4.0+ parts (to solve the zfighting in solid/facetted/smooth modes)

[zeffii]

How can we enforse or help with tasks?

my primary goal was to get SV loading regardless of the Blender version, which it does seem to do now. Some graphical glitches (like zfighting edges/polygons) will occur in 4.0+ until a dedicated shader is implemented for 4.0+, but it needs to be executed only when edges and polygons are displayed at the same time)

it's not a big task, I purely haven't sat at a computer for much of the past month.

[nortikin]

In 3.6 there is something backfaced

[zeffii]

Weird. I probably didn't test on 3.6.. This is not good.

[gerroon]

Is this merged?

[nortikin]

when adding node in blender 4.1: works.
when adding node in blender 3.6:

File "D:\users\***\INSTALL\blender-3.6.0-alpha+main.097492b326c7-windows.amd64-release\3.6\scripts\startup\bl_operators\node.py", line 126, in invoke                      
result = self.execute(context)                            
File "C:\Users\***\AppData\Roaming\Blender Foundation\Blender\3.6\scripts\addons\sverchok\ui\nodeview_space_menu.py", line 535, in execute                             
self.deselect_nodes(context)                                  
File "D:\users\***\INSTALL\blender-3.6.0-alpha+main.097492b326c7-windows.amd64-release\3.6\scripts\modules\bpy_types.py", line 816, in __getattribute__                             
return super().__getattribute__(attr)                             
AttributeError: 'SvNodeAddOperator' object has no attribute 'deselect_nodes'


P.S. It works in 4.1 and 3.6 also. It was some kind of exception for unrestarted blender

[nortikin]

4.1:

File "C:\Users\***\AppData\Roaming\Blender Foundation\Blender\4.1\scripts\addons\sverchok\utils\sv_3dview_tools.py", line 97, in sv_execute bpy.ops.view3d.view_center_cursor(ctx) File "D:\users\***\INSTALL\blender-4.1.1-windows-x64\4.1\scripts\modules\bpy\ops.py", line 106, in __call__ C_exec, C_undo = _BPyOpsSubModOp._parse_args(args) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "D:\users\***\INSTALL\blender-4.1.1-windows-x64\4.1\scripts\modules\bpy\ops.py", line 60, in _parse_args raise ValueError("1-2 args execution context is supported") ValueError: 1-2 args execution context is supported

3.6: works

[nortikin]

4.1:
21:23:25.488 [ERROR] sverchok.node_error vertex_utils.py:141 - setting an array element with a sequence. The requested array has an inhomogeneous shape after 1 dimensions. The detected shape was (34,) + inhomogeneous part.

3.6: works