DAEPhotonsShader

OpenGL Shader Language

GLSL 120

• google:glsl 120 spec
  • http://www.opengl.org/registry/doc/GLSLangSpec.Full.1.20.8.pdf

GLSL 120 Extensions

• http://stackoverflow.com/questions/15107521/opengl-extensions-how-to-use-them-correctly-in-c-and-glsl

GL_EXT_gpu_shader4

• https://www.opengl.org/registry/specs/EXT/gpu_shader4.txt
  • uvec4
  • bitwise operators
  • int/uint attributes

GL_EXT_geometry_shader4

• https://www.opengl.org/registry/specs/EXT/geometry_shader4.txt
• http://www.opengl.org/wiki/Geometry_Shader_Examples
  • vertex and primitive generation in geometry stage between vertex and fragment

glVertexAttribIPointer API hunt

Trying to get integers attributes into shader proving difficult:

delta:OpenGL blyth$ find . -name '*.py' -exec grep -H glVertexAttribIPointer {} \;
./platform/entrypoint31.py:glVertexAttribIPointer
./raw/GL/NV/vertex_program4.py:def glVertexAttribIPointerEXT( index,size,type,stride,pointer ):pass
./raw/GL/VERSION/GL_3_0.py:def glVertexAttribIPointer( index,size,type,stride,pointer ):pass
delta:OpenGL blyth$

• http://developer.download.nvidia.com/opengl/specs/GL_NV_vertex_program4.txt

In [15]: import OpenGL.raw.GL.VERSION.GL_3_0  as g30

In [16]: g30.glVertexAttribIPointer?
Type:       glVertexAttribIPointer
String Form:<OpenGL.platform.baseplatform.glVertexAttribIPointer object at 0x10babc290>
File:       /usr/local/env/chroma_env/lib/python2.7/site-packages/OpenGL/platform/baseplatform.py
Definition: g30.glVertexAttribIPointer(self, *args, **named)
Docstring:  <no docstring>
Call def:   g30.glVertexAttribIPointer(self, *args, **named)

GL_NV_vertex_program4

• trying to use this extension from glsl gives not supported
• http://developer.download.nvidia.com/opengl/specs/GL_NV_vertex_program4.txt

In [11]: import OpenGL.raw.GL.NV.vertex_program4 as nv4

In [12]: nv4.glVertexAttribIPointerEXT
Out[12]: <OpenGL.platform.baseplatform.glVertexAttribIPointerEXT at 0x10bb9fed0>

In [13]: nv4.EXTENSION_NAME
Out[13]: 'GL_NV_vertex_program4'

Fixed Pipeline and Shaders

When using position_name=”position” DAEVertexBuffer does the traditional glVertexPointer setup that furnishes gl_Vertex to the shader.

Legacy way prior to move to generic attributes:

gl_Position = vec4( gl_Vertex.xyz , 1.) ;
//vMomdir = vec4( 100.,100.,100., 1.) ;

Bitwise operations glsl

• http://www.geeks3d.com/20100831/shader-library-noise-and-pseudo-random-number-generator-in-glsl/
• http://stackoverflow.com/questions/2182002/convert-big-endian-to-little-endian-in-c-without-using-provided-func

line strip finnicky

 File "/usr/local/env/chroma_env/lib/python2.7/site-packages/env/geant4/geometry/collada/g4daeview/daephotons.py", line 179, in multidraw
    self.renderer.multidraw(slot=slot, counts=self.counts, firsts=self.firsts, drawcount=self.drawcount )
  File "/usr/local/env/chroma_env/lib/python2.7/site-packages/env/geant4/geometry/collada/g4daeview/daephotonsrenderer.py", line 162, in multidraw
    self.pbuffer.multidraw(mode=gl.GL_LINE_STRIP,  what='', drawcount=qcount, slot=slot, counts=counts, firsts=firsts)
  File "/usr/local/env/chroma_env/lib/python2.7/site-packages/env/geant4/geometry/collada/g4daeview/daevertexbuffer.py", line 500, in multidraw
    gl.glMultiDrawArrays( gl.GL_LINE_STRIP, firsts, counts, drawcount )
  File "/usr/local/env/chroma_env/lib/python2.7/site-packages/OpenGL/platform/baseplatform.py", line 379, in __call__
    return self( *args, **named )
  File "errorchecker.pyx", line 50, in OpenGL_accelerate.errorchecker._ErrorChecker.glCheckError (src/errorchecker.c:854)
  OpenGL.error.GLError: GLError(
    err = 1282,
    description = 'invalid operation',
    baseOperation = glMultiDrawArrays,
    cArguments = (
        GL_LINE_STRIP,
        array([    0,    10,    20, ..., 4162...,
        array([3, 2, 2, ..., 9, 9, 9], dtype=...,
        4165,
    )
)

shaders and integers dont mix in version 120

SHADER['bit_sniffing'] = r"""

// making integers useful inside glsl 120 + GL_EXT_gpu_shader4 is too much effort yo be worthwhile
//  problems
//    #. cannot find symbol glVertexAttribIPointer
//    #. uint type not working so cannot do proper

    uvec4 cf ;
    int nb = 0 ;
    int mb = -1 ;
    for( int n=0 ; n < 32 ; ++n ){
          cf.x = ( 1 << n ) ;
          if (( TEST & cf.x ) != 0){
                nb += 1 ;
                mb = n ;
          }
    }

    if      (mb==29) vColor = vec4( 1.0, 0.0, 0.0, 1.0);
    else if (mb==30) vColor = vec4( 0.0, 1.0, 0.0, 1.0);
    else if (mb==31) vColor = vec4( 0.0, 0.0, 1.0, 1.0);
    else             vColor = vec4( 1.0, 1.0, 1.0, 1.0);

    uvec4 b = uvec4( 0xff, 0xff00, 0xff0000,0xff000000) ;
    uvec4 r = uvec4( TEST >> 24 , TEST >> 8, TEST << 8 , TEST << 24 );
    uvec4 t ;
    t.x = ( r.x & b.x ) | ( r.z & b.z ) | ( r.y & b.y ) | ( r.w & b.w );
"""