Samplers with different type have binding to zero while initializing

[bluekyu]

Panda3D & Render Pipeline

• https://www.panda3d.org/forums/viewtopic.php?f=2&t=19723
• Error messages on AMD graphics tobspr/RenderPipeline#80

OpenGL issues

• https://www.opengl.org/discussion_boards/showthread.php/176366-Samplers-of-different-types-use-the-same-textur
• https://www.opengl.org/discussion_boards/showthread.php/173641-Default-values-for-samplers
• https://www.khronos.org/opengl/wiki/Sampler_(GLSL)#Binding_textures_to_samplers

OpenGL Refs

• https://www.khronos.org/opengl/wiki/Layout_Qualifier_(GLSL)
• https://www.khronos.org/registry/OpenGL-Refpages/gl4/html/glValidateProgram.xhtml

Solution

1. Do glValidateProgram after GL states is ready.
   • However, glValidateProgram cause performance degradation while rendering.
2. Use layout(binding)

[bluekyu]

I guess that Intel OR AMD compiler cannot optimize if IESDatasetTex sampler is used, or not.