OpenGL: truncated render textures? (32bit->24bit) (SDK 4.1)
Edit: Changed the title to include further observations (second post).
I am quite happy to have almost successfully integrated the SDK into my own OpenGL engine - except for one problem, which took my at least six hours to narrow it down to the following:
As my engine is a deferred shader, I first render to some geometry buffers, using the RGBA channels of full-resolution textures as efficiently as possible. There are two relevant cases in which I use the alpha channel to store geometry data: Once for the reflectivity and once for the "roughness" (for environment maps and the specular lighting as well as the specular exponent).
However, in a later render step (the actual shading), I only get zero when I try to retrieve the alpha data, while RGB is working fine. So this means, I can see the hole scene, but the shading has no specular lighting or any reflections. When I explicitly replace the alpha channel with "1." in the shader, my lighting works perfectly (except that now every object is excessively shiny).
Also note, that I created my code so, that I can compile it easily without libOVR and in this case, everything works fine (of course, there are some other lines, which change if I do so).
tl;tr
Right now I am suspecting, that the SDK changes an OpenGL render state, which prevents either writing or reading the alpha channel of my framebuffer textures. After checking a lot of glintercept-data, I still cannot find the problem (it's not glColorMask).
Any ideas, what can cause this? Any obscure OpenGL states?
I am quite happy to have almost successfully integrated the SDK into my own OpenGL engine - except for one problem, which took my at least six hours to narrow it down to the following:
As my engine is a deferred shader, I first render to some geometry buffers, using the RGBA channels of full-resolution textures as efficiently as possible. There are two relevant cases in which I use the alpha channel to store geometry data: Once for the reflectivity and once for the "roughness" (for environment maps and the specular lighting as well as the specular exponent).
However, in a later render step (the actual shading), I only get zero when I try to retrieve the alpha data, while RGB is working fine. So this means, I can see the hole scene, but the shading has no specular lighting or any reflections. When I explicitly replace the alpha channel with "1." in the shader, my lighting works perfectly (except that now every object is excessively shiny).
Also note, that I created my code so, that I can compile it easily without libOVR and in this case, everything works fine (of course, there are some other lines, which change if I do so).
tl;tr
Right now I am suspecting, that the SDK changes an OpenGL render state, which prevents either writing or reading the alpha channel of my framebuffer textures. After checking a lot of glintercept-data, I still cannot find the problem (it's not glColorMask).
Any ideas, what can cause this? Any obscure OpenGL states?