Re: [PyOpenGL-Users] Shader Function Problems

[Mike C. F. <mcf...@vr...>]

Ian Mallett wrote:
...
> But strangely, glGetInfoLogARB(...) spits out:
>
>
>
> Fragment shader(s) failed to link,  vertex shader(s) linked. 
> Fragment Shader not supported by HW
>
> Needless to say, it crashes later on glUseProgramObjectARB(...) with an 'invalid operation'.
Yeah, saw the same with my ATI Radeon 3650, I wound up using both 
glGetInfoLog and glGetProgramInfoLog and found that with both I'd 
normally get some description of a failure, but that the shaders would 
pass validation (i.e. the first programmatic indication of the error was 
on the invalid operation error).  For OpenGLContext's shader support I 
wound up doing a try:except around the glUseProgram call and if there's 
a GL error raised I print all of the logs for all of the linked 
components as well as the program's logs.
>   These problems occur when certain functions are called in my program.  Here's a function that causes such an error:
>
>
>   
> float diffuse_coefficient(int lightnum) {
>     vec3 l = normalize(gl_LightSource[lightnum].position.xyz-vVertex);
>     return max(dot(normal,l),0.0);
> }
>
> My ideas:
> vVertex is a varying vec3.  Could this be the problem?
Doesn't look like a problem to me, I seem to recall using varying 
vectors in such ways many times.
> is max(dot(normal,l),0.0) too much for one line?  I saw something 
> about ALU limits.  I don't know if this qualifies. 
I'd be surprised if that went over any limit, I've certainly written 
more complex calculations.

Sorry I don't have more help to offer here.  Might want to check that 
lightnum is the proper value?  Also, stupid question, where'd you get 
"normal" there?  I don't see it in my handy GLSL quickref.  Is it from 
some outer scope (or an attribute/uniform)?

HTH,
Mike

-- 
________________________________________________
  Mike C. Fletcher
  Designer, VR Plumber, Coder
  http://www.vrplumber.com
  http://blog.vrplumber.com