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c++openglglslshaderfragment-shader

OpenGL issue with calculating reflection/refraction and uniforms

I'm trying to calculate the reflection/refraction but with I perform a

gl_FragColor = mix(objectColor, environmentColor, 1.0f);

I start getting uniform errors that it can't find my uniform for lightPosition. This doesn't make sense as I'm using that uniform for calculating the diffuse lighting and when I remove the mix function to just gl_FragColor = objectColor; its fine. I'm not sure what I'm doing wrong, if anyone could help out it would be greatly appreciated.

Solution

  • mix(x, y, a) can be expressed as x*(1.0−a) + y*a.

    The last argument of mix is a constant. Hence the expression can be optimized by the compiler.

    gl_FragColor = mix(objectColor, environmentColor, 1.0f);

    is equal to

    gl_FragColor = environmentColor;

    So objectColor is not used and therefore lightPosition is not used either. Hence the uniform lightPosition is not an active program resource.