Shader/Defined Uniforms

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Shaders define the following uniforms.

struct gl_DepthRangeParameters
    float near;
    float far;
    float diff;
uniform gl_DepthRangeParameters gl_DepthRange;

uniform int gl_NumSamples; //GLSL 4.20

This struct provides access to the glDepthRange near and far values. The diff​ value is the far​ value minus the near​ value. Do recall that OpenGL makes no requirement that far​ is greater than near​. With regard to multiple Viewports, gl_DepthRange​ only stores the range for viewport 0.

gl_NumSamples​ is the number of samples in the current Framebuffer. If the framebuffer is not multisampled, then this value will be 1.