GLSL gl_FragCoord.z Calculation and Setting gl_FragDepth

Question

So, I\'ve got an imposter (the real geometry is a cube, possibly clipped, and the imposter geometry is a Menger sponge) and I need to calculate its depth.

I can calc

Answer 1

For future reference, the key code is:

float far=gl_DepthRange.far; float near=gl_DepthRange.near;

vec4 eye_space_pos = gl_ModelViewMatrix * /*something*/
vec4 clip_space_pos = gl_ProjectionMatrix * eye_space_pos;

float ndc_depth = clip_space_pos.z / clip_space_pos.w;

float depth = (((far-near) * ndc_depth) + near + far) / 2.0;
gl_FragDepth = depth;