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/**
* Shader that down-sample depth buffer,
* saving min and max value of each texel in the above mipmaps.
* Adapted from http://rastergrid.com/blog/2010/10/hierarchical-z-map-based-occlusion-culling/
*
* Major simplification has been made since we pad the buffer to always be bigger than input to
* avoid mipmapping misalignment.
*/
#ifdef LAYERED
uniform sampler2DArray depthBuffer;
uniform int depthLayer;
#else
uniform sampler2D depthBuffer;
#endif
#ifndef COPY_DEPTH
uniform vec2 texelSize;
#endif
#ifdef LAYERED
# define sampleLowerMip(t) texture(depthBuffer, vec3(t, depthLayer)).r
# define gatherLowerMip(t) textureGather(depthBuffer, vec3(t, depthLayer))
#else
# define sampleLowerMip(t) texture(depthBuffer, t).r
# define gatherLowerMip(t) textureGather(depthBuffer, t)
#endif
#ifdef MIN_PASS
# define minmax2(a, b) min(a, b)
# define minmax3(a, b, c) min(min(a, b), c)
# define minmax4(a, b, c, d) min(min(min(a, b), c), d)
#else /* MAX_PASS */
# define minmax2(a, b) max(a, b)
# define minmax3(a, b, c) max(max(a, b), c)
# define minmax4(a, b, c, d) max(max(max(a, b), c), d)
#endif
/* On some AMD card / driver combination, it is needed otherwise,
* the shader does not write anything. */
#if defined(GPU_INTEL) || defined(GPU_ATI)
out vec4 fragColor;
#endif
void main()
{
vec2 texel = gl_FragCoord.xy;
#ifdef COPY_DEPTH
vec2 uv = texel / vec2(textureSize(depthBuffer, 0).xy);
float val = sampleLowerMip(uv);
#else
/* NOTE(@fclem): textureSize() does not work the same on all implementations
* when changing the min and max texture levels. Use uniform instead (see T87801). */
vec2 uv = texel * 2.0 * texelSize;
vec4 samp;
# ifdef GPU_ARB_texture_gather
samp = gatherLowerMip(uv);
# else
samp.x = sampleLowerMip(uv + vec2(-0.5, -0.5) * texelSize);
samp.y = sampleLowerMip(uv + vec2(-0.5, 0.5) * texelSize);
samp.z = sampleLowerMip(uv + vec2(0.5, -0.5) * texelSize);
samp.w = sampleLowerMip(uv + vec2(0.5, 0.5) * texelSize);
# endif
float val = minmax4(samp.x, samp.y, samp.z, samp.w);
#endif
#if defined(GPU_INTEL) || defined(GPU_ATI)
/* Use color format instead of 24bit depth texture */
fragColor = vec4(val);
#endif
gl_FragDepth = val;
}
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