65 lines
1.8 KiB
GLSL
65 lines
1.8 KiB
GLSL
/**
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* Shader that downsample depth buffer,
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* saving min and max value of each texel in the above mipmaps.
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* Adapted from http://rastergrid.com/blog/2010/10/hierarchical-z-map-based-occlusion-culling/
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**/
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#ifdef LAYERED
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uniform sampler2DArray depthBuffer;
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uniform int depthLayer;
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#else
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uniform sampler2D depthBuffer;
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#endif
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#ifdef LAYERED
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#define sampleLowerMip(t) texelFetch(depthBuffer, ivec3(t, depthLayer), 0).r
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#else
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#define sampleLowerMip(t) texelFetch(depthBuffer, t, 0).r
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#endif
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#ifdef MIN_PASS
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#define minmax(a, b) min(a, b)
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#else /* MAX_PASS */
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#define minmax(a, b) max(a, b)
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#endif
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void main()
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{
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ivec2 texelPos = ivec2(gl_FragCoord.xy);
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ivec2 mipsize = textureSize(depthBuffer, 0).xy;
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#ifndef COPY_DEPTH
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texelPos *= 2;
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#endif
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float val = sampleLowerMip(texelPos);
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#ifndef COPY_DEPTH
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float val2 = sampleLowerMip(texelPos + ivec2(1, 0));
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float val3 = sampleLowerMip(texelPos + ivec2(1, 1));
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float val4 = sampleLowerMip(texelPos + ivec2(0, 1));
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val = minmax(val, val2);
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val = minmax(val, val3);
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val = minmax(val, val4);
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/* if we are reducing an odd-width texture then fetch the edge texels */
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if (((mipsize.x & 1) != 0) && (texelPos.x == mipsize.x - 3)) {
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/* if both edges are odd, fetch the top-left corner texel */
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if (((mipsize.y & 1) != 0) && (texelPos.y == mipsize.y - 3)) {
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val = minmax(val, sampleLowerMip(texelPos + ivec2(2, 2)));
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}
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float val2 = sampleLowerMip(texelPos + ivec2(2, 0));
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float val3 = sampleLowerMip(texelPos + ivec2(2, 1));
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val = minmax(val, val2);
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val = minmax(val, val3);
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}
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/* if we are reducing an odd-height texture then fetch the edge texels */
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if (((mipsize.y & 1) != 0) && (texelPos.y == mipsize.y - 3)) {
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float val2 = sampleLowerMip(texelPos + ivec2(0, 2));
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float val3 = sampleLowerMip(texelPos + ivec2(1, 2));
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val = minmax(val, val2);
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val = minmax(val, val3);
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}
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#endif
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gl_FragDepth = val;
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} |