96 lines
2.9 KiB
GLSL
96 lines
2.9 KiB
GLSL
/**
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* Shader that down-sample 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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# define gatherLowerMip(t) textureGather(depthBuffer, vec3(t, depthLayer))
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#else
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# define sampleLowerMip(t) texelFetch(depthBuffer, t, 0).r
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# define gatherLowerMip(t) textureGather(depthBuffer, t)
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#endif
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#ifdef MIN_PASS
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# define minmax2(a, b) min(a, b)
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# define minmax3(a, b, c) min(min(a, b), c)
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# define minmax4(a, b, c, d) min(min(min(a, b), c), d)
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#else /* MAX_PASS */
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# define minmax2(a, b) max(a, b)
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# define minmax3(a, b, c) max(max(a, b), c)
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# define minmax4(a, b, c, d) max(max(max(a, b), c), d)
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#endif
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/* On some AMD card / driver combination, it is needed otherwise,
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* the shader does not write anything. */
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#if defined(GPU_INTEL) || defined(GPU_ATI)
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out vec4 fragColor;
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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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#ifdef COPY_DEPTH
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float val = sampleLowerMip(texelPos);
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#else
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vec4 samp;
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# ifdef GPU_ARB_texture_gather
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/* + 1.0 to gather at the center of target 4 texels. */
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samp = gatherLowerMip((vec2(texelPos) + 1.0) / vec2(mipsize));
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# else
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samp.x = sampleLowerMip(texelPos);
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samp.y = sampleLowerMip(texelPos + ivec2(1, 0));
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samp.z = sampleLowerMip(texelPos + ivec2(1, 1));
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samp.w = sampleLowerMip(texelPos + ivec2(0, 1));
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# endif
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float val = minmax4(samp.x, samp.y, samp.z, samp.w);
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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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samp.x = sampleLowerMip(texelPos + ivec2(2, 2));
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val = minmax2(val, samp.x);
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}
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# ifdef GPU_ARB_texture_gather
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samp = gatherLowerMip((vec2(texelPos) + vec2(2.0, 1.0)) / vec2(mipsize));
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# else
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samp.y = sampleLowerMip(texelPos + ivec2(2, 0));
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samp.z = sampleLowerMip(texelPos + ivec2(2, 1));
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# endif
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val = minmax3(val, samp.y, samp.z);
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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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# ifdef GPU_ARB_texture_gather
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samp = gatherLowerMip((vec2(texelPos) + vec2(1.0, 2.0)) / vec2(mipsize));
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# else
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samp.x = sampleLowerMip(texelPos + ivec2(0, 2));
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samp.y = sampleLowerMip(texelPos + ivec2(1, 2));
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# endif
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val = minmax3(val, samp.x, samp.y);
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}
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#endif
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#if defined(GPU_INTEL) || defined(GPU_ATI)
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/* Use color format instead of 24bit depth texture */
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fragColor = vec4(val);
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#endif
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gl_FragDepth = val;
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}
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