33 lines
1.1 KiB
HLSL
33 lines
1.1 KiB
HLSL
#ifndef UNIVERSAL_SPEEDTREE_UTILITY
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#define UNIVERSAL_SPEEDTREE_UTILITY
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uint2 ComputeFadeMaskSeed(float3 V, uint2 positionSS)
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{
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uint2 fadeMaskSeed;
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// Is this a reasonable quality gate?
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if (IsPerspectiveProjection())
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{
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// Start with the world-space direction V. It is independent from the orientation of the camera,
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// and only depends on the position of the camera and the position of the fragment.
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// Now, project and transform it into [-1, 1].
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float2 pv = PackNormalOctQuadEncode(V);
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// Rescale it to account for the resolution of the screen.
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pv *= _ScreenParams.xy;
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// The camera only sees a small portion of the sphere, limited by hFoV and vFoV.
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// Therefore, we must rescale again (before quantization), roughly, by 1/tan(FoV/2).
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pv *= UNITY_MATRIX_P._m00_m11;
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// Truncate and quantize.
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fadeMaskSeed = asuint((int2)pv);
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}
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else
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{
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// Can't use the view direction, it is the same across the entire screen.
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fadeMaskSeed = positionSS;
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}
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return fadeMaskSeed;
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}
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#endif
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