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#ifndef UNITY_VBUFFER_INCLUDED
#define UNITY_VBUFFER_INCLUDED
// Interpolation in the log space is non-linear.
// Therefore, given 'logEncodedDepth', we compute a new depth value
// which allows us to perform HW interpolation which is linear in the view space.
float ComputeLerpPositionForLogEncoding(float linearDepth, float logEncodedDepth,
float4 VBufferScaleAndSliceCount,
float4 VBufferDepthEncodingParams)
{
float z = linearDepth;
float d = logEncodedDepth;
float numSlices = VBufferScaleAndSliceCount.z;
float rcpNumSlices = VBufferScaleAndSliceCount.w;
float s0 = floor(d * numSlices - 0.5);
float s1 = ceil(d * numSlices - 0.5);
float d0 = saturate(s0 * rcpNumSlices + (0.5 * rcpNumSlices));
float d1 = saturate(s1 * rcpNumSlices + (0.5 * rcpNumSlices));
float z0 = DecodeLogarithmicDepth(d0, VBufferDepthEncodingParams);
float z1 = DecodeLogarithmicDepth(d1, VBufferDepthEncodingParams);
// Compute the linear interpolation weight.
float t = saturate((z - z0) / (z1 - z0));
return d0 + t * rcpNumSlices;
}
// Performs trilinear reconstruction of the V-Buffer.
// If (clampToEdge == false), out-of-bounds loads return 0.
float4 SampleVBuffer(TEXTURE3D_ARGS(VBufferLighting, trilinearSampler), bool clampToEdge,
float2 positionNDC, float linearDepth,
float4 VBufferScaleAndSliceCount,
float4 VBufferDepthEncodingParams)
{
float numSlices = VBufferScaleAndSliceCount.z;
float rcpNumSlices = VBufferScaleAndSliceCount.w;
// Account for the visible area of the V-Buffer.
float2 uv = positionNDC * VBufferScaleAndSliceCount.xy;
// The distance between slices is log-encoded.
float z = linearDepth;
float d = EncodeLogarithmicDepth(z, VBufferDepthEncodingParams);
// Unity doesn't support samplers clamping to border, so we have to do it ourselves.
// TODO: add the proper sampler support.
bool isInBounds = Min3(uv.x, uv.y, d) > 0 && Max3(uv.x, uv.y, d) < 1;
[branch] if (clampToEdge || isInBounds)
{
#if 0
// We could ignore non-linearity at the cost of accuracy.
// TODO: visually test this option (especially in motion).
float w = d;
#else
// Adjust the texture coordinate for HW trilinear sampling.
float w = ComputeLerpPositionForLogEncoding(z, d, VBufferScaleAndSliceCount, VBufferDepthEncodingParams);
#endif
return SAMPLE_TEXTURE3D_LOD(VBufferLighting, trilinearSampler, float3(uv, w), 0);
}
else
{
return 0;
}
}
// Returns interpolated {volumetric radiance, opacity}. The sampler clamps to edge.
float4 SampleInScatteredRadianceAndTransmittance(TEXTURE3D_ARGS(VBufferLighting, trilinearSampler),
float2 positionNDC, float linearDepth,
float4 VBufferResolution,
float4 VBufferScaleAndSliceCount,
float4 VBufferDepthEncodingParams)
{
#ifdef RECONSTRUCTION_FILTER_TRILINEAR
float4 L = SampleVBuffer(TEXTURE3D_PARAM(VBufferLighting, trilinearSampler), true,
positionNDC, linearDepth,
VBufferScaleAndSliceCount, VBufferDepthEncodingParams);
#else
// Perform biquadratic reconstruction in XY, linear in Z, using 4x trilinear taps.
// Account for the visible area of the V-Buffer.
float2 xy = positionNDC * (VBufferResolution.xy * VBufferScaleAndSliceCount.xy);
float2 ic = floor(xy);
float2 fc = frac(xy);
// The distance between slices is log-encoded.
float z = linearDepth;
float d = EncodeLogarithmicDepth(z, VBufferDepthEncodingParams);
// Adjust the texture coordinate for HW trilinear sampling.
float w = ComputeLerpPositionForLogEncoding(z, d, VBufferScaleAndSliceCount, VBufferDepthEncodingParams);
float2 weights[2], offsets[2];
BiquadraticFilter(1 - fc, weights, offsets); // Inverse-translate the filter centered around 0.5
float2 rcpRes = VBufferResolution.zw;
// TODO: reconstruction should be performed in the perceptual space (e.i., after tone mapping).
// But our VBuffer is linear. How to achieve that?
// See "A Fresh Look at Generalized Sampling", p. 51.
float4 L = (weights[0].x * weights[0].y) * SAMPLE_TEXTURE3D_LOD(VBufferLighting, trilinearSampler, float3((ic + float2(offsets[0].x, offsets[0].y)) * rcpRes, w), 0) // Top left
+ (weights[1].x * weights[0].y) * SAMPLE_TEXTURE3D_LOD(VBufferLighting, trilinearSampler, float3((ic + float2(offsets[1].x, offsets[0].y)) * rcpRes, w), 0) // Top right
+ (weights[0].x * weights[1].y) * SAMPLE_TEXTURE3D_LOD(VBufferLighting, trilinearSampler, float3((ic + float2(offsets[0].x, offsets[1].y)) * rcpRes, w), 0) // Bottom left
+ (weights[1].x * weights[1].y) * SAMPLE_TEXTURE3D_LOD(VBufferLighting, trilinearSampler, float3((ic + float2(offsets[1].x, offsets[1].y)) * rcpRes, w), 0); // Bottom right
#endif
// TODO: add some animated noise to the reconstructed radiance.
return float4(L.rgb, 1 - Transmittance(L.a));
}
#endif // UNITY_VBUFFER_INCLUDED