39 lines
1.3 KiB
Plaintext
39 lines
1.3 KiB
Plaintext
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// Projection Step (hodge decomposition)
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// Requires 2 additional kernels - one to compute the divergence field and
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// one to subtract the gradient
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RWTexture2D<float2> VelocityTex2D;
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RWTexture2D<float2> VelocityOutTex2D;
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RWTexture2D<float> DivergenceTex2D;
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RWTexture2D<float> PressureTex2D;
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RWTexture2D<float> OutputTex2D;
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float4 dxdy; //(dx, dy, 1 / dx, 1 / dy), where dx = cell width, dy = cell height
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#pragma kernel Divergence
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[numthreads(1, 1, 1)]
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void Divergence(uint3 id : SV_DispatchThreadID)
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{
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float2 l = VelocityTex2D[uint2(id.x - 1, id.y)];
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float2 r = VelocityTex2D[uint2(id.x + 1, id.y)];
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float2 b = VelocityTex2D[uint2(id.x, id.y - 1)];
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float2 t = VelocityTex2D[uint2(id.x, id.y + 1)];
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//assumes square resolution & tile dimensions :(
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DivergenceTex2D[id.xy] = 0.5f * dxdy.z * ((r.x - l.x) + (t.y - b.y));
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}
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#pragma kernel GradientSubtract
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[numthreads(1, 1, 1)]
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void GradientSubtract(uint3 id : SV_DispatchThreadID)
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{
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float l = PressureTex2D[uint2(id.x - 1, id.y)];
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float r = PressureTex2D[uint2(id.x + 1, id.y)];
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float b = PressureTex2D[uint2(id.x, id.y - 1)];
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float t = PressureTex2D[uint2(id.x, id.y + 1)];
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//assumes square resolution & tile dimensions. :(
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VelocityOutTex2D[id.xy] = VelocityTex2D[id.xy] - 0.5f * dxdy.z * float2(r - l, t - b);
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}
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