128 lines
4.2 KiB
Plaintext
128 lines
4.2 KiB
Plaintext
//
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// conventions
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// left = coord.x - 1
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// right = coord.x + 1
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// top = coord.y + 1
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// bottom = coord.y - 1
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//
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//#include "../../../Shaders/NoiseLib/Noise.hlsl"
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//Texture2D<float4> PrecipMask; //defines where rainfall will occur
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Texture2D<float4> ReposeMask;
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Texture2D<float> Collision;
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Texture2D<float> TerrainHeightPrev; //previous frame
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Texture2D<float> SedimentPrev;
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Texture2D<float> Hardness;
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//outputs
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RWTexture2D<float> TerrainHeight; //terrain heightmap
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RWTexture2D<float> Sediment; //suspended sediment concentration (being transported by the water)
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float dt; //the time step for the simulation
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float EffectScalar;
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float4 texDim; //the dimensions of all of our textures (they must all be the same dimensions)
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float3 terrainDim; //the dimensions of the terrain in world units
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#define LEFT(C) C.y
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#define RIGHT(C) C.x
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#define TOP(C) C.z
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#define BOTTOM(C) C.w
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uint4 getSafeNeighbors(uint2 coord) {
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return uint4(
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(coord.x < (uint)texDim[0] - 1) ? coord.x + 1 : coord.x, //right index
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(coord.x > 0) ? coord.x - 1 : coord.x, //left index
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(coord.y < (uint)texDim[1] - 1) ? coord.y + 1 : coord.y, //top index
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(coord.y > 0) ? coord.y - 1 : coord.y //bottom index
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);
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}
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//
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// Thermal Erosion
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//
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float4 angleOfRepose; //actually tan(theta), which is slope (m)
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float4 dxdy; //<dx, dy, 1.0f / dx, 1.0f / dy>
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float InvDiagMag;
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void simulateThermalErosion(uint2 coord) {
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uint4 neigh = getSafeNeighbors(coord);
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float4 hCardinal = float4(TerrainHeightPrev[uint2(LEFT(neigh), coord.y)], //left
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TerrainHeightPrev[uint2(RIGHT(neigh), coord.y)], //right
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TerrainHeightPrev[uint2(coord.x, TOP(neigh))], //up
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TerrainHeightPrev[uint2(coord.x, BOTTOM(neigh))]); //down
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float4 hDiagonal = float4(TerrainHeightPrev[uint2(LEFT(neigh), TOP(neigh))], //top left
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TerrainHeightPrev[uint2(RIGHT(neigh), TOP(neigh))], //top right
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TerrainHeightPrev[uint2(LEFT(neigh), BOTTOM(neigh))], //bottom left
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TerrainHeightPrev[uint2(RIGHT(neigh), BOTTOM(neigh))]); //bottom right
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/*
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float4 hardnessCardinal = saturate(float4(Hardness[uint2(neigh.y, coord.y)],
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Hardness[uint2(neigh.x, coord.y)],
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Hardness[uint2(coord.x, neigh.z)],
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Hardness[uint2(coord.x, neigh.w)]));
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float4 hardnessDiagonal = saturate(float4(Hardness[uint2(neigh.y, neigh.z)],
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Hardness[uint2(neigh.x, neigh.z)],
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Hardness[uint2(neigh.y, neigh.w)],
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Hardness[uint2(neigh.x, neigh.w)]));
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*/
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float4 h = float4(TerrainHeightPrev[coord], TerrainHeightPrev[coord], TerrainHeightPrev[coord], TerrainHeightPrev[coord]);
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float4 dhCardinal = terrainDim[1] * (h - hCardinal);
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float4 dhDiagonal = terrainDim[1] * (h - hDiagonal);
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float4 sCardinal = -1.0f * min(sign(dhCardinal), 0.0f);
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float4 sDiagonal = -1.0f * min(sign(dhDiagonal), 0.0f);
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/*
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float4 cHardness = saturate(Hardness[coord]);
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float4 hardness = lerp(cHardness, hardnessCardinal, sCardinal);
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dhCardinal *= 1.0f - hardness;
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hardness = lerp(cHardness, hardnessDiagonal, sDiagonal);
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dhDiagonal *= 1.0f - hardness;
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*/
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//compute slopes
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float4 mCardinal = abs(dhCardinal * float4(dxdy.z, dxdy.z, dxdy.w, dxdy.w));
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float4 mDiagonal = abs(dhDiagonal * float4(InvDiagMag, InvDiagMag, InvDiagMag, InvDiagMag));
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float tau = angleOfRepose.x;
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float dv = 0.0f; //volume of sediment moved
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//could probably vectorize this and eliminate the ifs...
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if (mCardinal.x > tau) { dv += dhCardinal.x; }
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if (mCardinal.y > tau) { dv += dhCardinal.y; }
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if (mCardinal.z > tau) { dv += dhCardinal.z; }
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if (mCardinal.w > tau) { dv += dhCardinal.w; }
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if (mDiagonal.x > tau) { dv += 0.707f * dhDiagonal.x; }
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if (mDiagonal.y > tau) { dv += 0.707f * dhDiagonal.y; }
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if (mDiagonal.z > tau) { dv += 0.707f * dhDiagonal.z; }
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if (mDiagonal.w > tau) { dv += 0.707f * dhDiagonal.w; }
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float halfHeight = 0.5f * TerrainHeightPrev[coord];
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dv = clamp(0.0625f * dt * dv, -halfHeight, halfHeight);
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TerrainHeight[coord] = TerrainHeightPrev[coord] - dv;
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Sediment[coord] += dv;
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}
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#pragma kernel ThermalErosion
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[numthreads(8, 8, 1)]
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void ThermalErosion(uint3 id : SV_DispatchThreadID)
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{
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simulateThermalErosion(id.xy);
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}
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