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05baa0db8a
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e2bf29bf75
9 changed files with 29 additions and 283 deletions
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#version 430 |
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#extension GL_ARB_gpu_shader_fp64 : enable |
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#define MAX_SEGMENTS 32 |
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layout (local_size_x=MAX_SEGMENTS, local_size_y=1, local_size_z=1) in; |
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layout(std430, binding = 0) buffer PositionBuffer { |
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dvec2 X[]; |
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}; |
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layout(std430, binding = 1) buffer VelocityBuffer { |
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dvec2 V[]; |
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}; |
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layout(std430, binding = 2) buffer InverseMassBuffer { |
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double W[]; |
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}; |
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layout(std430, binding = 3) buffer LengthBuffer { |
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double L[]; |
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}; |
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layout(std430, binding = 4) buffer IndexBuffer { |
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uint indices[]; |
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}; |
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layout(std430, binding = 5) buffer SegmentCountBuffer { |
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uint segmentCounts[]; |
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}; |
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uniform double h; |
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uniform double gravity; |
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uniform uint substeps; |
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shared dvec2 P[MAX_SEGMENTS]; |
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// distance constraint |
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void solveConstraint(uint segmentId, uint gIndex){ |
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double w1 = segmentId == 0 ? 0.0 : W[gIndex - 1]; |
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double w2 = W[gIndex]; |
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dvec2 s = (segmentId == 0 ? dvec2(0, 0) : P[segmentId - 1]) - P[segmentId]; |
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dvec2 n = normalize(s); |
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double l = length(s); |
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dvec2 deltaP1 = n * -w1 / (w1 + w2) * (l - L[gIndex]); |
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dvec2 deltaP2 = n * w2 / (w1 + w2) * (l - L[gIndex]); |
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if (segmentId > 0) |
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P[segmentId - 1] += deltaP1; |
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P[segmentId] += deltaP2; |
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} |
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// No need for synchronization, because each pendulum gets its own warp |
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void main() { |
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uint pendulumId = gl_WorkGroupID.x; |
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uint i_off = indices[pendulumId]; |
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uint segmentCount = segmentCounts[pendulumId]; |
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uint localId = gl_LocalInvocationID.x; |
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uint gIndex = i_off + localId; |
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// discard unneeded local threads for segments |
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if (localId >= segmentCount) |
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return; |
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// substepping is not parallelizable |
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for (int k = 0; k < substeps; k++){ |
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// explicit integration with gravity as external force |
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V[gIndex] = V[gIndex] + dvec2(0, -gravity * h); |
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P[localId] = X[gIndex] + V[gIndex] * h; |
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// every segment depends on its neighbour, so we can not parallelize all constraints |
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// only parallelize those, who are independent of each other, skipping every second segment |
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if (localId % 2 == 0){ |
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solveConstraint(localId, i_off + localId); |
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if (localId + 1 < segmentCount) |
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solveConstraint(localId + 1, gIndex + 1); |
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} |
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// update position and velocity |
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V[gIndex] = (P[localId] - X[gIndex]) / h; |
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X[gIndex] = P[localId]; |
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} |
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} |
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