58 lines
1.8 KiB
Python
58 lines
1.8 KiB
Python
/*
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* Copyright 2014 Stanlo Slasinski. All rights reserved.
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* License: http://www.opensource.org/licenses/BSD-2-Clause
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*/
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#include "bgfx_compute.sh"
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#include "uniforms.sh"
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BUFFER_RO(prevPositionBuffer, vec4, 0);
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BUFFER_RO(currPositionBuffer, vec4, 1);
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BUFFER_WR(outPrevPositionBuffer, vec4, 2);
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BUFFER_WR(outCurrPositionBuffer, vec4, 3);
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#define GROUP_SIZE 512
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SHARED vec3 otherEntries[GROUP_SIZE];
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vec3 calcAcceleration(vec3 _currPosition, vec3 _otherPosition)
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{
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vec3 difference = _otherPosition - _currPosition;
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float dist2 = dot(difference, difference);
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float dist6 = dist2 * dist2 * dist2;
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float invDist3 = 1.0 / (sqrt(dist6) + 0.1);
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return u_gravity * u_gravity * invDist3 * difference;
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}
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NUM_THREADS(GROUP_SIZE, 1, 1)
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void main()
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{
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vec3 prevPosition = prevPositionBuffer[gl_GlobalInvocationID.x].xyz;
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vec3 currPosition = currPositionBuffer[gl_GlobalInvocationID.x].xyz;
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vec3 newAcceleration = vec3_splat(0.0);
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for (int j = 0; j < int(u_dispatchSize); ++j)
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{
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otherEntries[gl_LocalInvocationIndex] = currPositionBuffer[j * GROUP_SIZE + int(gl_LocalInvocationIndex)].xyz;
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barrier();
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for (int i = 0; i < GROUP_SIZE; ++i)
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{
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newAcceleration += calcAcceleration(currPosition, otherEntries[i]);
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}
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}
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newAcceleration += (prevPosition - currPosition) * u_damping;
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float accelerationMagnitude = length(newAcceleration);
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float color = pow(min(accelerationMagnitude / 3.0, 1.0), 0.25);
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if (accelerationMagnitude > 0.0)
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{
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newAcceleration = normalize(newAcceleration) * min(accelerationMagnitude, u_maxAcceleration);
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}
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vec3 newPosition = 2.0 * currPosition - prevPosition + newAcceleration * u_timeStep;
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outPrevPositionBuffer[gl_GlobalInvocationID.x] = vec4(currPosition, 0.0);
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outCurrPositionBuffer[gl_GlobalInvocationID.x] = vec4(newPosition, color);
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}
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