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static const std::string STREAM_SHADER_CODE = R"(
#version 430
layout (local_size_x = 1, local_size_y = 1) in;
layout (std430, binding=1) buffer bufferCollide { float collideCells[]; };
layout (std430, binding=2) buffer bufferStream { float streamCells[]; };
layout (std430, binding=3) buffer bufferFluid { float fluidCells[]; };
/// LBM constants
uniform uint nX;
uniform uint nY;
const uint q = 9;
// Array indexing
uint indexOfDirection(int i, int j) {
return 3*(i+1) + (j+1);
}
uint indexOfLatticeCell(uint x, uint y) {
return q*nX*y + q*x;
}
uint indexOfFluidVertex(uint x, uint y) {
return 3*nX*y + 3*x;
}
/// Data access
float get(uint x, uint y, int i, int j) {
return collideCells[indexOfLatticeCell(x,y) + indexOfDirection(i,j)];
}
void set(uint x, uint y, int i, int j, float v) {
streamCells[indexOfLatticeCell(x,y) + indexOfDirection(i,j)] = v;
}
int getMaterial(uint x, uint y) {
const uint idx = indexOfFluidVertex(x, y);
return int(fluidCells[idx + 2]);
}
/// Boundary conditions
void bounceBack(uint x, uint y) {
for ( int i = -1; i <= 1; ++i ) {
for ( int j = -1; j <= 1; ++j ) {
set(x,y,i,j, get(x,y,(-1)*i,(-1)*j));
}
}
}
/// Actual stream kernel
void main() {
const uint x = gl_GlobalInvocationID.x;
const uint y = gl_GlobalInvocationID.y;
if ( !(x < nX && y < nY) ) {
return;
}
const int material = getMaterial(x,y);
if ( material == 0 ) {
return;
}
if ( material == 2 || material == 3 ) {
bounceBack(x,y);
}
for ( int i = -1; i <= 1; ++i ) {
for ( int j = -1; j <= 1; ++j ) {
set(x+i,y+j,i,j, get(x,y,i,j));
}
}
}
)";
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