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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[]; };
/// LBM constants
uniform uint nX;
uniform uint nY;
const uint q = 9;
/// Data access
float get(uint x, uint y, int i, int j) {
return collideCells[q*nX*y + q*x + (i+1)*3 + j+1];
}
void set(uint x, uint y, int i, int j, float v) {
streamCells[q*nX*y + q*x + (i+1)*3 + j+1] = v;
}
/// Actual stream kernel
void main() {
const uint x = gl_GlobalInvocationID.x;
const uint y = gl_GlobalInvocationID.y;
if ( !(x < nX && y < nY) ) {
return;
}
if ( x != 0 && x != nX-1 && y != 0 && y != nY-1 ) {
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));
}
}
} else {
// rudimentary bounce back boundary handling
for ( int i = -1; i <= 1; ++i ) {
for ( int j = -1; j <= 1; ++j ) {
if ( (x > 0 || i >= 0) && x+i <= nX-1 && (y > 0 || j >= 0) && y+j <= nY-1 ) {
set(x+i,y+j,i,j, get(x,y,i,j));
} else {
set(x,y,i*(-1),j*(-1), get(x,y,i,j));
}
}
}
}
}
)";
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