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=4) buffer bufferGeometry { int   materialCells[]; };

/// 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;
}

/// 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) {
	return materialCells[nX*y + x];
}

/// Domain description

bool isEndOfWorld(uint x, uint y) {
	return x == 0 || x == nX-1 || y == 0 || y == nY-1;
}

bool isOuterWall(uint x, uint y) {
	return x == 1 || x == nX-2 || y == 1 || y == nY-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 ) {
		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));
		}
	}
}
)";