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static const std::string INTERACT_SHADER_CODE = R"(
#version 430
layout (local_size_x = 1, local_size_y = 1) in;
layout (std430, binding=3) buffer bufferFluid { float fluidCells[]; };
layout (std430, binding=4) buffer bufferExtra { float extraCells[]; };
uniform uint nX;
uniform uint nY;
/// External influence
uniform bool wall_requested;
uniform bool fluid_requested;
uniform vec2 start;
uniform vec2 end;
/// Vector utilities
float norm(vec2 v) {
return sqrt(dot(v,v));
}
float distanceToLineSegment(vec2 a, vec2 b, vec2 p) {
const vec2 ab = b - a;
const vec2 pa = a - p;
if ( dot(ab, pa) > 0.0 ) {
return norm(pa);
}
const vec2 bp = p - b;
if ( dot(ab, bp) > 0.0 ) {
return norm(bp);
}
return norm(pa - ab * (dot(ab, pa) / dot(ab, ab)));
}
bool isNearLine(uint x, uint y, float eps) {
if ( start == end ) {
return norm(vec2(x,y) - end) < eps;
} else {
return distanceToLineSegment(start, end, vec2(x,y)) < eps;
}
}
/// Array indexing
uint indexOfFluidVertex(uint x, uint y) {
return 3*nX*y + 3*x;
}
/// Data access
int getMaterial(uint x, uint y) {
const uint idx = indexOfFluidVertex(x, y);
return int(fluidCells[idx + 2]);
}
void setMaterial(uint x, uint y, int m) {
const uint idx = indexOfFluidVertex(x, y);
fluidCells[idx + 2] = m;
extraCells[idx + 2] = m;
}
/// Geometry cleanup
void disableWallInterior(uint x, uint y) {
int wallNeighbors = 0;
for ( int i = -1; i <= 1; ++i ) {
for ( int j = -1; j <= 1; ++j ) {
const int material = getMaterial(x+i,y+j);
if ( material == 0 || material == 2 || material == 3 ) {
++wallNeighbors;
}
}
}
if ( wallNeighbors == 9 ) {
setMaterial(x,y,0);
}
}
void fixWallExterior(uint x, uint y) {
for ( int i = -1; i <= 1; ++i ) {
for ( int j = -1; j <= 1; ++j ) {
if ( getMaterial(x+i,y+j)== 0 ) {
setMaterial(x+i,y+j,3);
}
}
}
}
/// Actual interaction 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 == 1 ) {
if ( isNearLine(x, y, 3) ) {
if ( wall_requested ) {
setMaterial(x,y,3);
return;
}
}
}
if ( material == 0 || material == 3 ) {
if ( fluid_requested ) {
if ( isNearLine(x, y, 3) ) {
setMaterial(x,y,1);
fixWallExterior(x,y);
return;
}
}
}
if ( material == 3 ) {
disableWallInterior(x,y);
}
}
)";
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