//Apply several iterations of a very simple propagation of valid velocity data in all directions
void extrapolate(Array3f& grid, Array3c& valid) {
Array3f temp_grid = grid;
Array3c old_valid(valid.ni,valid.nj,valid.nk);
for(int layers = 0; layers < 10; ++layers) {
old_valid = valid;
for(int k = 1; k < grid.nk-1; ++k) for(int j = 1; j < grid.nj-1; ++j) for(int i = 1; i < grid.ni-1; ++i) {
float sum = 0;
int count = 0;
if(!old_valid(i,j,k)) {
if(old_valid(i+1,j,k)) {
sum += grid(i+1,j,k);
++count;
}
if(old_valid(i-1,j,k)) {
sum += grid(i-1,j,k);
++count;
}
if(old_valid(i,j+1,k)) {
sum += grid(i,j+1,k);
++count;
}
if(old_valid(i,j-1,k)) {
sum += grid(i,j-1,k);
++count;
}
if(old_valid(i,j,k+1)) {
sum += grid(i,j,k+1);
++count;
}
if(old_valid(i,j,k-1)) {
sum += grid(i,j,k-1);
++count;
}
//If any of neighbour cells were valid,
//assign the cell their average value and tag it as valid
if(count > 0) {
temp_grid(i,j,k) = sum /(float)count;
valid(i,j,k) = 1;
}
}
}
grid = temp_grid;
}
}
//Apply several iterations of a very simple "Jacobi"-style propagation of valid velocity data in all directions
void extrapolate(Array2f& grid, const Array2f& grid_weight, Array2c& valid, Array2c old_valid) {
//Initialize the list of valid cells
for(int j = 0; j < grid.nj; ++j) for(int i = 0; i < grid.ni; ++i)
valid(i,j) = grid_weight(i,j) > 0;
for(int layers = 0; layers < 5; ++layers) {
old_valid = valid;
Array2f temp_grid = grid;
for(int j = 1; j < grid.nj-1; ++j) for(int i = 1; i < grid.ni-1; ++i) {
float sum = 0;
int count = 0;
if(!old_valid(i,j)) {
if(old_valid(i+1,j)) {
sum += grid(i+1,j);\
++count;
}
if(old_valid(i-1,j)) {
sum += grid(i-1,j);\
++count;
}
if(old_valid(i,j+1)) {
sum += grid(i,j+1);\
++count;
}
if(old_valid(i,j-1)) {
sum += grid(i,j-1);\
++count;
}
//If any of neighbour cells were valid,
//assign the cell their average value and tag it as valid
if(count > 0) {
temp_grid(i,j) = sum /(float)count;
valid(i,j) = 1;
}
}
}
grid = temp_grid;
}
}