static void skeletonize_pass(DenseGrid2i grid, DenseGrid2i tmp, int iter)
{
int ni = grid.ni, nj = grid.nj;
for (int i = 1; i < ni - 1; i++) {
for (int j = 1; j < nj - 1; j++) {
int p2 = grid[i - 1, j];
int p3 = grid[i - 1, j + 1];
int p4 = grid[i, j + 1];
int p5 = grid[i + 1, j + 1];
int p6 = grid[i + 1, j];
int p7 = grid[i + 1, j - 1];
int p8 = grid[i, j - 1];
int p9 = grid[i - 1, j - 1];
int A = ((p2 == 0 && p3 == 1) ? 1 : 0)
+ ((p3 == 0 && p4 == 1) ? 1 : 0)
+ ((p4 == 0 && p5 == 1) ? 1 : 0)
+ ((p5 == 0 && p6 == 1) ? 1 : 0)
+ ((p6 == 0 && p7 == 1) ? 1 : 0)
+ ((p7 == 0 && p8 == 1) ? 1 : 0)
+ ((p8 == 0 && p9 == 1) ? 1 : 0)
+ ((p9 == 0 && p2 == 1) ? 1 : 0);
int B = p2 + p3 + p4 + p5 + p6 + p7 + p8 + p9;
int m1 = iter == 0 ? (p2 * p4 * p6) : (p2 * p4 * p8);
int m2 = iter == 0 ? (p4 * p6 * p8) : (p2 * p6 * p8);
if (A == 1 && B >= 2 && B <= 6 && m1 == 0 && m2 == 0) {
tmp[i, j] = 1;
}
}
}
for (int i = 0; i < ni; ++i)
for (int j = 0; j < nj; ++j)
grid[i,j] = grid[i, j] & ~tmp[i, j];
}
static void dilate(DenseGrid2i grid, DenseGrid2i tmp, bool corners = true)
{
if (tmp == null)
tmp = new DenseGrid2i(grid.ni, grid.nj, 0);
int ni = grid.ni, nj = grid.nj;
for (int i = 1; i < ni - 1; i++) {
for (int j = 1; j < nj - 1; j++) {
if ( grid[i,j] == 1 ) {
tmp[i, j] = 1;
tmp[i - 1, j] = 1;
tmp[i, j + 1] = 1;
tmp[i + 1, j] = 1;
tmp[i, j - 1] = 1;
if (corners) {
tmp[i - 1, j + 1] = 1;
tmp[i + 1, j + 1] = 1;
tmp[i + 1, j - 1] = 1;
tmp[i - 1, j - 1] = 1;
}
}
}
}
grid.copy(tmp);
}
static void skeletonize_layer(DenseGrid3i grid, int j, int dilation_rounds = 1)
{
DenseGrid2i layer = grid.get_slice(j, 1);
DenseGrid2i tmp = new DenseGrid2i(layer.ni, layer.nj, 0);
for (int k = 0; k < dilation_rounds; ++k) {
tmp.assign(0);
dilate(layer, tmp);
}
bool done = false;
while (!done) {
int sum_before = layer.sum();
tmp.assign(0);
skeletonize_pass(layer, tmp, 0);
tmp.assign(0);
skeletonize_pass(layer, tmp, 1);
int sum_after = layer.sum();
if (sum_before == sum_after)
break;
}
for (int i = 0; i < grid.ni; ++i)
for (int k = 0; k < grid.nk; ++k)
grid[i, j, k] = layer[i, k];
}
static DenseGrid2i binarize(DenseGrid2f grid, float thresh = 0)
{
DenseGrid2i result = new DenseGrid2i();
result.resize(grid.ni, grid.nj);
int size = result.size;
for (int k = 0; k < size; ++k)
result[k] = (grid[k] < thresh) ? 1 : 0;
return result;
}
bool is_loner(DenseGrid2i grid, int i, int j)
{
if (grid[i, j] == 0)
return false;
int nbrs =
grid[i - 1, j] + grid[i - 1, j + 1]
+ grid[i, j + 1] + grid[i + 1, j + 1]
+ grid[i + 1, j] + grid[i + 1, j - 1]
+ grid[i, j - 1] + grid[i - 1, j - 1];
return nbrs == 0;
}
public DenseGrid2i get_slice(int slice_i, int dimension)
{
DenseGrid2i slice;
if (dimension == 0)
{
slice = new DenseGrid2i(nj, nk, 0);
for (int k = 0; k < nk; ++k)
{
for (int j = 0; j < nj; ++j)
{
slice[j, k] = Buffer[slice_i + ni * (j + nj * k)];
}
}
}
else if (dimension == 1)
{
slice = new DenseGrid2i(ni, nk, 0);
for (int k = 0; k < nk; ++k)
{
for (int i = 0; i < ni; ++i)
{
slice[i, k] = Buffer[i + ni * (slice_i + nj * k)];
}
}
}
else
{
slice = new DenseGrid2i(ni, nj, 0);
for (int j = 0; j < nj; ++j)
{
for (int i = 0; i < ni; ++i)
{
slice[i, j] = Buffer[i + ni * (j + nj * slice_i)];
}
}
}
return(slice);
}
static void skeletonize(DenseGrid2i grid, DenseGrid2i tmp, int dilation_rounds = 1)
{
if ( tmp == null )
tmp = new DenseGrid2i(grid.ni, grid.nj, 0);
for (int k = 0; k < dilation_rounds; ++k) {
tmp.clear();
dilate(grid, tmp);
}
bool done = false;
while (!done) {
int sum_before = grid.sum();
tmp.clear();
skeletonize_pass(grid, tmp, 0);
tmp.clear();
skeletonize_pass(grid, tmp, 1);
int sum_after = grid.sum();
if (sum_before == sum_after)
break;
}
}
static void dilate_loners(DenseGrid2i grid, DenseGrid2i tmp, int mode)
{
if (tmp == null)
tmp = new DenseGrid2i(grid.ni, grid.nj, 0);
int ni = grid.ni, nj = grid.nj;
for (int i = 1; i < ni - 1; i++) {
for (int j = 1; j < nj - 1; j++) {
if (grid[i, j] == 1) {
tmp[i, j] = 1;
int nbrs =
grid[i - 1, j] + grid[i - 1, j + 1]
+ grid[i, j + 1] + grid[i + 1, j + 1]
+ grid[i + 1, j] + grid[i + 1, j - 1]
+ grid[i, j - 1] + grid[i - 1, j - 1];
if (nbrs == 0) {
if (mode != 3) {
tmp[i - 1, j] = 1;
tmp[i + 1, j] = 1;
tmp[i, j + 1] = 1;
tmp[i, j - 1] = 1;
}
if (mode == 2 || mode == 3) {
tmp[i - 1, j + 1] = 1;
tmp[i + 1, j + 1] = 1;
tmp[i + 1, j - 1] = 1;
tmp[i - 1, j - 1] = 1;
}
}
}
}
}
grid.copy(tmp);
}
void process_version2(DenseGrid3f supportGrid, DenseGridTrilinearImplicit distanceField)
{
int ni = supportGrid.ni, nj = supportGrid.nj, nk = supportGrid.nk;
float dx = (float)CellSize;
Vector3f origin = this.GridOrigin;
// sweep values down layer by layer
DenseGrid2f prev = supportGrid.get_slice(nj - 1, 1);
DenseGrid2f tmp = new DenseGrid2f(prev);
Bitmap3 bmp = new Bitmap3(new Vector3i(ni, nj, nk));
for (int j = nj - 2; j >= 0; j--) {
// skeletonize prev layer
DenseGrid2i prev_skel = binarize(prev, 0.0f);
skeletonize(prev_skel, null, 2);
//dilate_loners(prev_skel, null, 2);
if (j == 0) {
dilate(prev_skel, null, true);
dilate(prev_skel, null, true);
}
for (int k = 1; k < nk - 1; ++k) {
for (int i = 1; i < ni - 1; ++i)
bmp[new Vector3i(i,j,k)] = (prev_skel[i, k] == 1) ? true : false;
}
smooth(prev, tmp, 0.5f, 5);
DenseGrid2f cur = supportGrid.get_slice(j, 1);
cur.set_min(prev);
for (int k = 1; k < nk - 1; ++k) {
for (int i = 1; i < ni - 1; ++i) {
float skelf = prev_skel[i, k] > 0 ? -1.0f : int.MaxValue;
cur[i, k] = Math.Min(cur[i, k], skelf);
if (cur[i, k] < 0) {
Vector3d cell_center = new Vector3f(i * dx, j * dx, k * dx) + origin;
if (distanceField.Value(ref cell_center) < -CellSize)
cur[i, k] = 1;
}
}
}
for (int k = 1; k < nk - 1; ++k) {
for (int i = 1; i < ni - 1; ++i) {
if (is_loner(prev_skel, i, k)) {
foreach (Vector2i d in gIndices.GridOffsets8) {
float f = 1.0f / (float)Math.Sqrt(d.x*d.x + d.y*d.y);
cur[i + d.x, k + d.y] += -0.25f * f;
}
}
}
}
for (int k = 1; k < nk - 1; ++k) {
for (int i = 1; i < ni - 1; ++i) {
supportGrid[i, j, k] = cur[i, k];
}
}
prev.swap(cur);
}
VoxelSurfaceGenerator gen = new VoxelSurfaceGenerator() { Voxels = bmp };
gen.Generate();
Util.WriteDebugMesh(gen.Meshes[0], "c:\\scratch\\binary.obj");
}
public void copy(DenseGrid2i copy)
{
Array.Copy(copy.Buffer, this.Buffer, this.Buffer.Length);
}
public DenseGrid2i(DenseGrid2i copy)
{
resize(copy.ni, copy.nj);
Array.Copy(copy.Buffer, this.Buffer, this.Buffer.Length);
}