void make_grid(Vector3f origin, float dx,
int ni, int nj, int nk,
DenseGrid3f scalars)
{
scalars.resize(ni, nj, nk);
scalars.assign(float.MaxValue); // sentinel
if (DebugPrint)
{
System.Console.WriteLine("start");
}
// Ok, because the whole idea is that the surface might have holes, we are going to
// compute values along known triangles and then propagate the computed region outwards
// until any iso-sign-change is surrounded.
// To seed propagation, we compute unsigned SDF and then compute values for any voxels
// containing surface (ie w/ distance smaller than cellsize)
// compute unsigned SDF
var sdf = new MeshSignedDistanceGrid(Mesh, CellSize)
{
ComputeSigns = false
};
sdf.CancelF = this.CancelF;
sdf.Compute();
if (CancelF())
{
return;
}
DenseGrid3f distances = sdf.Grid;
if (WantMeshSDFGrid)
{
mesh_sdf = sdf;
}
if (DebugPrint)
{
System.Console.WriteLine("done initial sdf");
}
// compute values at surface voxels
double ox = (double)origin[0], oy = (double)origin[1], oz = (double)origin[2];
gParallel.ForEach(gIndices.Grid3IndicesYZ(nj, nk), (jk) =>
{
if (CancelF())
{
return;
}
for (int i = 0; i < ni; ++i)
{
var ijk = new Vector3i(i, jk.y, jk.z);
float dist = distances[ijk];
// this could be tighter? but I don't think it matters...
if (dist < CellSize)
{
var gx = new Vector3d((float)ijk.x * dx + origin[0], (float)ijk.y * dx + origin[1], (float)ijk.z * dx + origin[2]);
scalars[ijk] = (float)ScalarF(gx);
}
}
});
if (CancelF())
{
return;
}
if (DebugPrint)
{
System.Console.WriteLine("done narrow-band");
}
// Now propagate outwards from computed voxels.
// Current procedure is to check 26-neighbours around each 'front' voxel,
// and if there are any sign changes, that neighbour is added to front.
// Front is initialized w/ all voxels we computed above
AxisAlignedBox3i bounds = scalars.Bounds;
bounds.Max -= Vector3i.One;
// since we will be computing new values as necessary, we cannot use
// grid to track whether a voxel is 'new' or not.
// So, using 3D bitmap intead - is updated at end of each pass.
var bits = new Bitmap3(new Vector3i(ni, nj, nk));
var cur_front = new List <Vector3i>();
foreach (Vector3i ijk in scalars.Indices())
{
if (scalars[ijk] != float.MaxValue)
{
cur_front.Add(ijk);
bits[ijk] = true;
}
}
if (CancelF())
{
return;
}
// Unique set of 'new' voxels to compute in next iteration.
var queue = new HashSet <Vector3i>();
var queue_lock = new SpinLock();
while (true)
{
if (CancelF())
{
return;
}
// can process front voxels in parallel
bool abort = false; int iter_count = 0;
gParallel.ForEach(cur_front, (ijk) =>
{
Interlocked.Increment(ref iter_count);
if (iter_count % 100 == 0)
{
abort = CancelF();
}
if (abort)
{
return;
}
float val = scalars[ijk];
// check 26-neighbours to see if we have a crossing in any direction
for (int k = 0; k < 26; ++k)
{
Vector3i nijk = ijk + gIndices.GridOffsets26[k];
if (bounds.Contains(nijk) == false)
{
continue;
}
float val2 = scalars[nijk];
if (val2 == float.MaxValue)
{
var gx = new Vector3d((float)nijk.x * dx + origin[0], (float)nijk.y * dx + origin[1], (float)nijk.z * dx + origin[2]);
val2 = (float)ScalarF(gx);
scalars[nijk] = val2;
}
if (bits[nijk] == false)
{
// this is a 'new' voxel this round.
// If we have an iso-crossing, add it to the front next round
bool crossing = (val <IsoValue && val2> IsoValue) ||
(val > IsoValue && val2 < IsoValue);
if (crossing)
{
bool taken = false;
queue_lock.Enter(ref taken);
queue.Add(nijk);
queue_lock.Exit();
}
}
}
});
if (DebugPrint)
{
System.Console.WriteLine("front has {0} voxels", queue.Count);
}
if (queue.Count == 0)
{
break;
}
// update known-voxels list and create front for next iteration
foreach (Vector3i idx in queue)
{
bits[idx] = true;
}
cur_front.Clear();
cur_front.AddRange(queue);
queue.Clear();
}
if (DebugPrint)
{
System.Console.WriteLine("done front-prop");
}
if (DebugPrint)
{
int filled = 0;
foreach (Vector3i ijk in scalars.Indices())
{
if (scalars[ijk] != float.MaxValue)
{
filled++;
}
}
System.Console.WriteLine("filled: {0} / {1} - {2}%", filled, ni * nj * nk,
(double)filled / (double)(ni * nj * nk) * 100.0);
}
if (CancelF())
{
return;
}
// fill in the rest of the grid by propagating know values
fill_spans(ni, nj, nk, scalars);
if (DebugPrint)
{
System.Console.WriteLine("done sweep");
}
}
public static void test_marching_cubes_topology()
{
AxisAlignedBox3d bounds = new AxisAlignedBox3d(1.0);
int numcells = 64;
double cellsize = bounds.MaxDim / numcells;
Random r = new Random(31337);
for (int ii = 0; ii < 100; ++ii)
{
DenseGrid3f grid = new DenseGrid3f();
grid.resize(numcells, numcells, numcells);
grid.assign(1);
for (int k = 2; k < numcells - 3; k++)
{
for (int j = 2; j < numcells - 3; j++)
{
for (int i = 2; i < numcells - 3; i++)
{
double d = r.NextDouble();
if (d > 0.9)
{
grid[i, j, k] = 0.0f;
}
else if (d > 0.5)
{
grid[i, j, k] = 1.0f;
}
else
{
grid[i, j, k] = -1.0f;
}
}
}
}
var iso = new DenseGridTrilinearImplicit(grid, Vector3f.Zero, cellsize);
MarchingCubes c = new MarchingCubes();
c.Implicit = iso;
c.Bounds = bounds;
//c.Bounds.Max += 3 * cellsize * Vector3d.One;
//c.Bounds.Expand(2*cellsize);
// this produces holes
c.CubeSize = cellsize * 4.1;
//c.CubeSize = cellsize * 2;
//c.Bounds = new AxisAlignedBox3d(2.0);
c.Generate();
for (float f = 2.0f; f < 8.0f; f += 0.13107f)
{
c.CubeSize = cellsize * 4.1;
c.Generate();
c.Mesh.CheckValidity(false);
MeshBoundaryLoops loops = new MeshBoundaryLoops(c.Mesh);
if (loops.Count > 0)
{
throw new Exception("found loops!");
}
}
}
//c.Mesh.CheckValidity(false);
//TestUtil.WriteTestOutputMesh(c.Mesh, "marching_cubes_topotest.obj");
}
void generate_support(Vector3f origin, float dx,
int ni, int nj, int nk,
DenseGrid3f supportGrid)
{
supportGrid.resize(ni, nj, nk);
supportGrid.assign(1); // sentinel
if (DebugPrint)
{
System.Console.WriteLine("start");
}
bool CHECKERBOARD = false;
System.Console.WriteLine("Computing SDF");
// compute unsigned SDF
MeshSignedDistanceGrid sdf = new MeshSignedDistanceGrid(Mesh, CellSize)
{
ComputeSigns = true, ExactBandWidth = 3,
/*,ComputeMode = MeshSignedDistanceGrid.ComputeModes.FullGrid*/ };
sdf.CancelF = Cancelled;
sdf.Compute();
if (Cancelled())
{
return;
}
var distanceField = new DenseGridTrilinearImplicit(sdf.Grid, sdf.GridOrigin, sdf.CellSize);
double angle = MathUtil.Clamp(OverhangAngleDeg, 0.01, 89.99);
double cos_thresh = Math.Cos(angle * MathUtil.Deg2Rad);
System.Console.WriteLine("Marking overhangs");
// Compute narrow-band distances. For each triangle, we find its grid-coord-bbox,
// and compute exact distances within that box. The intersection_count grid
// is also filled in this computation
double ddx = (double)dx;
double ox = (double)origin[0], oy = (double)origin[1], oz = (double)origin[2];
Vector3d va = Vector3d.Zero, vb = Vector3d.Zero, vc = Vector3d.Zero;
foreach (int tid in Mesh.TriangleIndices())
{
if (tid % 100 == 0 && Cancelled())
{
break;
}
Mesh.GetTriVertices(tid, ref va, ref vb, ref vc);
Vector3d normal = MathUtil.Normal(ref va, ref vb, ref vc);
if (normal.Dot(-Vector3d.AxisY) < cos_thresh)
{
continue;
}
// real ijk coordinates of va/vb/vc
double fip = (va[0] - ox) / ddx, fjp = (va[1] - oy) / ddx, fkp = (va[2] - oz) / ddx;
double fiq = (vb[0] - ox) / ddx, fjq = (vb[1] - oy) / ddx, fkq = (vb[2] - oz) / ddx;
double fir = (vc[0] - ox) / ddx, fjr = (vc[1] - oy) / ddx, fkr = (vc[2] - oz) / ddx;
// clamped integer bounding box of triangle plus exact-band
int exact_band = 0;
int i0 = MathUtil.Clamp(((int)MathUtil.Min(fip, fiq, fir)) - exact_band, 0, ni - 1);
int i1 = MathUtil.Clamp(((int)MathUtil.Max(fip, fiq, fir)) + exact_band + 1, 0, ni - 1);
int j0 = MathUtil.Clamp(((int)MathUtil.Min(fjp, fjq, fjr)) - exact_band, 0, nj - 1);
int j1 = MathUtil.Clamp(((int)MathUtil.Max(fjp, fjq, fjr)) + exact_band + 1, 0, nj - 1);
int k0 = MathUtil.Clamp(((int)MathUtil.Min(fkp, fkq, fkr)) - exact_band, 0, nk - 1);
int k1 = MathUtil.Clamp(((int)MathUtil.Max(fkp, fkq, fkr)) + exact_band + 1, 0, nk - 1);
// don't put into y=0 plane
if (j0 == 0)
{
j0 = 1;
}
// compute distance for each tri inside this bounding box
// note: this can be very conservative if the triangle is large and on diagonal to grid axes
for (int k = k0; k <= k1; ++k)
{
for (int j = j0; j <= j1; ++j)
{
for (int i = i0; i <= i1; ++i)
{
Vector3d gx = new Vector3d((float)i * dx + origin[0], (float)j * dx + origin[1], (float)k * dx + origin[2]);
float d = (float)MeshSignedDistanceGrid.point_triangle_distance(ref gx, ref va, ref vb, ref vc);
// vertical checkerboard pattern (eg 'tips')
if (CHECKERBOARD)
{
int zz = (k % 2 == 0) ? 1 : 0;
if (i % 2 == zz)
{
continue;
}
}
if (d < dx / 2)
{
if (j > 1)
{
supportGrid[i, j, k] = SUPPORT_TIP_TOP;
supportGrid[i, j - 1, k] = SUPPORT_TIP_BASE;
}
else
{
supportGrid[i, j, k] = SUPPORT_TIP_BASE;
}
}
}
}
}
}
if (Cancelled())
{
return;
}
//process_version1(supportGrid, distanceField);
//process_version2(supportGrid, distanceField);
generate_graph(supportGrid, distanceField);
//Util.WriteDebugMesh(MakeDebugGraphMesh(), "c:\\scratch\\__LAST_GRAPH_INIT.obj");
postprocess_graph();
//Util.WriteDebugMesh(MakeDebugGraphMesh(), "c:\\scratch\\__LAST_GRAPH_OPT.obj");
}
void generate_support(Vector3f origin, float dx,
int ni, int nj, int nk,
DenseGrid3f supportGrid)
{
supportGrid.resize(ni, nj, nk);
supportGrid.assign(1); // sentinel
bool CHECKERBOARD = false;
// compute unsigned SDF
int exact_band = 1;
if (SubtractMesh && SubtractMeshOffset > 0)
{
int offset_band = (int)(SubtractMeshOffset / CellSize) + 1;
exact_band = Math.Max(exact_band, offset_band);
}
sdf = new MeshSignedDistanceGrid(Mesh, CellSize)
{
ComputeSigns = true, ExactBandWidth = exact_band
};
sdf.CancelF = this.CancelF;
sdf.Compute();
if (CancelF())
{
return;
}
var distanceField = new DenseGridTrilinearImplicit(sdf.Grid, sdf.GridOrigin, sdf.CellSize);
double angle = MathUtil.Clamp(OverhangAngleDeg, 0.01, 89.99);
double cos_thresh = Math.Cos(angle * MathUtil.Deg2Rad);
// Compute narrow-band distances. For each triangle, we find its grid-coord-bbox,
// and compute exact distances within that box. The intersection_count grid
// is also filled in this computation
double ddx = (double)dx;
double ox = (double)origin[0], oy = (double)origin[1], oz = (double)origin[2];
Vector3d va = Vector3d.Zero, vb = Vector3d.Zero, vc = Vector3d.Zero;
foreach (int tid in Mesh.TriangleIndices())
{
if (tid % 100 == 0 && CancelF())
{
break;
}
Mesh.GetTriVertices(tid, ref va, ref vb, ref vc);
Vector3d normal = MathUtil.Normal(ref va, ref vb, ref vc);
if (normal.Dot(-Vector3d.AxisY) < cos_thresh)
{
continue;
}
// real ijk coordinates of va/vb/vc
double fip = (va[0] - ox) / ddx, fjp = (va[1] - oy) / ddx, fkp = (va[2] - oz) / ddx;
double fiq = (vb[0] - ox) / ddx, fjq = (vb[1] - oy) / ddx, fkq = (vb[2] - oz) / ddx;
double fir = (vc[0] - ox) / ddx, fjr = (vc[1] - oy) / ddx, fkr = (vc[2] - oz) / ddx;
// clamped integer bounding box of triangle plus exact-band
int extra_band = 0;
int i0 = MathUtil.Clamp(((int)MathUtil.Min(fip, fiq, fir)) - extra_band, 0, ni - 1);
int i1 = MathUtil.Clamp(((int)MathUtil.Max(fip, fiq, fir)) + extra_band + 1, 0, ni - 1);
int j0 = MathUtil.Clamp(((int)MathUtil.Min(fjp, fjq, fjr)) - extra_band, 0, nj - 1);
int j1 = MathUtil.Clamp(((int)MathUtil.Max(fjp, fjq, fjr)) + extra_band + 1, 0, nj - 1);
int k0 = MathUtil.Clamp(((int)MathUtil.Min(fkp, fkq, fkr)) - extra_band, 0, nk - 1);
int k1 = MathUtil.Clamp(((int)MathUtil.Max(fkp, fkq, fkr)) + extra_band + 1, 0, nk - 1);
// don't put into y=0 plane
//if (j0 == 0)
// j0 = 1;
// compute distance for each tri inside this bounding box
// note: this can be very conservative if the triangle is large and on diagonal to grid axes
for (int k = k0; k <= k1; ++k)
{
for (int j = j0; j <= j1; ++j)
{
for (int i = i0; i <= i1; ++i)
{
Vector3d gx = new Vector3d((float)i * dx + origin[0], (float)j * dx + origin[1], (float)k * dx + origin[2]);
float d = (float)MeshSignedDistanceGrid.point_triangle_distance(ref gx, ref va, ref vb, ref vc);
// vertical checkerboard pattern (eg 'tips')
if (CHECKERBOARD)
{
int zz = (k % 2 == 0) ? 1 : 0;
if (i % 2 == zz)
{
continue;
}
}
if (d < dx / 2)
{
supportGrid[i, j, k] = SUPPORT_TIP_TOP;
}
}
}
}
}
if (CancelF())
{
return;
}
fill_vertical_spans(supportGrid, distanceField);
generate_mesh(supportGrid, distanceField);
}