public void Generate(IsoSurface isoSurface, TriangleMesh mesh)
{
if (isoSurface.Threshold > 0.0f)
{
WindingOrder[0] = 0;
WindingOrder[1] = 1;
WindingOrder[2] = 2;
}
else
{
WindingOrder[0] = 2;
WindingOrder[1] = 1;
WindingOrder[2] = 0;
}
for (int x = 0; x < isoSurface.Width - 1; x++)
{
for (int y = 0; y < isoSurface.Height - 1; y++)
{
for (int z = 0; z < isoSurface.Depth - 1; z++)
{
//Get the values in the 8 neighbours which make up a cube
for (int i = 0; i < 8; i++)
{
int ix = x + VertexOffset[i, 0];
int iy = y + VertexOffset[i, 1];
int iz = z + VertexOffset[i, 2];
Cube[i] = isoSurface.Voxels[ix][iy][iz];
}
//Perform algorithm
March(isoSurface.Threshold, isoSurface.Dx, isoSurface.Dy, isoSurface.Dz, Cube, mesh);
}
}
}
}
/// <summary> /// MarchCube performs the Marching algorithm on a single cube /// </summary> protected abstract void March(double threshold, double cx, double cy, double cz, Voxel[] cube, TriangleMesh mesh);
/// <summary>
/// MarchCube performs the Marching Cubes algorithm on a single cube
/// </summary>
protected override void March(double threshold, double cx, double cy, double cz, Voxel[] cube, TriangleMesh mesh)
{
//Find which vertices are inside of the surface and which are outside
int flagIndex = 0;
for (int i = 0; i < cube.Length; i++)
{
if (cube[i].Value <= threshold)
{
flagIndex |= 1 << i;
}
}
//Find which edges are intersected by the surface
int edgeFlags = CubeEdgeFlags[flagIndex];
//If the cube is entirely inside or outside of the surface, then there will be no intersections
if (edgeFlags == 0)
{
return;
}
double x0 = cube[0].X;
double y0 = cube[0].Y;
double z0 = cube[0].Z;
//Find the point of intersection of the surface with each edge
for (int i = 0; i < EdgeVertex.Length; i++)
{
//if there is an intersection on this edge
if ((edgeFlags & (1 << i)) != 0)
{
var index0 = EdgeConnection[i, 0];
var index1 = EdgeConnection[i, 1];
var voxel0 = cube[index0];
var voxel1 = cube[index1];
double v0 = voxel0.Value;
double v1 = voxel1.Value;
var offset = GetOffset(v0, v1, threshold);
var dx = VertexOffset[index0, 0];
var dy = VertexOffset[index0, 1];
var dz = VertexOffset[index0, 2];
var xx = x0 + cx * (dx + offset * EdgeDirection[i, 0]);
var yy = y0 + cy * (dy + offset * EdgeDirection[i, 1]);
var zz = z0 + cz * (dz + offset * EdgeDirection[i, 2]);
EdgeVertex[i] = Helper.CreatePoint(xx, yy, zz);
}
}
//Save the triangles that were found. There can be up to five per cube
var triangles = TriangleConnectionTable[flagIndex];
for (int i = 0; i < triangles.Length; i++)
{
var triplet = triangles[i];
var p1 = EdgeVertex[triplet.Index0];
var p2 = EdgeVertex[triplet.Index1];
var p3 = EdgeVertex[triplet.Index2];
if (p1.Equals(p2) || p1.Equals(p3) || p2.Equals(p3))
{
continue;
}
var idx = mesh.Vertices.Count;
mesh.Triplets.Add(new Triplet(idx + WindingOrder[0], idx + WindingOrder[1], idx + WindingOrder[2]));
mesh.Vertices.Add(p1);
mesh.Vertices.Add(p2);
mesh.Vertices.Add(p3);
}
}
