Marching Cubes (C++ to C#)

Question

I am trying to implement marching cubes in C#, but I've come to a part where I don't understand the algorithm and I don't how to implement it.

int Polygonise(GRIDCELL grid, double isolevel, TRIANGLE *triangles)

The third argument I don't really understand. I know it's a pointer, but later on in the algo, when you set the triangles it appears as though the triangles variable is an array of the TRIANGLE struct:

int ntriang = 0;

for (int i=0; triTable[cubeindex,i]!=-1; i+=3) {
    triangles[ntriang].p[i  ] = vertlist[triTable[cubeindex,i  ]];
    triangles[ntriang].p[i+1] = vertlist[triTable[cubeindex,i+1]];
    triangles[ntriang].p[i+2] = vertlist[triTable[cubeindex,i+2]];
    ntriang++;
}

Notice the triangles[ntriang]. That doesn't make sense because before we set triangles to TRIANGLE *triangles. I also don't understand why It's a pointer.

Why doesn't `triangles[ntriang]` make sense? It simply uses `ntriang` to index into the array pointed to by `triangles`. The rest of the expression assigns something to the member `p` of the struct at the `ntriang-th` position. — pmr, Jul 18 '12 at 12:38

Felice Pollano · Accepted Answer · 2014-04-09T05:12:43.593

2

The caller of Polygonize expects *triangles point to an allocated array long enough to contain all the triangles. The equivalent in c# can be a TRIANGLE[] or a List<TRIANGLE>()

edited Apr 09 '14 at 05:12

answered Jul 18 '12 at 12:39

Felice Pollano

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with a list you have to add and then you can use [] operator as an array. – Felice Pollano Jul 18 '12 at 13:53

score 1 · Answer 2 · answered Jul 18 '12 at 12:40

1

It looks like this function takes the GRID of voxels/cells and outputs the triangles. It is a pointer since you will get a list of triangles.

answered Jul 18 '12 at 12:40

Chefire

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Marching Cubes (C++ to C#)

2 Answers2