int[] AdjacencyCount(Mesh mesh)
{
int i;
int node;
int n1, n2, n3;
int tri_id;
int neigh_id;
int[] adj_rows = new int[node_num + 1];
// Set every node to be adjacent to itself.
for (node = 0; node < node_num; node++)
{
adj_rows[node] = 1;
}
// Examine each triangle.
foreach (var tri in mesh.triangles.Values)
{
tri_id = tri.id;
n1 = tri.vertices[0].id;
n2 = tri.vertices[1].id;
n3 = tri.vertices[2].id;
// Add edge (1,2) if this is the first occurrence, that is, if
// the edge (1,2) is on a boundary (nid <= 0) or if this triangle
// is the first of the pair in which the edge occurs (tid < nid).
neigh_id = tri.neighbors[2].triangle.id;
if (neigh_id < 0 || tri_id < neigh_id)
{
adj_rows[n1] += 1;
adj_rows[n2] += 1;
}
// Add edge (2,3).
neigh_id = tri.neighbors[0].triangle.id;
if (neigh_id < 0 || tri_id < neigh_id)
{
adj_rows[n2] += 1;
adj_rows[n3] += 1;
}
// Add edge (3,1).
neigh_id = tri.neighbors[1].triangle.id;
if (neigh_id < 0 || tri_id < neigh_id)
{
adj_rows[n3] += 1;
adj_rows[n1] += 1;
}
}
// We used ADJ_COL to count the number of entries in each column.
// Convert it to pointers into the ADJ array.
for (node = node_num; 1 <= node; node--)
{
adj_rows[node] = adj_rows[node - 1];
}
adj_rows[0] = 1;
for (i = 1; i <= node_num; i++)
{
adj_rows[i] = adj_rows[i - 1] + adj_rows[i];
}
return adj_rows;
}
