// Given a reference to a GridCell and an isolevel, calculate the
// triangulation representing the intersection of the GridCell and the
// isosurface
public static void Triangulate(ref GridCell cell, float isolevel)
{
// Clear any calculations made in the GridCell
cell.Clear();
// Index into tables representing configuration number of GridCell
int index = 0;
// Calculate configuration number by determining which vertices are
// below the isosurface
//
// Note: The "|=" operator sets the bit at the index given,
// essentially adding that value to the index if it not already set
for (int i = 0; i < 8; i++)
{
if (cell.p[i].Value < isolevel)
{
index |= 1 << i;
}
}
// Return if the GridCell does not intersect the isosurface at all
if (edgeTable[index] == 0)
{
return;
}
// Calculate interpolated edge position for each edge in the GridCell
//
// Note: The expression "edgeTable[index] & (1 << position)) != 0"
// returns true if the bit at the given position is set
for (int i = 0; i < 12; i++)
{
if ((edgeTable[index] & (1 << i)) != 0)
{
cell.edgepoints[i] = Interpolate(cell.p[vertexTable[i, 0]], cell.p[vertexTable[i, 1]], isolevel);
}
}
// Determine triangles for GridCell configuration
for (int i = 0; triangleTable[index, i] != -1; i += 3)
{
cell.triangles[cell.numTriangles].p[0]
= cell.edgepoints[triangleTable[index, i]];
cell.triangles[cell.numTriangles].p[1]
= cell.edgepoints[triangleTable[index, i + 1]];
cell.triangles[cell.numTriangles].p[2]
= cell.edgepoints[triangleTable[index, i + 2]];
cell.numTriangles++;
}
}
