// return index of point in the middle of p1 and p2
private static int getMiddlePoint(int p1, int p2, ref List <Point3f> vertices, ref Dictionary <long, int> cache, float radius)
{
// first check if we have it already
bool firstIsSmaller = p1 < p2;
long smallerIndex = firstIsSmaller ? p1 : p2;
long greaterIndex = firstIsSmaller ? p2 : p1;
long key = (smallerIndex << 32) + greaterIndex;
int ret;
if (cache.TryGetValue(key, out ret))
{
return(ret);
}
// not in cache, calculate it
Point3f point1 = vertices[p1];
Point3f point2 = vertices[p2];
Point3f middle = new Point3f
(
(point1.X + point2.X) / 2f,
(point1.Y + point2.Y) / 2f,
(point1.Z + point2.Z) / 2f
);
// add vertex makes sure point is on unit sphere
int i = vertices.Count;
vertices.Add(middle.Unit() * radius);
// store it, return index
cache.Add(key, i);
return(i);
}