public override float ComputeMinimumRadius()
{
//Sample the shape in directions pointing to the vertices of a regular tetrahedron.
Vector3 a, b, c, d;
var direction = new Vector3(1, 1, 1);
GetLocalExtremePointWithoutMargin(ref direction, out a);
direction = new Vector3(-1, -1, 1);
GetLocalExtremePointWithoutMargin(ref direction, out b);
direction = new Vector3(-1, 1, -1);
GetLocalExtremePointWithoutMargin(ref direction, out c);
direction = new Vector3(1, -1, -1);
GetLocalExtremePointWithoutMargin(ref direction, out d);
Vector3 ab, cb, ac, ad, cd;
Vector3.Subtract(ref b, ref a, out ab);
Vector3.Subtract(ref b, ref c, out cb);
Vector3.Subtract(ref c, ref a, out ac);
Vector3.Subtract(ref d, ref a, out ad);
Vector3.Subtract(ref d, ref c, out cd);
//Find normals of triangles: ABC, CBD, ACD, ADB
Vector3 nABC, nCBD, nACD, nADB;
Vector3.Cross(ref ac, ref ab, out nABC);
Vector3.Cross(ref cd, ref cb, out nCBD);
Vector3.Cross(ref ad, ref ac, out nACD);
Vector3.Cross(ref ab, ref ad, out nADB);
//Find distances to planes.
float dABC, dCBD, dACD, dADB;
Vector3.Dot(ref a, ref nABC, out dABC);
Vector3.Dot(ref c, ref nCBD, out dCBD);
Vector3.Dot(ref a, ref nACD, out dACD);
Vector3.Dot(ref a, ref nADB, out dADB);
dABC /= nABC.Length();
dCBD /= nCBD.Length();
dACD /= nACD.Length();
dADB /= nADB.Length();
return collisionMargin + Math.Min(dABC, Math.Min(dCBD, Math.Min(dACD, dADB)));
}
