void Mesh::ScaleZ(float s)
{
	Vector c = ComputeCentroid();
	Triangle *tri = tris;
	for(int i = 0; i < numTris; i++, tri++)
	{
		tri->ScaleZAboutPoint(s, c);
	}
}
void Mesh::ScaleZAboutPoint(float s, Vector point)
{
	Triangle *tri = tris;
	for(int i = 0; i < numTris; i++, tri++)
	{
		tri->ScaleZAboutPoint(s, point);
	}
	centroidChanged = true;
}