func (v Vec3) DistSqr(v1 Vec3) float32 {
	dx := v1[0] - v[0]
	dy := v1[1] - v[1]
	dz := v1[2] - v[2]
	return dx*dx + dy*dy + dz*dz
}
func (v Vec3) DistSqr(v1 Vec3) float32 {
	dx := v1[0] - v[0]
	dy := v1[1] - v[1]
	dz := v1[2] - v[2]
	return dx*dx + dy*dy + dz*dz
}
// DistSqr returns the square of the distance between two points.