func (v Vec2) DistSqr(v1 Vec2) float32 {
	dx := v1[0] - v[0]
	dy := v1[1] - v[1]
	return dx*dx + dy*dy
}
func (v Vec2) DistSqr(v1 Vec2) float32 {
	dx := v1[0] - v[0]
	dy := v1[1] - v[1]
	return dx*dx + dy*dy
}
// DistSqr returns the square of the distance between two points.