public Vec minus(Point p) { return new Vec(x-p.x, y-p.y, z-p.z); }
public Point plus(Vec v) { return new Point(x+v.x, y+v.y, z+v.z); }
+ public Point midpoint(Point p) { return new Point((x+p.x)/2, (y+p.y)/2, (z+p.z)/2); }
public void glVertex(GL gl) { gl.glVertex3f(x, y, z); }