geom-demo/geom/demos/reflection.py

import pygame
from ..geom import Polygon, generate_polygon
from .. import WIDTH, HEIGHT, get_cursor_pos, get_inputs
from ..colors import *
from ..math import *
from ..draw import *
from math import pi, sin, cos

class Reflection:

    title = "Reflection"

    def __init__(self):
        self.s_angle = -pi/8

    def handle_key_down(self, key):
        pass

    def handle_input(self):
        inputs = get_inputs()
        if inputs[pygame.K_q]:
            self.s_angle -= (1/60) * pi/3
        if inputs[pygame.K_e]:
            self.s_angle += (1/60) * pi/3

    def render(self, surface):
        self.handle_input()

        s_end = scale(cos(self.s_angle),
                      sin(self.s_angle),
                      WIDTH)
        s_start = reverse(*s_end)

        # the reflecting surface
        s = sub(*s_end, *s_start)

        # the incoming ray, towards reflection surface
        # it's important that it is pointing towards the reflecting surface
        incoming = sub(0, 0, *get_cursor_pos())

        # surface normal
        normal = normalize(*lnormal(*s))

        # projection of incoming ray onto normal, multiplied by 2
        projection_2 = dot(*incoming, *normal) * 2

        # outgoing ray, away from reflection surface
        outgoing = sub(*incoming, *scale(*normal, projection_2))

        line(surface, WHITE, s_start, s_end)
        line(surface, CYAN, (0, 0), scale(*normal, 1000))
        line(surface, YELLOW, get_cursor_pos(), (0, 0))
        line(surface, RED, (0, 0), outgoing)