Add reflection demo

geom/demos/reflection.py

@@ -0,0 +1,52 @@
+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/4
+
+    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
+        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)

geom/screen.py

@@ -1,5 +1,5 @@
 import pygame
-from .demos import aabb, vec_proj, sat
+from .demos import aabb, vec_proj, sat, reflection
 from . import HEIGHT
 from .colors import *
 from .draw import text_screen
@@ -9,6 +9,7 @@ class Screen:
     def __init__(self):
         self.demos = [
             vec_proj.VecProj(),
+            reflection.Reflection(),
             aabb.AABBDistance(),
             aabb.PointAABBDistance(),
             sat.SeparatingAxisTheorem(),