Fix refract3 method

examples/19_refraction.py

@@ -0,0 +1,46 @@
+from pyrt.geometry.vertex import Vertex
+from pyrt import material
+from pyrt.math import Vec3
+from pyrt.scene import Scene
+from pyrt.light import PointLight
+from pyrt.geometry import Sphere, Triangle
+from pyrt.material import PhongMaterial
+from pyrt.camera import PerspectiveCamera
+from pyrt.renderer import SimpleRT
+from PIL import Image
+
+width = 400
+height = 300
+
+camera = PerspectiveCamera(width, height, 60)
+camera.setView(Vec3(0,-10,0), Vec3(0,0,0), Vec3(0,0,1))
+
+scene = Scene()
+scene.addLight(PointLight(Vec3(-1,-8,1)))
+
+# Triangle behind lens
+A = Vertex(position=(-1.5, 6, 0))
+B = Vertex(position=(3.5, 6, 0))
+C = Vertex(position=(1, 6, 5.))
+scene.add(Triangle(A, B, C, material=PhongMaterial(color=Vec3(1,1,1))))
+
+# Floor
+A = Vertex(position=(-5.0, -5.0, -2.0))
+B = Vertex(position=( 5.0, -5.0, -2.0))
+C = Vertex(position=( 5.0,  5.0, -2.0))
+D = Vertex(position=(-5.0,  5.0, -2.0))
+
+floormaterial = PhongMaterial(color=Vec3(.2,.2,.2)  )
+scene.add(Triangle(A,B,C, material=floormaterial))
+scene.add(Triangle(A,C,D, material=floormaterial))
+
+# Two lenses
+scene.add(Sphere(Vec3(-1, 5.7, -1), 2.5, PhongMaterial(color=Vec3(.9, .9, .9),
+    transparency=.8, refraction=1.5)))
+scene.add(Sphere(Vec3(2.8, 5, .5), 1.8, PhongMaterial(color=Vec3(.9, .9, .9),
+    transparency=.8, refraction=1.5)))
+
+scene.setCamera(camera)
+engine = SimpleRT(iterations=4, shadow=True)
+image = engine.render(scene)
+image.save("16.png")

pyrt/math/constants.py

@@ -5,3 +5,4 @@
 """
 
 G_EPSILON = 1E-11
+G_REFRACTION_EPSILON = 1E-4

pyrt/math/vecops.py

@@ -103,13 +103,15 @@ def refract3(N, I, eta):
     I: Incident vector
     eta: Refraction koefficient
     """
-    d = dot3(I, N)
+    d = dot3(N, I)
+    if d > 0:
+        return refract3(I, N * -1, 1 / eta)
+    eta = 1 / eta
     k = 1 - eta * eta * (1 - d * d)
     if k < 0:
         return I
     else:
         return I * eta - N * (eta * d + math.sqrt(k))
-
 
 # ---------------------------------------------------------------------------------------------------------------------
 

pyrt/renderer/simplert.py

@@ -91,7 +91,7 @@ def _recurse_shade(self, scene: Scene, ray: Ray, iteration_num: int) -> tuple:
 
         if hitrecord.material.transparency > G_EPSILON:
             refract_ray = Ray(
-                hitrecord.point + normalize3(ray.direction) * G_EPSILON, 
+                hitrecord.point + ray.direction * G_REFRACTION_EPSILON, 
                 refract3(normalize3(hitrecord.normal_g), normalize3(ray.direction), hitrecord.material.refraction)
             )
             new_r, new_g, new_b = self._recurse_shade(scene, refract_ray, iteration_num - 1)