Add normal mapping with example

examples/18_normal_mapping.py

@@ -0,0 +1,46 @@
+# Example 16: Normal mappings
+#
+# Two spheres are rendered, one with normal map and the other without it
+
+from pyrt.math import Vec3
+from pyrt.scene import Scene
+from pyrt.light import PointLight
+from pyrt.geometry import Triangle, Sphere, Vertex
+from pyrt.material import NormalMappedMaterial, TextureMaterial
+from pyrt.camera import PerspectiveCamera
+from pyrt.renderer import SimpleRT
+from PIL import Image
+
+# Specify width/height
+width = 400
+height = 300
+
+# now create a camera and a view like in example 5:
+camera = PerspectiveCamera(width, height, 60)
+camera.setView(Vec3(0,-10,0), Vec3(0,0,0), Vec3(0,0,1))
+
+# Create a scene
+scene = Scene()
+
+# Add a light to the scene
+scene.addLight(PointLight(Vec3(0,0,0)))
+
+# Create material with normal mappings
+material0 = NormalMappedMaterial(texturepath='tex16.png', normalmappath='normalmap.png')
+material1 = TextureMaterial(texturepath='tex16.png')
+
+# Add a sphere to the scene:
+scene.add(Sphere(center=Vec3(-3.5,0.,0.), radius=2.8, material=material0))
+scene.add(Sphere(center=Vec3(3.5,0.,0.), radius=2.8, material=material1))
+
+# Now tell the scene which camera we use
+scene.setCamera(camera)
+
+# Create a raytracer using "SimpleRT"
+engine = SimpleRT()
+
+# Render the scene:
+image = engine.render(scene)
+
+# Save the resulting image using pillow
+image.save("18.png")

pyrt/material/__init__.py

@@ -5,4 +5,6 @@
 """
 
 from .material import Material
-from .phongmaterial import PhongMaterial
+from .phongmaterial import PhongMaterial
+from .texturematerial import TextureMaterial
+from .normalmappedmaterial import NormalMappedMaterial

pyrt/material/normalmappedmaterial.py

@@ -0,0 +1,23 @@
+from .texture import Texture
+from .texturematerial import TextureMaterial
+from ..math import Vec3, Ray, HitRecord, dot3, reflect3, normalize3, clamp3
+from ..camera import Camera
+
+
+class NormalMappedMaterial(TextureMaterial):
+    """Texture Material Class"""
+
+    def __init__(self, color: Vec3 = Vec3(1., 1., 1.), shininess: float = 10.0, reflectivity: float = 0.0,
+                 refraction: float = 1.0, texturepath: str = '', normalmappath: str = ''):
+        TextureMaterial.__init__(self, color, shininess, reflectivity, refraction, texturepath)
+        self.normalmap = None if len(normalmappath) == 0 else Texture(normalmappath)
+
+    def shade(self, camera: Camera, ray: Ray, hitrecord: HitRecord, lights: list) -> Vec3:
+        """
+        Shade method: Texture
+
+        texture shader
+        """
+        diff = 2 * (self.normalmap.color(hitrecord.texcoord) - Vec3(0.5, 0.5, 0.5))
+        hitrecord.normal_g = normalize3(diff)
+        return super().shade(camera, ray, hitrecord, lights)