Add missing file that should have been in earlier commit

src/integrators.rs

@@ -0,0 +1,26 @@
+use nalgebra::{RealField, Vector3};
+
+use super::raycasting::IntersectionInfo;
+
+pub trait Integrator<T: RealField> {
+    fn integrate(&self, info: &IntersectionInfo<T>) -> T;
+}
+
+pub struct DirectionalLight<T: RealField> {
+    pub direction: Vector3<T>,
+    pub intensity: T,
+}
+
+pub struct PhongIntegrator<T: RealField> {
+    pub ambient_light: T,
+    pub lights: Vec<DirectionalLight<T>>,
+}
+
+impl<T: RealField> Integrator<T> for PhongIntegrator<T> {
+    fn integrate(&self, info: &IntersectionInfo<T>) -> T {
+        self.lights
+            .iter()
+            .map(|light| light.intensity * light.direction.dot(&info.normal))
+            .fold(self.ambient_light, |a, b| a + b)
+    }
+}