ft (wip): 10: dielectrics

src/vec3.rs

@@ -101,8 +101,18 @@ impl Vec3 {
             && default().is_close(self.b, 0.)
     }
 
-    pub fn reflect(&self, o: &Vec3) -> Vec3 {
-        *self - 2. * self.dot(o) * o
+    pub fn reflect(&self, n: &Self) -> Self {
+        *self - 2. * self.dot(n) * n
+    }
+
+    pub fn refract(&self, n: &Self, etai_over_etat: f32) -> Self {
+        let mut cos_theta = -self.dot(n);
+        cos_theta = if cos_theta > 1.0 { 1.0 } else { cos_theta };
+
+        let r_out_perp = etai_over_etat * (*self + cos_theta * n);
+        let r_out_parr = -sqrt((1. - r_out_perp.length_squared()).abs()) * n;
+
+        return r_out_perp + r_out_parr;
     }
 
     pub fn output(self) -> image::Rgb<u8> {
@@ -139,6 +149,14 @@ impl Vec3 {
     }
 }
 
+impl Neg for &Vec3 {
+    type Output = Vec3;
+
+    fn neg(self) -> Self::Output {
+        -*self
+    }
+}
+
 impl Neg for Vec3 {
     type Output = Self;