ft: 5,6.1: sphere class + normals

src/vec3.rs

@@ -46,15 +46,11 @@ impl Vec3 {
         (self.r * self.r + self.g * self.g + self.b * self.b) as f32
     }
 
-    pub fn dot(self, other: Vec3) -> Vec3 {
-        Vec3 {
-            r: self.r * other.r,
-            g: self.g * other.g,
-            b: self.b * other.b,
-        }
+    pub fn dot(&self, other: &Vec3) -> f32 {
+        self.r * other.r + self.g * other.g + self.b * other.b
     }
 
-    pub fn cross(self, other: Vec3) -> Vec3 {
+    pub fn cross(&self, other: &Vec3) -> Vec3 {
         Vec3 {
             r: self.g * other.b - self.b * other.g,
             g: self.b * other.r - self.r * other.b,
@@ -142,6 +138,17 @@ impl AddAssign<f32> for Vec3 {
         };
     }
 }
+impl Sub<&Vec3> for Vec3 {
+    type Output = Self;
+
+    fn sub(self, rhs: &Self) -> Self {
+        Self {
+            r: self.r - rhs.r,
+            g: self.g - rhs.g,
+            b: self.b - rhs.b,
+        }
+    }
+}
 
 impl Sub<Vec3> for Vec3 {
     type Output = Self;