Implement the remaining operations and the projectile simulator

ray-tracer/Cargo.toml

@@ -6,3 +6,6 @@ edition = "2021"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
+
+[[bin]]
+name = "projectile"

ray-tracer/src/bin/projectile.rs

@@ -0,0 +1,37 @@
+use ray_tracer::types::*;
+
+#[derive(Clone, Copy)]
+struct Projectile {
+    position: Point,
+    velocity: Vector,
+}
+
+struct Environment {
+    gravity: Vector,
+    wind: Vector,
+}
+
+fn tick(env: &Environment, proj: &Projectile) -> Projectile {
+    let position = proj.position + proj.velocity;
+    let velocity = proj.velocity + env.gravity + env.wind;
+    Projectile { position, velocity }
+}
+
+fn main() {
+    let start = Projectile {
+        position: Point::new(0., 1., 0.),
+        velocity: Vector::new(1., 1., 0.).normalize() * 5.,
+    };
+
+    let e = Environment {
+        gravity: Vector::new(0., -0.1, 0.),
+        wind: Vector::new(-0.1, 0., 0.),
+    };
+
+    let mut p = start;
+    while p.position.y > 0. {
+        p = tick(&e, &p);
+    }
+
+    println!("distance travelled: [{}] {} {} {}", (p.position - start.position).magnitude(), p.position.x, p.position.y, p.position.z);
+}

ray-tracer/src/lib.rs

@@ -1,2 +1,2 @@
-mod types;
+pub mod types;
 

ray-tracer/src/types.rs

@@ -4,14 +4,20 @@ fn eq_f64(l: f64, r: f64) -> bool {
     (l - r).abs() < EPSILON
 }
 
-#[derive(Debug)]
+#[derive(Debug, Clone, Copy)]
-struct Tuple {
+pub struct Tuple {
-    x: f64,
+    pub x: f64,
-    y: f64,
+    pub y: f64,
-    z: f64,
+    pub z: f64,
-    w: f64, // Used for very low-level math. w = 1.0 indicates a point, w = 0.0 indicates a vector.
+    pub w: f64, // Used for very low-level math. w = 1.0 indicates a point, w = 0.0 indicates a vector.
-            // Theoretically the type system should make this redundant, so operations on points
+                // Theoretically the type system should make this redundant, so operations on points
-            // and vectors can always assert the correct value.
+                // and vectors can always assert the correct value.
+}
+
+impl Tuple {
+    fn dot(&self, r: &Tuple) -> f64 {
+        self.x * r.x + self.y * r.y + self.z * r.z + self.w * r.w
+    }
 }
 
 impl PartialEq for Tuple {
@@ -56,15 +62,46 @@ impl std::ops::Neg for Tuple {
     }
 }
 
-#[derive(Debug, PartialEq)]
+impl std::ops::Mul<f64> for Tuple {
-struct Point(Tuple);
+    type Output = Tuple;
+    fn mul(self, scalar: f64) -> Self::Output {
+        return Self::Output {
+            x: self.x * scalar,
+            y: self.y * scalar,
+            z: self.z * scalar,
+            w: self.w * scalar,
+        };
+    }
+}
+
+impl std::ops::Div<f64> for Tuple {
+    type Output = Tuple;
+    fn div(self, scalar: f64) -> Self::Output {
+        return Self::Output {
+            x: self.x / scalar,
+            y: self.y / scalar,
+            z: self.z / scalar,
+            w: self.w / scalar,
+        };
+    }
+}
+
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub struct Point(Tuple);
 
 impl Point {
-    fn new(x: f64, y: f64, z: f64) -> Self {
+    pub fn new(x: f64, y: f64, z: f64) -> Self {
         Self(Tuple { x, y, z, w: 1.0 })
     }
 }
 
+impl std::ops::Deref for Point {
+    type Target = Tuple;
+    fn deref(&self) -> &Tuple {
+        &self.0
+    }
+}
+
 impl From<Tuple> for Point {
     fn from(tuple: Tuple) -> Self {
         assert_eq!(tuple.w, 1.0);
@@ -108,13 +145,40 @@ impl std::ops::Neg for Point {
     }
 }
 
-#[derive(Debug, PartialEq)]
+#[derive(Clone, Copy, Debug, PartialEq)]
-struct Vector(Tuple);
+pub struct Vector(Tuple);
 
 impl Vector {
-    fn new(x: f64, y: f64, z: f64) -> Self {
+    pub fn new(x: f64, y: f64, z: f64) -> Self {
         Self(Tuple { x, y, z, w: 0.0 })
     }
+
+    pub fn magnitude(&self) -> f64 {
+        (self.x * self.x + self.y * self.y + self.z * self.z).sqrt()
+    }
+
+    pub fn normalize(&self) -> Self {
+        let mag = self.magnitude();
+        Self::new(self.x / mag, self.y / mag, self.z / mag)
+    }
+
+    pub fn dot(&self, r: &Vector) -> f64 {
+        self.0.dot(r)
+    }
+
+    pub fn cross(&self, r: &Vector) -> Self {
+        let x = self.y * r.z - self.z * r.y;
+        let y = self.z * r.x - self.x * r.z;
+        let z = self.x * r.y - self.y * r.x;
+        Self::new(x, y, z)
+    }
+}
+
+impl std::ops::Deref for Vector {
+    type Target = Tuple;
+    fn deref(&self) -> &Tuple {
+        &self.0
+    }
 }
 
 impl Default for Vector {
@@ -130,6 +194,13 @@ impl From<Tuple> for Vector {
     }
 }
 
+impl std::ops::Add for Vector {
+    type Output = Vector;
+    fn add(self, r: Self) -> Self {
+        Vector::from(self.0 + r.0)
+    }
+}
+
 impl std::ops::Sub for Vector {
     type Output = Vector;
     fn sub(self, r: Self) -> Self {
@@ -137,6 +208,14 @@ impl std::ops::Sub for Vector {
     }
 }
 
+impl std::ops::Mul<f64> for Vector {
+    type Output = Vector;
+    fn mul(self, r: f64) -> Self {
+        Vector::from(self.0 * r)
+    }
+}
+
+
 impl std::ops::Neg for Vector {
     type Output = Vector;
     fn neg(self) -> Self::Output {
@@ -253,4 +332,76 @@ mod tests {
             },
         );
     }
+
+    #[test]
+    fn multiply_tuple_by_scalar() {
+        assert_eq!(
+            Tuple {
+                x: 1.,
+                y: -2.,
+                z: 3.,
+                w: -4.
+            } * 3.5,
+            Tuple {
+                x: 3.5,
+                y: -7.,
+                z: 10.5,
+                w: -14.
+            }
+        );
+    }
+
+    #[test]
+    fn divide_tuple_by_scalar() {
+        assert_eq!(
+            Tuple {
+                x: 1.,
+                y: -2.,
+                z: 3.,
+                w: -4.
+            } / 2.,
+            Tuple {
+                x: 0.5,
+                y: -1.,
+                z: 1.5,
+                w: -2.
+            }
+        );
+    }
+
+    #[test]
+    fn magnitude_of_vector() {
+        assert_eq!(Vector::new(1., 0., 0.).magnitude(), 1.);
+        assert_eq!(Vector::new(0., 1., 0.).magnitude(), 1.);
+        assert_eq!(Vector::new(0., 0., 1.).magnitude(), 1.);
+        assert_eq!(Vector::new(1., 2., 3.).magnitude(), 14_f64.sqrt());
+        assert_eq!(Vector::new(-1., -2., -3.).magnitude(), 14_f64.sqrt());
+    }
+
+    #[test]
+    fn normalize_vector() {
+        assert_eq!(Vector::new(4., 0., 0.).normalize(), Vector::new(1., 0., 0.));
+        assert_eq!(
+            Vector::new(1., 2., 3.).normalize(),
+            Vector::new(0.26726, 0.53452, 0.80178)
+        );
+        assert_eq!(Vector::new(1., 2., 3.).normalize().magnitude(), 1.);
+    }
+
+    #[test]
+    fn dot_product() {
+        assert_eq!(Vector::new(1., 2., 3.).dot(&Vector::new(2., 3., 4.)), 20.);
+    }
+
+    #[test]
+    fn cross_product() {
+        assert_eq!(
+            Vector::new(1., 2., 3.).cross(&Vector::new(2., 3., 4.)),
+            Vector::new(-1., 2., -1.)
+        );
+        assert_eq!(
+            Vector::new(2., 3., 4.).cross(&Vector::new(1., 2., 3.)),
+            Vector::new(1., -2., 1.)
+        );
+    }
 }