Implement 4x4 * 4x1

rtchallenge/src/matrices.rs

@@ -1,6 +1,8 @@
 use std::fmt;
 use std::ops::{Add, Div, Index, Mul, Neg, Sub};
 
+use crate::tuples::Tuple;
+
 #[derive(Default, Clone, Copy)]
 /// Matrix4x4 represents a 4x4 matrix in row-major form. So, element `m[i][j]` corresponds to m<sub>i,j</sub>
 /// where `i` is the row number and `j` is the column number.
@@ -246,6 +248,37 @@ impl Mul<Matrix4x4> for Matrix4x4 {
     }
 }
 
+impl Mul<Tuple> for Matrix4x4 {
+    type Output = Tuple;
+
+    /// Implement matrix multiplication for `Matrix4x4` * `Tuple`.
+    ///
+    /// # Examples
+    /// ```
+    /// use rtchallenge::matrices::Matrix4x4;
+    /// use rtchallenge::tuples::Tuple;
+    ///
+    /// let a = Matrix4x4::new(
+    ///     [1., 2., 3., 4.],
+    ///     [2., 4., 4., 2.],
+    ///     [8., 6., 4., 1.],
+    ///     [0., 0., 0., 1.],
+    /// );
+    /// let b = Tuple::new(1.,2.,3.,1.);
+    ///
+    /// assert_eq!(a * b, Tuple::new(18., 24., 33., 1.));
+    /// ```
+    fn mul(self, t: Tuple) -> Tuple {
+        let m = self;
+        Tuple {
+            x: m.m[0][0] * t.x + m.m[0][1] * t.y + m.m[0][2] * t.z + m.m[0][3] * t.w,
+            y: m.m[1][0] * t.x + m.m[1][1] * t.y + m.m[1][2] * t.z + m.m[1][3] * t.w,
+            z: m.m[2][0] * t.x + m.m[2][1] * t.y + m.m[2][2] * t.z + m.m[2][3] * t.w,
+            w: m.m[3][0] * t.x + m.m[3][1] * t.y + m.m[3][2] * t.z + m.m[3][3] * t.w,
+        }
+    }
+}
+
 impl PartialEq for Matrix4x4 {
     fn eq(&self, rhs: &Matrix4x4) -> bool {
         let l = self.m;