From 2c1b5354fa68f4b3d3f1a7205e6ecaaa1a8f04c9 Mon Sep 17 00:00:00 2001
From: Jon Janzen <jonjanzen@me.com>
Date: Fri, 3 Sep 2021 20:17:18 -0600
Subject: [PATCH] rotation complete

---
 features/src/transformations.rs | 38 +++++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)

diff --git a/features/src/transformations.rs b/features/src/transformations.rs
index ce43d6e..9fb1bef 100644
--- a/features/src/transformations.rs
+++ b/features/src/transformations.rs
@@ -30,6 +30,24 @@ impl Matrix {
             [0.0, 0.0, 0.0, 1.0],
         ])
     }
+
+    pub fn rotation_y(r: f32) -> Self {
+        Matrix::from_array([
+            [r.cos(), 0.0, r.sin(), 0.0],
+            [0.0, 1.0, 0.0, 0.0],
+            [-1.0 * r.sin(), 0.0,  r.cos() , 0.0],
+            [0.0, 0.0, 0.0, 1.0],
+        ])
+    }
+
+    pub fn rotation_z(r: f32) -> Self {
+        Matrix::from_array([
+            [r.cos(), -1.0 * r.sin(), 0.0, 0.0],
+            [r.sin(), r.cos(), 0.0, 0.0],
+            [0.0, 0.0, 1.0, 0.0],
+            [0.0, 0.0, 0.0, 1.0],
+        ])
+    }
 }
 
 #[cfg(test)]
@@ -119,4 +137,24 @@ mod tests {
 
         assert_eq!(&inv * &p, Tuple::point(0.0, sqrt_of_2() / 2.0, -1.0 * sqrt_of_2() / 2.0));
     }
+
+    #[test]
+    fn rotating_point_around_y_axis() {
+        let p = Tuple::point(0.0, 0.0, 1.0);
+        let half_quarter = Matrix::rotation_y(PI / 4.0);
+        let full_quarter = Matrix::rotation_y(PI / 2.0);
+
+        assert_eq!(&half_quarter * &p, Tuple::point(sqrt_of_2() / 2.0, 0.0, sqrt_of_2() / 2.0));
+        assert_eq!(&full_quarter * &p, Tuple::point(1.0, 0.0, 0.0));
+    }
+
+    #[test]
+    fn rotating_point_around_z_axis() {
+        let p = Tuple::point(0.0, 1.0, 0.0);
+        let half_quarter = Matrix::rotation_z(PI / 4.0);
+        let full_quarter = Matrix::rotation_z(PI / 2.0);
+
+        assert_eq!(&half_quarter * &p, Tuple::point(-1.0 * sqrt_of_2() / 2.0, sqrt_of_2() / 2.0, 0.0));
+        assert_eq!(&full_quarter * &p, Tuple::point(-1.0, 0.0, 0.0));
+    }
 }