From be2d23914d0b41ba6b2f264897ac543b0c5c691b Mon Sep 17 00:00:00 2001
From: Jon Janzen <jonjanzen@me.com>
Date: Fri, 3 Sep 2021 19:13:26 -0600
Subject: [PATCH] transformation function

---
 features/src/matrix.rs          |  2 +-
 features/src/transformations.rs | 46 +++++++++++++++++++++++++++++++--
 features/src/tuples.rs          |  4 ++-
 3 files changed, 48 insertions(+), 4 deletions(-)

diff --git a/features/src/matrix.rs b/features/src/matrix.rs
index 2c488e9..58626a9 100644
--- a/features/src/matrix.rs
+++ b/features/src/matrix.rs
@@ -534,7 +534,7 @@ mod tests {
 
     }
 
-    fn assert_matrix_eq(_lhs: &Matrix, _rhs: &Matrix, max_relative: f32) -> bool {
+    pub fn assert_matrix_eq(_lhs: &Matrix, _rhs: &Matrix, max_relative: f32) -> bool {
         if _lhs.matrix.len() != _rhs.matrix.len() {
             return false;
         }
diff --git a/features/src/transformations.rs b/features/src/transformations.rs
index d3126d3..316c0d3 100644
--- a/features/src/transformations.rs
+++ b/features/src/transformations.rs
@@ -1,8 +1,50 @@
+use crate::matrix::Matrix;
+use crate::structs::Tuple;
+
+
+impl Matrix {
+    pub fn translation(x: f32, y: f32, z: f32) -> Self {
+        Matrix::from_array([
+            [1.0, 0.0, 0.0, x],
+            [0.0, 1.0, 0.0, y],
+            [0.0, 0.0, 1.0, z],
+            [0.0, 0.0, 0.0, 1.0],
+        ])
+    }
+}
 
 #[cfg(test)]
 mod tests {
+    use super::*;
+
     #[test]
-    fn it_works() {
-        assert_eq!(2 + 2, 4);
+    fn multiply_by_a_translations_matrix() {
+        let transform = Matrix::translation(5.0, -3.0, 2.0);
+        let p = Tuple::point(-3.0, 4.0, 5.0);
+        
+
+        let expected_point = Tuple::point(2.0, 1.0, 7.0);
+
+        let translated_point = &transform * &p;
+
+        assert_eq!(expected_point, translated_point);
+    }
+
+    #[test]
+    fn multiply_by_the_inverse_of_a_translation_matrix() {
+        let transform = Matrix::translation(5.0, -3.0, 2.0);
+        let inv = transform.inverse();
+        let p = Tuple::point(-3.0, 4.0, 5.0);
+
+        let expected_point = Tuple::point(-8.0, 7.0, 3.0);
+        assert_eq!(&inv * &p, expected_point);
+    }
+
+    #[test]
+    fn translation_does_not_affect_vectors() {
+        let transform = Matrix::translation(5.0, -3.0, 2.0);
+        let v = Tuple::vector(-3.0, 4.0, 5.0);
+
+        assert_eq!(&transform * &v, v);
     }
 }
diff --git a/features/src/tuples.rs b/features/src/tuples.rs
index 1dea01a..b1dd0bb 100644
--- a/features/src/tuples.rs
+++ b/features/src/tuples.rs
@@ -104,7 +104,7 @@ fn cross(lhs: PointVector, rhs: PointVector) -> PointVector {
 }
 
 #[cfg(test)]
-mod tests {
+pub mod tests {
     use super::*;
 
     #[test]
@@ -318,4 +318,6 @@ mod tests {
         assert_eq!(b_cross_a, cross(b, a));
 
     }
+
+    pub fn 
 }