From 5ca76b424a6bf27b3fafc3efa4cbeee6953eb244 Mon Sep 17 00:00:00 2001
From: Jon Janzen <jonjanzen@me.com>
Date: Sun, 28 Mar 2021 19:16:14 -0600
Subject: [PATCH] multiple matrix by tuple

---
 matrix/Cargo.toml  |  1 +
 matrix/src/lib.rs  | 83 ++++++++++++++++++++++++++++++++++++++++++++++
 structs/src/lib.rs |  4 +++
 3 files changed, 88 insertions(+)

diff --git a/matrix/Cargo.toml b/matrix/Cargo.toml
index 2f6e9d1..e9fa596 100644
--- a/matrix/Cargo.toml
+++ b/matrix/Cargo.toml
@@ -8,3 +8,4 @@ edition = "2018"
 
 [dependencies]
 approx = "0.4"
+structs = { path = "../structs" }
diff --git a/matrix/src/lib.rs b/matrix/src/lib.rs
index c5dfbc9..a559e63 100644
--- a/matrix/src/lib.rs
+++ b/matrix/src/lib.rs
@@ -1,6 +1,8 @@
 #[macro_use]
 extern crate approx;
 
+use structs::Tuple;
+
 use std::ops::Index;
 
 #[derive(Debug)]
@@ -28,6 +30,22 @@ impl Matrix {
             matrix: m,
         }
     }
+
+    pub fn new_empty(row_count: usize, col_count: usize) -> Matrix {
+        let mut rows = Vec::with_capacity(row_count);
+        for _ in 0..row_count {
+            let mut col = Vec::with_capacity(col_count);
+            for _ in 0..col_count {
+                col.push(0.0);
+            }
+            rows.push(col);
+        }
+        Matrix::new(rows)
+    }
+
+    pub fn new_empty_4() -> Matrix {
+        Matrix::new_empty(4, 4)
+    }
 }
 
 impl Index<usize> for Matrix {
@@ -57,6 +75,56 @@ impl PartialEq for Matrix {
     }
 }
 
+impl Matrix {
+    fn calc_val_for_mul(&self, row: usize, rhs: &Matrix, col: usize) -> f32 {
+        let mut sum = 0.0;
+        for i in 0..self.matrix.len() {
+            sum += self.matrix[row][i] * rhs.matrix[i][col];
+        }
+        sum
+    }
+
+    fn calc_val_for_mul_tuple(&self, row: usize, tuple: &Tuple) -> f32 {
+        (self.matrix[row][0] * tuple.x()) +
+        (self.matrix[row][1] * tuple.y()) +
+        (self.matrix[row][2] * tuple.z()) +
+        (self.matrix[row][3] * tuple.w())
+    }
+}
+
+impl std::ops::Mul<Matrix> for Matrix {
+    type Output = Matrix;
+
+    fn mul(self, _rhs: Matrix) -> Matrix {
+        let row_count = self.matrix.len();
+        let col_count = self.matrix[0].len();
+        let mut rows = Vec::with_capacity(row_count);
+        for row in 0..row_count {
+            let mut cols = Vec::with_capacity(col_count);
+            for col in 0..col_count {
+                cols.push(self.calc_val_for_mul(row, &_rhs, col));
+            }
+            rows.push(cols);
+        }
+        Matrix::new(rows)
+    }
+
+}
+
+impl std::ops::Mul<Tuple> for Matrix {
+    type Output = Tuple;
+
+    fn mul(self, _rhs: Tuple) -> Tuple {
+        Tuple::new(
+            self.calc_val_for_mul_tuple(0, &_rhs),
+            self.calc_val_for_mul_tuple(1, &_rhs),
+            self.calc_val_for_mul_tuple(2, &_rhs),
+            self.calc_val_for_mul_tuple(3, &_rhs),
+        )
+    }
+
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -194,4 +262,19 @@ mod tests {
 
         assert_eq!(matrix_a * matrix_b, expected);
     }
+
+    #[test]
+    fn multiply_by_tuple() {
+        let matrix = Matrix::from_array([
+            [1.0, 2.0, 3.0, 4.0],
+            [2.0, 4.0, 4.0, 2.0],
+            [8.0, 6.0, 4.0, 1.0],
+            [0.0, 0.0, 0.0, 1.0],
+        ]);
+
+        let tuple = Tuple::new(1.0, 2.0, 3.0, 1.0);
+        let expected = Tuple::new(18.0, 24.0, 33.0, 1.0);
+
+        assert_eq!(matrix * tuple, expected);
+    }
 }
diff --git a/structs/src/lib.rs b/structs/src/lib.rs
index 9e73153..420918d 100644
--- a/structs/src/lib.rs
+++ b/structs/src/lib.rs
@@ -55,6 +55,10 @@ impl Tuple {
         self.z
     }
 
+    pub fn w(&self) -> f32 {
+        self.w
+    }
+
     pub fn is_point(&self) -> bool {
         self.w == 1.0
     }