From 957635b4841679ddf7cb385ad4186f84523994a0 Mon Sep 17 00:00:00 2001
From: fallenoak <git@fallenoak.me>
Date: Sun, 29 Nov 2020 23:17:09 -0600
Subject: [PATCH] feat(matrix): add C44Matrix::RotationAroundZ

---
 tempest/matrix/C44Matrix.cpp | 28 ++++++++++++++++++++++++
 tempest/matrix/C44Matrix.hpp |  3 +++
 test/Matrix.cpp              | 42 ++++++++++++++++++++++++++++++++++++
 3 files changed, 73 insertions(+)

diff --git a/tempest/matrix/C44Matrix.cpp b/tempest/matrix/C44Matrix.cpp
index 90b3419..548ea58 100644
--- a/tempest/matrix/C44Matrix.cpp
+++ b/tempest/matrix/C44Matrix.cpp
@@ -1,4 +1,32 @@
 #include "tempest/matrix/C44Matrix.hpp"
+#include <cmath>
+
+C44Matrix C44Matrix::RotationAroundZ(float angle) {
+    float cosAngle = cos(angle);
+    float sinAngle = sin(angle);
+
+    float a0 = cosAngle;
+    float a1 = sinAngle;
+    float a2 = 0.0f;
+    float a3 = 0.0f;
+
+    float b0 = -sinAngle;
+    float b1 = cosAngle;
+    float b2 = 0.0f;
+    float b3 = 0.0f;
+
+    float c0 = 0.0f;
+    float c1 = 0.0f;
+    float c2 = 1.0f;
+    float c3 = 0.0f;
+
+    float d0 = 0.0f;
+    float d1 = 0.0f;
+    float d2 = 0.0f;
+    float d3 = 1.0f;
+
+    return { a0, a1, a2, a3, b0, b1, b2, b3, c0, c1, c2, c3, d0, d1, d2, d3 };
+}
 
 C44Matrix C44Matrix::Adjoint() const {
     float a0 = this->b2 * this->c3 * this->d1 + this->b3 * this->c1 * this->d2 + this->b1 * this->c2 * this->d3 - this->b3 * this->c2 * this->d1 - this->b2 * this->c1 * this->d3 - this->b1 * this->c3 * this->d2;
diff --git a/tempest/matrix/C44Matrix.hpp b/tempest/matrix/C44Matrix.hpp
index 9283f66..2766115 100644
--- a/tempest/matrix/C44Matrix.hpp
+++ b/tempest/matrix/C44Matrix.hpp
@@ -3,6 +3,9 @@
 
 class C44Matrix {
     public:
+    // Static functions
+    static C44Matrix RotationAroundZ(float angle);
+
     // Member variables
     float a0 = 1.0f;
     float a1 = 0.0f;
diff --git a/test/Matrix.cpp b/test/Matrix.cpp
index 4193632..c2de9f0 100644
--- a/test/Matrix.cpp
+++ b/test/Matrix.cpp
@@ -1,6 +1,48 @@
 #include "tempest/Matrix.hpp"
 #include "test/Test.hpp"
 
+TEST_CASE("C44Matrix::RotationAroundZ", "[matrix]") {
+    SECTION("returns rotation matrix for 0 degree angle") {
+        auto rotation = C44Matrix::RotationAroundZ(0.0f);
+        CHECK(rotation.a0 == 1.0f);
+        CHECK(rotation.a1 == 0.0f);
+        CHECK(rotation.a2 == 0.0f);
+        CHECK(rotation.a3 == 0.0f);
+        CHECK(rotation.b0 == 0.0f);
+        CHECK(rotation.b1 == 1.0f);
+        CHECK(rotation.b2 == 0.0f);
+        CHECK(rotation.b3 == 0.0f);
+        CHECK(rotation.c0 == 0.0f);
+        CHECK(rotation.c1 == 0.0f);
+        CHECK(rotation.c2 == 1.0f);
+        CHECK(rotation.c3 == 0.0f);
+        CHECK(rotation.d0 == 0.0f);
+        CHECK(rotation.d1 == 0.0f);
+        CHECK(rotation.d2 == 0.0f);
+        CHECK(rotation.d3 == 1.0f);
+    }
+
+    SECTION("returns rotation matrix for 180 degree angle") {
+        auto rotation = C44Matrix::RotationAroundZ(3.1415927f);
+        CHECK(rotation.a0 == Approx(-1.0f).margin(0.0000001f));
+        CHECK(rotation.a1 == Approx(0.0f).margin(0.0000001f));
+        CHECK(rotation.a2 == 0.0f);
+        CHECK(rotation.a3 == 0.0f);
+        CHECK(rotation.b0 == Approx(0.0f).margin(0.0000001f));
+        CHECK(rotation.b1 == Approx(-1.0f).margin(0.0000001f));
+        CHECK(rotation.b2 == 0.0f);
+        CHECK(rotation.b3 == 0.0f);
+        CHECK(rotation.c0 == 0.0f);
+        CHECK(rotation.c1 == 0.0f);
+        CHECK(rotation.c2 == 1.0f);
+        CHECK(rotation.c3 == 0.0f);
+        CHECK(rotation.d0 == 0.0f);
+        CHECK(rotation.d1 == 0.0f);
+        CHECK(rotation.d2 == 0.0f);
+        CHECK(rotation.d3 == 1.0f);
+    }
+}
+
 TEST_CASE("C44Matrix", "[matrix]") {
     SECTION("constructs with default constructor") {
         C44Matrix matrix;