Support for 2D transformations in addition to 3D in Matrix classes.

src/Math/Matrix3.h

@@ -24,9 +24,56 @@
 
 namespace Magnum { namespace Math {
 
-/** @brief 3x3 matrix */
+/**
+@brief 3x3 matrix
+
+Provides functions for transformations in 2D. See also Matrix4 for 3D
+transformations.
+*/
 template<class T> class Matrix3: public Matrix<3, T> {
     public:
+        /**
+         * @brief 2D translation matrix
+         * @param vec   Translation vector
+         *
+         * @see Matrix4::translation()
+         */
+        inline constexpr static Matrix3<T> translation(const Vector2<T>& vec) {
+            return Matrix3<T>( /* Column-major! */
+                T(1), T(0), T(0),
+                T(0), T(1), T(0),
+                vec.x(), vec.y(), T(1)
+            );
+        }
+
+        /**
+         * @brief 2D scaling matrix
+         * @param vec   Scaling vector
+         *
+         * @see Matrix4::scaling()
+         */
+        inline constexpr static Matrix3<T> scaling(const Vector2<T>& vec) {
+            return Matrix3<T>( /* Column-major! */
+                vec.x(), T(0), T(0),
+                T(0), vec.y(), T(0),
+                T(0), T(0), T(1)
+            );
+        }
+
+        /**
+         * @brief 3D rotation matrix
+         * @param angle Rotation angle (counterclockwise, in radians)
+         *
+         * @see Matrix4::rotation()
+         */
+        static Matrix3<T> rotation(T angle) {
+            return Matrix3<T>( /* Column-major! */
+                T(cos(angle)), T(sin(angle)), T(0),
+                -T(sin(angle)), T(cos(angle)), T(0),
+                T(0), T(0), T(1)
+            );
+        }
+
         /** @copydoc Matrix::Matrix(ZeroType) */
         inline constexpr explicit Matrix3(typename Matrix<3, T>::ZeroType): Matrix<3, T>(Matrix<3, T>::Zero) {}
 

src/Math/Matrix4.h

@@ -27,14 +27,18 @@ namespace Magnum { namespace Math {
 /**
 @brief 4x4 matrix
 
+Provides functions for transformations in 3D. See also Matrix3 for 2D
+transformations.
 @todo Shearing
 @todo Reflection
  */
 template<class T> class Matrix4: public Matrix<4, T> {
     public:
         /**
-         * @brief Translation matrix
+         * @brief 3D translation matrix
          * @param vec   Translation vector
+         *
+         * @see Matrix3::translation()
          */
         inline constexpr static Matrix4<T> translation(const Vector3<T>& vec) {
             return Matrix4<T>( /* Column-major! */
@@ -46,8 +50,10 @@ template<class T> class Matrix4: public Matrix<4, T> {
         }
 
         /**
-         * @brief Scaling matrix
+         * @brief 3D scaling matrix
          * @param vec   Scaling vector
+         *
+         * @see Matrix3::scaling()
          */
         inline constexpr static Matrix4<T> scaling(const Vector3<T>& vec) {
             return Matrix4<T>( /* Column-major! */
@@ -59,10 +65,11 @@ template<class T> class Matrix4: public Matrix<4, T> {
         }
 
         /**
-         * @brief Rotation matrix
+         * @brief 3D rotation matrix
          * @param angle Rotation angle (counterclockwise, in radians)
          * @param vec   Rotation vector
          *
+         * @see Matrix3::rotation()
          * @todo optimize - Assume the vectors are normalized?
          */
         static Matrix4<T> rotation(T angle, const Vector3<T>& vec) {

src/Math/Test/Matrix3Test.cpp

@@ -19,6 +19,7 @@
 #include <QtTest/QTest>
 
 #include "Matrix3.h"
+#include "Math.h"
 
 QTEST_APPLESS_MAIN(Magnum::Math::Test::Matrix3Test)
 
@@ -51,6 +52,36 @@ void Matrix3Test::constructIdentity() {
     QVERIFY(identity3 == identity3Expected);
 }
 
+void Matrix3Test::translation() {
+    Matrix3 matrix(
+        1.0f, 0.0f, 0.0f,
+        0.0f, 1.0f, 0.0f,
+        3.0f, 1.0f, 1.0f
+    );
+
+    QVERIFY(Matrix3::translation({3.0f, 1.0f}) == matrix);
+}
+
+void Matrix3Test::scaling() {
+    Matrix3 matrix(
+        3.0f, 0.0f, 0.0f,
+        0.0f, 1.5f, 0.0f,
+        0.0f, 0.0f, 1.0f
+    );
+
+    QVERIFY(Matrix3::scaling({3.0f, 1.5f}) == matrix);
+}
+
+void Matrix3Test::rotation() {
+    Matrix3 matrix(
+        0.965926f, 0.258819f, 0.0f,
+        -0.258819f, 0.965926f, 0.0f,
+        0.0f, 0.0f, 1.0f
+    );
+
+    QVERIFY(Matrix3::rotation(deg(15.0f)) == matrix);
+}
+
 void Matrix3Test::debug() {
     Matrix3 m(
         3.0f, 5.0f, 8.0f,

src/Math/Test/Matrix3Test.h

@@ -25,6 +25,9 @@ class Matrix3Test: public QObject {
     private slots:
         void constructIdentity();
 
+        void translation();
+        void scaling();
+        void rotation();
         void debug();
 };