Math: converting complex number to rotation matrix.

src/Math/Complex.h

@@ -23,10 +23,7 @@
 #include <Utility/Assert.h>
 #include <Utility/Debug.h>
 
-#include "Math/Angle.h"
-#include "Math/MathTypeTraits.h"
-
-#include "magnumVisibility.h"
+#include "Math/Matrix.h"
 
 namespace Magnum { namespace Math {
 
@@ -125,6 +122,22 @@ template<class T> class Complex {
             return Rad<T>(std::atan2(_imaginary, _real));
         }
 
+        /**
+         * @brief Convert complex number to rotation matrix
+         *
+         * @f[
+         *      M = \begin{pmatrix}
+         *               a & -b \\
+         *               b &  a
+         *          \end{pmatrix}
+         * @f]
+         * @see Matrix3::from(const Matrix<2, T>&, const Vector2<T>&)
+         */
+        Matrix<2, T> matrix() const {
+            return {Vector<2, T>(_real, _imaginary),
+                    Vector<2, T>(-_imaginary, _real)};
+        }
+
         /**
          * @brief Add complex number and assign
          *

src/Math/Test/ComplexTest.cpp

@@ -17,7 +17,7 @@
 #include <TestSuite/Tester.h>
 
 #include "Math/Complex.h"
-#include "Math/Vector2.h"
+#include "Math/Matrix3.h"
 
 namespace Magnum { namespace Math { namespace Test {
 
@@ -47,6 +47,7 @@ class ComplexTest: public Corrade::TestSuite::Tester {
 
         void angle();
         void rotation();
+        void matrix();
 
         void debug();
 };
@@ -74,6 +75,7 @@ ComplexTest::ComplexTest() {
 
              &ComplexTest::angle,
              &ComplexTest::rotation,
+             &ComplexTest::matrix,
 
              &ComplexTest::debug);
 }
@@ -82,6 +84,8 @@ typedef Math::Deg<float> Deg;
 typedef Math::Rad<float> Rad;
 typedef Math::Complex<float> Complex;
 typedef Math::Vector2<float> Vector2;
+typedef Math::Matrix3<float> Matrix3;
+typedef Math::Matrix<2, float> Matrix2;
 
 void ComplexTest::construct() {
     Complex c(0.5f, -3.7f);
@@ -245,6 +249,13 @@ void ComplexTest::rotation() {
     CORRADE_COMPARE_AS(Complex().rotationAngle(), Deg(0.0f), Rad);
 }
 
+void ComplexTest::matrix() {
+    Complex a = Complex::rotation(Deg(37.0f));
+    Matrix2 m = Matrix3::rotation(Deg(37.0f)).rotationScaling();
+
+    CORRADE_COMPARE(a.matrix(), m);
+}
+
 void ComplexTest::debug() {
     std::ostringstream o;