Math: Added Vector2::cross().

src/Math/Test/Vector2Test.cpp

@@ -26,7 +26,7 @@
 #include <TestSuite/Tester.h>
 #include <Utility/Configuration.h>
 
-#include "Math/Vector2.h"
+#include "Math/Vector3.h"
 
 struct Vec2 {
     float x, y;
@@ -63,6 +63,7 @@ class Vector2Test: public Corrade::TestSuite::Tester {
         void convert();
 
         void access();
+        void cross();
         void axes();
         void scales();
 
@@ -70,6 +71,7 @@ class Vector2Test: public Corrade::TestSuite::Tester {
         void configuration();
 };
 
+typedef Math::Vector3<Int> Vector3i;
 typedef Math::Vector2<Float> Vector2;
 typedef Math::Vector2<Int> Vector2i;
 
@@ -83,6 +85,7 @@ Vector2Test::Vector2Test() {
               &Vector2Test::convert,
 
               &Vector2Test::access,
+              &Vector2Test::cross,
               &Vector2Test::axes,
               &Vector2Test::scales,
 
@@ -162,6 +165,14 @@ void Vector2Test::access() {
     CORRADE_COMPARE(y, -2.0f);
 }
 
+void Vector2Test::cross() {
+    Vector2i a(1, -1);
+    Vector2i b(4, 3);
+
+    CORRADE_COMPARE(Vector2i::cross(a, b), 7);
+    CORRADE_COMPARE(Vector3i::cross({a, 0}, {b, 0}), Vector3i(0, 0, Vector2i::cross(a, b)));
+}
+
 void Vector2Test::axes() {
     constexpr Vector2 x = Vector2::xAxis(5.0f);
     constexpr Vector2 y = Vector2::yAxis(6.0f);

src/Math/Test/Vector3Test.cpp

@@ -180,10 +180,10 @@ void Vector3Test::access() {
 }
 
 void Vector3Test::cross() {
-    Vector3 a(1, -1, 1);
-    Vector3 b(4, 3, 7);
+    Vector3i a(1, -1, 1);
+    Vector3i b(4, 3, 7);
 
-    CORRADE_COMPARE(Vector3::cross(a, b), Vector3(-10, -3, 7));
+    CORRADE_COMPARE(Vector3i::cross(a, b), Vector3i(-10, -3, 7));
 }
 
 void Vector3Test::axes() {

src/Math/Vector2.h

@@ -80,6 +80,20 @@ template<class T> class Vector2: public Vector<2, T> {
          */
         inline constexpr static Vector2<T> yScale(T scale) { return Vector2<T>(T(1), scale); }
 
+        /**
+         * @brief 2D cross product
+         *
+         * 2D version of cross product, equivalent to calling Vector3::cross()
+         * with Z coordinate set to `0` and extracting only Z coordinate from
+         * the result (X and Y coordinates are always zero).
+         * @f[
+         *      \boldsymbol a \times \boldsymbol b = a_xb_y - a_yb_x
+         * @f]
+         */
+        inline static T cross(const Vector2<T>& a, const Vector2<T>& b) {
+            return a.x()*b.y() - a.y()*b.x();
+        }
+
         /** @copydoc Vector::Vector() */
         inline constexpr /*implicit*/ Vector2() {}
 

src/Math/Vector3.h

@@ -102,12 +102,12 @@ template<class T> class Vector3: public Vector<3, T> {
          * @brief Cross product
          *
          * @f[
-         * \boldsymbol a \times \boldsymbol b =
-         * \begin{pmatrix} c_0 \\ c_1 \\ c_2 \end{pmatrix} =
-         * \begin{pmatrix}a_1b_2 - a_2b_1 \\ a_2b_0 - a_0b_2 \\ a_0b_1 - a_1b_0 \end{pmatrix}
+         *      \boldsymbol a \times \boldsymbol b =
+         *      \begin{pmatrix}a_yb_z - a_zb_y \\ a_zb_y - a_xb_z \\ a_xb_y - a_yb_x \end{pmatrix}
          * @f]
+         * @see Vector2::cross()
          */
-        inline constexpr static Vector3<T> cross(const Vector3<T>& a, const Vector3<T>& b) {
+        inline static Vector3<T> cross(const Vector3<T>& a, const Vector3<T>& b) {
             return swizzle<'y', 'z', 'x'>(a)*swizzle<'z', 'x', 'y'>(b) -
                    swizzle<'z', 'x', 'y'>(a)*swizzle<'y', 'z', 'x'>(b);
         }