Assuming the vectors are normalized in Matrix4::rotation().

src/Math/Matrix4.h

@@ -69,36 +69,39 @@ template<class T> class Matrix4: public Matrix<4, T> {
         /**
          * @brief 3D rotation matrix
          * @param angle Rotation angle (counterclockwise, in radians)
-         * @param vec   Rotation vector
+         * @param vec   Normalized rotation vector
          *
-         * @see Matrix3::rotation(), Vector3::xAxis(), Vector3::yAxis(), Vector3::zAxis(), deg(), rad()
-         * @todo optimize - Assume the vectors are normalized?
+         * @see Matrix3::rotation(), Vector3::xAxis(), Vector3::yAxis(),
+         *      Vector3::zAxis(), deg(), rad()
+         * @attention Assertion fails on non-normalized rotation vector and
+         *      identity matrix is returned.
          */
         static Matrix4<T> rotation(T angle, const Vector3<T>& vec) {
-            Vector3<T> vn = vec.normalized();
+            CORRADE_ASSERT(MathTypeTraits<T>::equals(vec.dot(), T(1)),
+                           "Math::Matrix4::rotation(): vector must be normalized", {});
 
             T sine = std::sin(angle);
             T cosine = std::cos(angle);
             T oneMinusCosine = T(1) - cosine;
 
-            T xx = vn.x()*vn.x();
-            T xy = vn.x()*vn.y();
-            T xz = vn.x()*vn.z();
-            T yy = vn.y()*vn.y();
-            T yz = vn.y()*vn.z();
-            T zz = vn.z()*vn.z();
+            T xx = vec.x()*vec.x();
+            T xy = vec.x()*vec.y();
+            T xz = vec.x()*vec.z();
+            T yy = vec.y()*vec.y();
+            T yz = vec.y()*vec.z();
+            T zz = vec.z()*vec.z();
 
             return Matrix4<T>( /* Column-major! */
                 cosine + xx*oneMinusCosine,
-                    xy*oneMinusCosine + vn.z()*sine,
-                        xz*oneMinusCosine - vn.y()*sine,
+                    xy*oneMinusCosine + vec.z()*sine,
+                        xz*oneMinusCosine - vec.y()*sine,
                            T(0),
-                xy*oneMinusCosine - vn.z()*sine,
+                xy*oneMinusCosine - vec.z()*sine,
                     cosine + yy*oneMinusCosine,
-                        yz*oneMinusCosine + vn.x()*sine,
+                        yz*oneMinusCosine + vec.x()*sine,
                            T(0),
-                xz*oneMinusCosine + vn.y()*sine,
-                    yz*oneMinusCosine - vn.x()*sine,
+                xz*oneMinusCosine + vec.y()*sine,
+                    yz*oneMinusCosine - vec.x()*sine,
                         cosine + zz*oneMinusCosine,
                            T(0),
                 T(0), T(0), T(0), T(1)

src/Math/Test/CMakeLists.txt

@@ -5,7 +5,6 @@ corrade_add_test2(MathMathTypeTraitsTest MathTypeTraitsTest.cpp)
 corrade_add_test2(MathRectangularMatrixTest RectangularMatrixTest.cpp)
 
 corrade_add_test2(MathVectorTest VectorTest.cpp)
-set_target_properties(MathVectorTest PROPERTIES COMPILE_FLAGS -DCORRADE_GRACEFUL_ASSERT)
 corrade_add_test2(MathVector2Test Vector2Test.cpp)
 corrade_add_test2(MathVector3Test Vector3Test.cpp)
 corrade_add_test2(MathVector4Test Vector4Test.cpp)
@@ -16,3 +15,5 @@ corrade_add_test2(MathPoint3DTest Point3DTest.cpp)
 corrade_add_test2(MathMatrixTest MatrixTest.cpp)
 corrade_add_test2(MathMatrix3Test Matrix3Test.cpp)
 corrade_add_test2(MathMatrix4Test Matrix4Test.cpp)
+
+set_target_properties(MathVectorTest MathMatrix4Test PROPERTIES COMPILE_FLAGS -DCORRADE_GRACEFUL_ASSERT)

src/Math/Test/Matrix4Test.cpp

@@ -29,6 +29,7 @@ namespace Magnum { namespace Math { namespace Test {
 
 typedef Math::Matrix4<float> Matrix4;
 typedef Math::Matrix3<float> Matrix3;
+typedef Math::Vector3<float> Vector3;
 
 Matrix4Test::Matrix4Test() {
     addTests(&Matrix4Test::constructIdentity,
@@ -88,14 +89,19 @@ void Matrix4Test::scaling() {
 }
 
 void Matrix4Test::rotation() {
+    ostringstream o;
+    Error::setOutput(&o);
+
+    CORRADE_COMPARE(Matrix4::rotation(deg(-74.0f), {-1.0f, 2.0f, 2.0f}), Matrix4());
+    CORRADE_COMPARE(o.str(), "Math::Matrix4::rotation(): vector must be normalized\n");
+
     Matrix4 matrix(
          0.35612214f, -0.80181062f,   0.47987163f, 0.0f,
          0.47987163f,  0.59757638f,   0.6423595f,  0.0f,
         -0.80181062f,  0.0015183985f, 0.59757638f, 0.0f,
          0.0f,         0.0f,          0.0f,        1.0f
     );
-
-    CORRADE_COMPARE(Matrix4::rotation(deg(-74.0f), {-1.0f, 2.0f, 2.0f}), matrix);
+    CORRADE_COMPARE(Matrix4::rotation(deg(-74.0f), Vector3(-1.0f, 2.0f, 2.0f).normalized()), matrix);
 }
 
 void Matrix4Test::rotationScalingPart() {
@@ -122,10 +128,10 @@ void Matrix4Test::rotationPart() {
         -0.80181062f, 0.0015183985f, 0.59757638f
     );
 
-    Matrix4 rotation = Matrix4::rotation(deg(-74.0f), {-1.0f, 2.0f, 2.0f});
+    Matrix4 rotation = Matrix4::rotation(deg(-74.0f), Vector3(-1.0f, 2.0f, 2.0f).normalized());
     CORRADE_COMPARE(rotation.rotation(), expectedRotationPart);
 
-    Matrix4 rotationTransformed = Matrix4::translation({2.0f, 5.0f, -3.0f})*rotation*Matrix4::scaling(Vector3<float>(9.0f));
+    Matrix4 rotationTransformed = Matrix4::translation({2.0f, 5.0f, -3.0f})*rotation*Matrix4::scaling(Vector3(9.0f));
     CORRADE_COMPARE(rotationTransformed.rotation(), expectedRotationPart);
 }