Allow to specify value on diagonal in identity matrix constructor.

src/Math/Matrix.h

@@ -90,12 +90,13 @@ template<class T, size_t size> class Matrix {
          * @brief Default constructor
          *
          * You can also explicitly call this constructor with
-         * `Matrix m(Matrix::Identity);`.
+         * `Matrix m(Matrix::Identity);`. Optional parameter @p value allows
+         * you to specify value on diagonal.
          */
-        inline explicit Matrix(IdentityType = Identity): _data() {
+        inline explicit Matrix(IdentityType = Identity, T value = T(1)): _data() {
             /** @todo constexpr how? */
             for(size_t i = 0; i != size; ++i)
-                _data[size*i+i] = static_cast<T>(1);
+                _data[size*i+i] = value;
         }
 
         #ifndef DOXYGEN_GENERATING_OUTPUT

src/Math/Matrix3.h

@@ -46,11 +46,11 @@ template<class T> class Matrix3: public Matrix<T, 3> {
         inline constexpr explicit Matrix3(typename Matrix<T, 3>::ZeroType): Matrix<T, 3>(Matrix<T, 3>::Zero) {}
 
         /** @copydoc Matrix::Matrix(IdentityType) */
-        inline constexpr explicit Matrix3(typename Matrix<T, 3>::IdentityType = Matrix<T, 3>::Identity): Matrix<T, 3>{
+        inline constexpr explicit Matrix3(typename Matrix<T, 3>::IdentityType = Matrix<T, 3>::Identity, T value = T(1)): Matrix<T, 3>{
             /** @todo Make this in Matrix itself, after it will be constexpr */
-            1.0f, 0.0f, 0.0f,
-            0.0f, 1.0f, 0.0f,
-            0.0f, 0.0f, 1.0f
+            value, 0.0f, 0.0f,
+            0.0f, value, 0.0f,
+            0.0f, 0.0f, value
         } {}
 
         #ifndef DOXYGEN_GENERATING_OUTPUT

src/Math/Matrix4.h

@@ -114,12 +114,12 @@ template<class T> class Matrix4: public Matrix<T, 4> {
         inline constexpr explicit Matrix4(typename Matrix<T, 4>::ZeroType): Matrix<T, 3>(Matrix<T, 3>::Zero) {}
 
         /** @copydoc Matrix::Matrix(IdentityType) */
-        inline constexpr explicit Matrix4(typename Matrix<T, 4>::IdentityType = Matrix<T, 4>::Identity): Matrix<T, 4>{
+        inline constexpr explicit Matrix4(typename Matrix<T, 4>::IdentityType = Matrix<T, 4>::Identity, T value = T(1)): Matrix<T, 4>{
             /** @todo Make this in Matrix itself, after it will be constexpr */
-            1.0f, 0.0f, 0.0f, 0.0f,
-            0.0f, 1.0f, 0.0f, 0.0f,
-            0.0f, 0.0f, 1.0f, 0.0f,
-            0.0f, 0.0f, 0.0f, 1.0f
+            value, 0.0f, 0.0f, 0.0f,
+            0.0f, value, 0.0f, 0.0f,
+            0.0f, 0.0f, value, 0.0f,
+            0.0f, 0.0f, 0.0f, value
         } {}
 
         #ifndef DOXYGEN_GENERATING_OUTPUT

src/Math/Test/Matrix3Test.cpp

@@ -29,6 +29,28 @@ namespace Magnum { namespace Math { namespace Test {
 
 typedef Math::Matrix3<float> Matrix3;
 
+void Matrix3Test::constructIdentity() {
+    Matrix3 identity;
+    Matrix3 identity2(Matrix3::Identity);
+    Matrix3 identity3(Matrix3::Identity, 4.0f);
+
+    Matrix3 identityExpected(
+        1.0f, 0.0f, 0.0f,
+        0.0f, 1.0f, 0.0f,
+        0.0f, 0.0f, 1.0f
+    );
+
+    Matrix3 identity3Expected(
+        4.0f, 0.0f, 0.0f,
+        0.0f, 4.0f, 0.0f,
+        0.0f, 0.0f, 4.0f
+    );
+
+    QVERIFY(identity == identityExpected);
+    QVERIFY(identity2 == identityExpected);
+    QVERIFY(identity3 == identity3Expected);
+}
+
 void Matrix3Test::debug() {
     Matrix3 m(
         3.0f, 5.0f, 8.0f,

src/Math/Test/Matrix3Test.h

@@ -23,6 +23,8 @@ class Matrix3Test: public QObject {
     Q_OBJECT
 
     private slots:
+        void constructIdentity();
+
         void debug();
 };
 

src/Math/Test/Matrix4Test.cpp

@@ -31,6 +31,30 @@ namespace Magnum { namespace Math { namespace Test {
 typedef Math::Matrix4<float> Matrix4;
 typedef Math::Matrix3<float> Matrix3;
 
+void Matrix4Test::constructIdentity() {
+    Matrix4 identity;
+    Matrix4 identity2(Matrix4::Identity);
+    Matrix4 identity3(Matrix4::Identity, 4.0f);
+
+    Matrix4 identityExpected(
+        1.0f, 0.0f, 0.0f, 0.0f,
+        0.0f, 1.0f, 0.0f, 0.0f,
+        0.0f, 0.0f, 1.0f, 0.0f,
+        0.0f, 0.0f, 0.0f, 1.0f
+    );
+
+    Matrix4 identity3Expected(
+        4.0f, 0.0f, 0.0f, 0.0f,
+        0.0f, 4.0f, 0.0f, 0.0f,
+        0.0f, 0.0f, 4.0f, 0.0f,
+        0.0f, 0.0f, 0.0f, 4.0f
+    );
+
+    QVERIFY(identity == identityExpected);
+    QVERIFY(identity2 == identityExpected);
+    QVERIFY(identity3 == identity3Expected);
+}
+
 void Matrix4Test::translation() {
     Matrix4 matrix(
         1.0f, 0.0f, 0.0f, 0.0f,

src/Math/Test/Matrix4Test.h

@@ -23,6 +23,8 @@ class Matrix4Test: public QObject {
     Q_OBJECT
 
     private slots:
+        void constructIdentity();
+
         void translation();
         void scaling();
         void rotation();

src/Math/Test/MatrixTest.cpp

@@ -66,6 +66,7 @@ void MatrixTest::constructFromVectors() {
 void MatrixTest::constructIdentity() {
     Matrix4 identity;
     Matrix4 identity2(Matrix4::Identity);
+    Matrix4 identity3(Matrix4::Identity, 4.0f);
 
     Matrix4 identityExpected(
         1.0f, 0.0f, 0.0f, 0.0f,
@@ -74,8 +75,16 @@ void MatrixTest::constructIdentity() {
         0.0f, 0.0f, 0.0f, 1.0f
     );
 
+    Matrix4 identity3Expected(
+        4.0f, 0.0f, 0.0f, 0.0f,
+        0.0f, 4.0f, 0.0f, 0.0f,
+        0.0f, 0.0f, 4.0f, 0.0f,
+        0.0f, 0.0f, 0.0f, 4.0f
+    );
+
     QVERIFY(identity == identityExpected);
     QVERIFY(identity2 == identityExpected);
+    QVERIFY(identity3 == identity3Expected);
 }
 
 void MatrixTest::constructZero() {