Add method to translate QgsMatrix4x4 by QgsVector3D

python/core/auto_generated/qgsmatrix4x4.sip.in

@@ -51,6 +51,11 @@ Initializes matrix by setting all values in row-major order
     QList< double > dataList() const /PyName=data,HoldGIL/;
 %Docstring
 Returns matrix data (in column-major order)
+%End
+
+    void translate( const QgsVector3D &vector );
+%Docstring
+Multiplies this matrix by another that translates coordinates by the components of a ``vector``.
 %End
 
     QgsVector3D map( const QgsVector3D &vector ) const /HoldGIL/;

src/core/qgsmatrix4x4.cpp

@@ -29,6 +29,13 @@ QgsMatrix4x4::QgsMatrix4x4( double m11, double m12, double m13, double m14,
   m[3][0] = m14; m[3][1] = m24; m[3][2] = m34; m[3][3] = m44;
 }
 
+void QgsMatrix4x4::translate( const QgsVector3D &vector )
+{
+  m[3][0] += m[0][0] * vector.x() + m[1][0] * vector.y() + m[2][0] * vector.z();
+  m[3][1] += m[0][1] * vector.x() + m[1][1] * vector.y() + m[2][1] * vector.z();
+  m[3][2] += m[0][2] * vector.x() + m[1][2] * vector.y() + m[2][2] * vector.z();
+  m[3][3] += m[0][3] * vector.x() + m[1][3] * vector.y() + m[2][3] * vector.z();
+}
 
 QList< double > QgsMatrix4x4::dataList() const
 {

src/core/qgsmatrix4x4.h

@@ -71,6 +71,11 @@ class CORE_EXPORT QgsMatrix4x4
     //! Returns matrix data (in column-major order)
     QList< double > dataList() const SIP_PYNAME( data ) SIP_HOLDGIL;
 
+    /**
+     * Multiplies this matrix by another that translates coordinates by the components of a \a vector.
+     */
+    void translate( const QgsVector3D &vector );
+
     //! Matrix-vector multiplication (vector is converted to homogenous coordinates [X,Y,Z,1] and back)
     QgsVector3D map( const QgsVector3D &vector ) const SIP_HOLDGIL
     {

tests/src/python/test_qgsmatrix4x4.py

@@ -78,6 +78,22 @@ class TestQgsMatrix4x4(QgisTestCase):
                              13, 14, 15, 16])])
             )
 
+    def test_translate(self):
+        """
+        Test translating a matrix
+        """
+        m = QgsMatrix4x4()
+        m.translate(QgsVector3D(1, 2, 3))
+        self.assertEqual(m.data(), [1.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 1.0, 2.0, 3.0, 1.0])
+
+        m = QgsMatrix4x4(1, 2, 3, 4,
+                         5, 6, 7, 8,
+                         9, 10, 11, 12,
+                         0, 0, 0, 1)
+
+        m.translate(QgsVector3D(1, 2, 3))
+        self.assertEqual(m.data(), [1.0, 5.0, 9.0, 0.0, 2.0, 6.0, 10.0, 0.0, 3.0, 7.0, 11.0, 0.0, 18.0, 46.0, 74.0, 1.0])
+
 
 if __name__ == '__main__':
     unittest.main()