Revit.SDK.Samples.SlabShapeEditing.CS.Matrix4.Multiply C# (CSharp) Method

        public static Matrix4 Multiply(Matrix4 left, Matrix4 right)
        {
            Matrix4 result = new Matrix4();
            for (int i = 0; i < 4; i++)
            {
                for (int j = 0; j < 4; j++)
                {
                    result[i, j] = left[i, 0] * right[0, j] + left[i, 1] * right[1, j]
                        + left[i, 2] * right[2, j] + left[i, 3] * right[3, j];
                }
            }
            return result;
        }

        /// <summary>
        /// calculate the matrix used to transform 3D to 2D
        /// </summary>
        /// <returns>maxtrix is use to transform 3d points to 2d</returns>
        public Matrix4 Get3DTo2DMatrix()
        {
            Matrix4 result = Matrix4.Multiply(
                m_to2DMatrix.Inverse(), m_moveToCenterMatrix.Inverse());

            result = Matrix4.Multiply(result, m_scaleMatrix);
            return(Matrix4.Multiply(result, m_MoveToPictureBoxCenter));
        }