Matrix Multiplication And vtkTransform Concatenate

We can use vtkTransform’s function concatenate to do matrix multiplication.
There are three matrix which have the mathematical relationship.

It’s equivalent to the following code.

    vtkSPtrNew( C, vtkTransform );
    C->Concatenate(B);
    C->Concatenate(A);
    C->Update();

The experimental code:

#include <iostream>
#include <vtkSmartPointer.h>
#include <vtkTransform.h>

#define vtkSPtr vtkSmartPointer
#define vtkSPtrNew(Var, Type) vtkSPtr<Type> Var = vtkSPtr<Type>::New();

using namespace std;


int main()
{
    // B*A = C
    vtkSPtrNew( A, vtkTransform );
    double elementsA[16] = { 1,  0,  0,  1,
                             0,  1,  0,  1,
                             0,  0,  1,  0,
                             0,  0,  0,  1 };
    A->SetMatrix( elementsA );

    vtkSPtrNew( B, vtkTransform );
    double elementsB[16] = { 1,  0,  0,  0,
                             0,  0.939693,  -0.34202,  0,
                             0,  0.34202,  0.939693,  0,
                             0,  0,  0,  1 };
    B->SetMatrix( elementsB );

    vtkSPtrNew( C, vtkTransform );
    C->Concatenate(B);
    C->Concatenate(A);
    C->Update();
    C->PrintSelf( std::cout, vtkIndent() );
    return 0;
}