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# PerspectiveTransform

VTKEx/Java/SimpleOperations/PerspectiveTransform

Description:

The perspective transform automatically appends the "homogeneous 1" to the point before it is multiplied by the matrix. It then divides the first 3 coordinates of the result by the 4th coordinate of the result. For comparison, the standard projection vtkTransform) is also performed with the same matrix and the same point. Note that the results are much different.

Other languages

See (Cxx), (CSharp)

Question

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### Code

PerspectiveTransform.java

    import vtk.vtkNativeLibrary;
    import vtk.vtkPerspectiveTransform;
    import vtk.vtkTransform;
    import vtk.vtkMatrix4x4;

    public class PerspectiveTransform
    {
      // -----------------------------------------------------------------
      // Load VTK library and print which library was not properly loaded
      static
      {
        if (!vtkNativeLibrary.LoadAllNativeLibraries())
        {
          for (vtkNativeLibrary lib : vtkNativeLibrary.values())
          {
            if (!lib.IsLoaded())
            {
              System.out.println(lib.GetLibraryName() + " not loaded");
            }
          }
        }
        vtkNativeLibrary.DisableOutputWindow(null);
      }
      // -----------------------------------------------------------------

      public static void main(String s[])
      {
        vtkMatrix4x4 M = new vtkMatrix4x4();
        M.SetElement(0, 0, 1);
        M.SetElement(0, 1, 2);
        M.SetElement(0, 2, 3);
        M.SetElement(0, 3, 4);
        M.SetElement(1, 0, 2);
        M.SetElement(1, 1, 2);
        M.SetElement(1, 2, 3);
        M.SetElement(1, 3, 4);
        M.SetElement(2, 0, 3);
        M.SetElement(2, 1, 2);
        M.SetElement(2, 2, 1);
        M.SetElement(2, 3, 4);
        M.SetElement(3, 0, 4);
        M.SetElement(3, 1, 2);
        M.SetElement(3, 2, 3);
        M.SetElement(3, 3, 4);

        vtkPerspectiveTransform PT = new vtkPerspectiveTransform();
        PT.SetMatrix(M);

        vtkTransform Transform = new vtkTransform();
        Transform.SetMatrix(M);

        double p[] = new double[] {1.0,2.0,3.0};

        double normalProjection[] = new double[3];
        Transform.TransformPoint(p, normalProjection);
        System.out.println(normalProjection[0] + " " + normalProjection[1] + " " + normalProjection[2]);

        double perspectiveProjection[] = new double[3];
        PT.TransformPoint(p, perspectiveProjection);
        System.out.println(perspectiveProjection[0] + " " + perspectiveProjection[1] + " " + perspectiveProjection[2]);
      }
    }