[Paraview-developers] Set up camera intrinsic matrix in python Paraview

[Li Guan]

Hi all,

I am trying to set up the camera view w.r.t. the camera matrix K in
Paraview python shell. Basically, I create an intrinsic matrix to store the
new projective matrix obtained from 3x3 camera intrinsic matrix K, get the
current projection transform matrix A, and create a new matrix apply_matrix,
as intrinsic/A, and apply it to vtk.vtkPerspectiveTransform() The code is
shown below. My question is if this code is correct? Because when I run the
script twice, the rendered views are a little bit different. And the third
time the view will become the same as the first time again. I wonder if
this is some numerical error or what I have done wrong? Many thanks!

Li

RenderView1 = GetRenderView();
[w, h]=RenderView1.GetRenderer().GetSize();
camera = RenderView1.GetActiveCamera();
[n, f] = camera.GetClippingRange();
print f,n;

A = camera.GetProjectionTransformMatrix(double(w)/double(h), -1.0, 1.0);

iIntrinsic = vtk.vtkMatrix4x4();
A.Invert(A, iIntrinsic);

intrinsic = vtk.vtkMatrix4x4();
intrinsic.SetElement(0,0,2.0*K.getA()[0][0]/double(w));
intrinsic.SetElement(0,1,-2.0*K.getA()[0][1]/double(w));
intrinsic.SetElement(0,2,-2.0*K.getA()[0][2]/double(w)+1.0);
intrinsic.SetElement(0,3,0.0);
intrinsic.SetElement(1,0,0.0);
intrinsic.SetElement(1,1,2.0*K.getA()[1][1]/double(h));
intrinsic.SetElement(1,2,-2.0*(double(h)-K.getA()[1][2])/double(h)+1.0);
intrinsic.SetElement(1,3,0.0);
intrinsic.SetElement(2,0,0.0);
intrinsic.SetElement(2,1,0.0);
intrinsic.SetElement(2,2,-(f+n)/(f-n));
intrinsic.SetElement(2,3,-2.0*f*n/(f-n));
intrinsic.SetElement(3,0,0.0);
intrinsic.SetElement(3,1,0.0);
intrinsic.SetElement(3,2,-1.0);
intrinsic.SetElement(3,3,0.0);

apply_matrix = vtk.vtkMatrix4x4();
apply_matrix.Multiply4x4(intrinsic, iIntrinsic, apply_matrix);
print "apply_matrix\n";
print apply_matrix;
T = vtk.vtkPerspectiveTransform();
T.SetMatrix(apply_matrix);

camera.SetUserTransform(T);
Render();
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