[vtkusers] Obtain a mesh orthographic projections

[Bruno Cafaro]

Dear vtkUsers,
i have a mesh, and i need to extract its orthographic projections on the 
three planes 'xy', 'xz' and 'yz'.

Here is my code snippet:

void ImplicitFunctionRender::GetOrtho(float d)
{
     // 'XY' plane
     camera->SetPosition(0,0,d);
     camera->SetViewUp(0,1,0);
     camera->SetViewPlaneNormal(0,0,-1);

     ImplicitFunctionRender::SavePNG(11,0);
ImplicitFunctionRender::SaveTRANSFORM4x4(11,0,camera->GetViewPlaneNormal(),camera->GetPosition(),camera->GetViewUp());

     // 'YZ' plane
     camera->SetPosition(0,d,0);
     camera->SetViewUp(1,0,0);
     camera->SetViewPlaneNormal(0,-1,0);

     ImplicitFunctionRender::SavePNG(22,0);
ImplicitFunctionRender::SaveTRANSFORM4x4(22,0,camera->GetViewPlaneNormal(),camera->GetPosition(),camera->GetViewUp());

     // 'XZ' plane
     camera->SetPosition(d,0,0);
     camera->SetViewUp(0,0,1);
     camera->SetViewPlaneNormal(-1,0,0);

     ImplicitFunctionRender::SavePNG(33,0);
ImplicitFunctionRender::SaveTRANSFORM4x4(33,0,camera->GetViewPlaneNormal(),camera->GetPosition(),camera->GetViewUp());
}

If I set View Up always to (0,0,1), which should be coherent with the 
'z' direction, in the second case 'YZ' plane i get an empty image. First 
and third are ok.
If I set View Up as in the code snippet I always have the object in the 
image, it works but in the 'YZ' plane case the image is rotated 90°, 
which is correct i suppose, but I want it again with 'Z' axis up....
Moreover setting or do not setting the view plane normal does not affect 
the results.

I also attach my results using the code snippet reported.

Hope someone can help me understanding how this work.

Best

Bruno
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