VtkRenderer error

Support
1

Hi,
I am getting “Re-setting view-up since view plane normal is parallel” runtime error message arising from …\Rendering\Core\vtkRenderer.cxx line 1175

This error message is showing when I move the outline box to view the top of the box. (screenshot attached)

Capture-vtk

I am using VTK8.2.
Is there any way to suppress/resolve this message?

Thanks.

2

Hi there,

To achieve that effect one can, for instance, rotate the camera around the box. Do you have code that moves your camera? I’m asking this because I’ve seen camera-moving code lacking a due update of the view-up vector (done via vtkCamera::SetViewUp()) as many people think it is done automatically. My project has such code (e.g. to reset the scene to look down the X axis) and I have always to update it to get it right:

´void View3DWidget::onLookAtXY()
{
    //_renderer->ResetCamera();
    double *fp = _rendererMainScene->GetActiveCamera()->GetFocalPoint();
    double *p = _rendererMainScene->GetActiveCamera()->GetPosition();
    double dist
        = std::sqrt((p[0] - fp[0]) * (p[0] - fp[0]) + (p[1] - fp[1]) * (p[1] - fp[1])
                    + (p[2] - fp[2]) * (p[2] - fp[2]));
    _rendererMainScene->GetActiveCamera()->SetPosition(fp[0], fp[1], fp[2] + dist);
    _rendererMainScene->GetActiveCamera()->SetViewUp(0.0, 1.0, 0.0);
    // redraw the scene
    _vtkwidget->GetRenderWindow()->Render();
}

regards,

Paulo

3

Many thanks you Paulo.
It worked! :+1:

1 Like
4

Hello,

I’m glad to help. Here’s the role of the view-up vector if I was not very clear:

image
image750×482 42.1 KB

As you can see, setting only the camera’s focal point (“orientation” in the figure above) and position is not enough to define the viewing geometry. The view-up vector tells the renderer where the “up” of the camera is pointing to. The view-up vector should, under normal circumstances, be orthogonal to the normal vector of viewing plane (the blue panel in the figure). Setting it parallel to the normal would result in ill-conditioned matrices and divisions by zero in the computations down the rendering pipeline. Hence the VTK error.

take care,

Paulo

1 Like
5

You have summarized it very clearly and yet so precise :ok_hand:

1 Like