Near plane clipping problem with vktRenderer and vtkCamera
This issue was created automatically from an original Mantis Issue. Further discussion may take place here.
I have noticed that it is very easy to cause the near clipping plane to cut-off the model when in parallel projection mode.
I ran into this recently when adding a vtkBoxWidget and scaling a simple cube a few times after rotating it so that one of the corners points towards the viewer.
I tried calling vtkRenderer::ResetCameraClippingRange() to no avail. vtkRenderer::ResetCamera() fixed the problem, but would lose my camera setting.
After searching fruitlessly in the vtkusers archives, I decided to trace into the code and I discovered that there is code in vtkRenderer::ResetCameraClippingRange() and vtkCamera::SetClippingRange() that modifies the near plane value to "fix" potential camera and depth buffer problems. In my opinion, these fixes are valid, but only for perspective projections. For parallel projections, they are unnecessary and in fact cause the clipping problem I was encountering. To test this, I modified the code and rebuilt and lo and behold, no more near plane clipping!
Attached is my modified version of vtkCamera.cxx and vtkRenderer.cxx along with the patch files relative to version 5.2.0 (only vtkCamera.cxx has changed since then). The changes are small and localized.