The vtkImageResliceMapper shows a black polygon when slice is out of bounds.
When scrolling through a volume with vtkImageResliceMapper, strange things happen when the slice plane moves beyond the volume bounds. With a straight-on view, a black rectangle is shown (as compared to VTK 6.3, where nothing is shown). With an orthogonal view (90 degree rotation), a black rectangle is shown that is displaced horizontally or vertically by the distance beyond the bounds. With an oblique view, after going out-of-bounds the polygon from the last in-bounds position is shown (as a black polygon), and is again displaced.
A work-around is to call SeparateWindowLevelOperationOff(), which causes the rectangle/polygon to become transparent (though it is still present).
The problem seems to be related to vtkOpenGLImageSliceMapper and its polygon-rendering code. When the slice plane moves of bounds, the last valid in-bounds polygon is displayed. It should instead either render an empty polygon, or not render at all. Note that the "Background" option that renders a complementary polygon must also be fixed: if there is no "foreground" polygon to display, the "Background" polygon must fill the entire view.
When fixing this, be sure to test the situation where the slice plane is out-of-bounds on the first render.
This is tangentially related to #16041.