[vtkusers] weird rendering, traced images

[Khew Sing Yoong]

hi all,

i am just doing something easy:

vtkSphereSource, vtkPolyData --> vtkGlyph3D --> vtkPolyDataMapper --> 
vtkActor

with the polydata defining a set of points. so that the sphere can be 
replicated on the scene.

all of this renders fine and dandy... until you start to 
rotate/move/zoom the rendering. then you can see traces of the motion of 
the spheres up until where you stop it.

these traces do not disappear until you minimize, then restore the 
window where the rendering is.

anyone had similar experiences who can help me figure this one out?

thanks in advance!

-y