[vtkusers] actor always visible even when behind other actor

[Roel van der Kraan]

Dear all,

I have a VTK scene with 2 actors. one is an iso surface and the other 
actor is an object that is interactivly placed on the iso surface by 
moving the mouse around. I map the mouselocation onto the iso surface to 
get the the x, y, z of the object. But, sometimes parts of the object 
disappear behind the surface, because it intersects with the surface. I 
want the second actor always on top, so it has to be visible all the time, 
even when it is located 'behind' the iso surface.

Is there some way to disable the depth-buffer for one actor while 
rendering? The actor really needs to be placed on the x, y, z of the 
isosurface (for perspective reasons), so moving it slightly towards the 
camera position is not acceptable.

Thanks!

Roel van der Kraan