[vtkusers] opacity problem / how to ensure btf rendering

[Simon Faust]

Hi,
again I want to visualize a building with some furniture using tcl. All
objects are cubes, with per-object color and per-object opacity and they
are long and thin sometimes. Problem was that when rotating/zooming
around/into the data the rendering was no longer correct but objects
from behind "jumped" into the foreground. This occured when opacity was
set near to 1. Several solutions were proposed: DepthSortPolyData does
not work for long thin primitives and just for one transparent object.
Sorting the objects backtTofront and rendering in this order did not
solve the whole problem, just brought little improvement, cause there is
no occlusion detection. Isn't there any (probably easy) way to achieve
correct rendering of my scene?
Thanks in advance, Regards Simon