Hello Michael,
Michael Raab wrote:
> we're using OpenSG1.8 in our VR application.
> We have some problems rendering (semi-)transparent objects. The correct
> rendering of these objects depends on the viewing position. So my guess is
> that there might be something wrong with sorting of objects during rendering.
>
> - Is that a known problem? If yes, are there things that we can do to avoid
> this?
to render transparent objects correctly the individual polygons have to
be rendered in a defined order (back to front, or the other way around).
In other words one needs to do depth peeling to get this right, but
that is not implemented in OpenSG at the moment.
Instead OpenSG sorts transparent objects from back to front based on the
distance of the center of the bounding box to the camera. This only
approximates the correct ordering of polygons and limitations when it
comes to large or intersecting objects [1].
It generally helps to keep transparent objects small (maybe even by
splitting larger objects) and far apart from each other, if possible.
What do your scenes typically look like? Are there any assumptions you
can make about the position of transparent objects to each other?
Cheers,
Carsten
[1] In general it also gives incorrect results if the objects has a
closed surface (e.g. a surface) and you do not use backface culling.
Backfacing polygons could be rendered after front facing ones and give
incorrect blending results.
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