Hi folks,
On Mon, 2004-02-16 at 05:18, Carsten Neumann wrote:
>
> I'm not sure if this is what you are asking for, but the IntersectAction
> starts the traversal at the Node you pass in (i.e. scene_root) and
> proceeds in the usual depth-first style. From the code you've given
> above I assume you only need the information if anything was hit, or
> maybe the geometry as well, but the IntersectAction will also determine
> the triangle that was hit. This is a likely the place where your
> performance hit comes from, as OpenSG has no special structure inside a
> Geometry to improve intersection on the triangle level. IIRC there is
> currently no way to turn off the triangle determination.
>
> >
> > does the intersect action use bounding boxes to fast discard negative
> > collisions??
>
> Yes, but this only helps if you have many Geometries, not when looking
> for a hit triangle inside a Geometry.
>
> Sorry, maybe someone else has some ideas here,
hm, not much we can do here. The main reason dedicated ray-tracers are
fast is because they add a lot of additional structure on the polygon
level, which you don't need for OpenGL rendering, which is why we don't
have any of that yet. Exception: polygon sorting for transparencies,
which is why we might it someday, but not right now.
The one thing that might help is Christoph Fuenfzig's work for OpenSG
Plus, which does add these kinds of polygon-based structures for quick
collision detection, for which ray intersection is a basic operation.
Christoph, can you comment on how hard it is to use your code for simple
ray intersection?
Thanks
Dirk
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