Hi Julien-Charles,
Julien-Charles Levesque schrieb:
Hi,
I'm trying to use a PolytopeIntersector in my scene and so far I have succeeded but only by using the camera (i.e. mCamera->accept(PolyVisitor)) with a PolytopeIntersector built from x and y coordinates in window frame. However I would rather pass the visitor the root of my scene. I am doing this in a virtual reality project, and using the camera seems to complicate things a fair bit because we modify projection matrices and viewports a whole lot.
For my LineSegmentIntersector I have used 3D points in model space, which
worked fine when visiting the root of the scene. For the PolytopeIntersector I
am unsure how to do this... Only examples I have found so far used either
coordinates in projection space or coordinates in window space.
Yes, the examples do not use all available constructors of
PolytopeIntersector.
That is something that has been sitting on my to-do-list for a long time...
Now I have seen the CoordinateFrame MODEL or VIEW in the PolytopeIntersector
constructor, but I am unsure as how to use it. I have seen that the Znear plane
is fixed to 0 for MODEL and VIEW coordinate frames.. Does this mean that any
object behind Z=0 could not be intersected?
I also have a bad feeling that building and using the PolytopeIntersector in MODEL and VIEW coordinate frames will make it just rectangular instead of pyramidal.
There are two constructors that should be suitable for your use-case:
/** Construct a PolytopeIntersector using specified polytope in
MODEL coordinates.*/
PolytopeIntersector(const osg::Polytope& polytope);
/** Construct a PolytopeIntersector using specified polytope in
specified coordinate frame.*/
PolytopeIntersector(CoordinateFrame cf,
const osg::Polytope& polytope);
You can pass an arbitrary Polytope which does not have to be
rectangular.
To recapitulate : I am trying to build a polytpe intersector from one 3d point in model space (or world space) and it's orientation. I would prefer this polytope intersector to be independent from the cameras or viewports. I am stuck at this point. Am I assuming something wrong? Did I miss something that could make this simpler? Do you have any clue that could help me? Am I even making sense? :D
Try using one of the contructors above with a polytope that you
provide and use the MODEL coordinate frame. That should work.
Thank a lot,
Sincerely,
Julien-Charles
Cheers,
Peter
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