LineSegmentIntersector and MODEL Frame

[Nonsanity]

I have a scene built with a few objects loaded, the most pertinent one being a large plane surface centered at the origin. I want to cast a ray from a particular point at a particular angle inside the scene and get a list of everything it intersects—both the point of intersection and the Node object. Most examples of using intersectors involve picking from the window, so I haven't seen exactly what I wanted. But from what I've read, the following should at least be close:

    Vec3d start( 0.0, 0.0, 100.0 );
    Vec3d end( 0.0, 0.0, -100.0 );
    ref_ptr<LineSegmentIntersector> intsec = new LineSegmentIntersector( Intersector::MODEL, start, end );
    IntersectionVisitor iv( intsec.get() );
    viewer.getCamera()->accept( iv );
    cout << intsec->containsIntersections() << endl;

My start and end points in this snippet are well above and well below the surface object. So that plane object should definitely be intersected by a line running between them. However the containsIntersections function always returns false.

Immediately after making this preliminary test pick, the program calls viewer.run() so I know everything is arranged as expected in the scene. So my guess is that I'm missunderstanding how the visitor works. Perhaps the accept() function is not what I should be using to execute the intersector?

 ~ Chris

[OpenSceneGraph Users]

Hi Chris,

I guess you want the scene to accept the IntersectionVisitor, not the camera.

Laurens.

--
You received this message because you are subscribed to the Google Groups "OpenSceneGraph Users" group.
To unsubscribe from this group and stop receiving emails from it, send an email to osg-users+...@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/osg-users/58d20034-cb65-4bef-937f-f85a1fa92030%40googlegroups.com.
_______________________________________________
osg-users mailing list
osg-...@lists.openscenegraph.org
http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org

[Nonsanity]

Thanks. I had thought to apply the visitor to the scene, but GetScene() didn't have Accept(). With your confirmation that using the scene was correct, I found that viewer.getSceneData()->accept( iv ) did exist.

However, calling that line just results in a segfault. The rest of the code is the same as before. I'm going to search to see if I'm doing something obviously wrong, but in case I got the above line incorrect, I wanted to post my failed results here for further comment.

On Monday, February 3, 2020 at 3:06:33 AM UTC-5, OpenSceneGraph Users wrote:

Hi Chris,

I guess you want the scene to accept the IntersectionVisitor, not the camera.

Laurens.

On Sat, Feb 1, 2020 at 1:18 PM OpenSceneGraph Users <osg-...@lists.openscenegraph.org> wrote:

I have a scene built with a few objects loaded, the most pertinent one being a large plane surface centered at the origin. I want to cast a ray from a particular point at a particular angle inside the scene and get a list of everything it intersects—both the point of intersection and the Node object. Most examples of using intersectors involve picking from the window, so I haven't seen exactly what I wanted. But from what I've read, the following should at least be close:

    Vec3d start( 0.0, 0.0, 100.0 );
    Vec3d end( 0.0, 0.0, -100.0 );
    ref_ptr<LineSegmentIntersector> intsec = new LineSegmentIntersector( Intersector::MODEL, start, end );
    IntersectionVisitor iv( intsec.get() );
    viewer.getCamera()->accept( iv );
    cout << intsec->containsIntersections() << endl;

My start and end points in this snippet are well above and well below the surface object. So that plane object should definitely be intersected by a line running between them. However the containsIntersections function always returns false.

Immediately after making this preliminary test pick, the program calls viewer.run() so I know everything is arranged as expected in the scene. So my guess is that I'm missunderstanding how the visitor works. Perhaps the accept() function is not what I should be using to execute the intersector?

 ~ Chris

--
You received this message because you are subscribed to the Google Groups "OpenSceneGraph Users" group.

To unsubscribe from this group and stop receiving emails from it, send an email to osg-...@googlegroups.com.

[Nonsanity]

I found the problem, and it was mine. It helps if I attach my root node to the scene BEFORE I try to insect with it. ;)