Wow, so this is odd. I found a way to fix this.
I was using a linesegment length of 2.0, as I had a 2 ft stick attached
to the wand. But, if I make the linesegment longer, to a length of
200.0, the intersection works like a charm.
Is this the intended behavior?
Dave Pugmire wrote:
> Hi,
> I'm scratching my head on this one.
> I have a line segment, that is aligned to the tracked wand. I'm trying
> to intersect it with the scene, which is composed of a single box.
> However, the intersections that I get are not making sense.
>
> Here is the line segment, made from two points:
> p1 = ( -.24, 5.5, .033 ) p2 = (-.24 5.5 -1.96)
> Note that this is a line of constant Y=5.5
> Length of 2 along the -Z direction.
>
> The box is cenetered at 0, 4.5, -1, and has unit dimensions.
> The bounding box of the box is:
> xyzMin = [-.5, 4, -1.5] xyzMax = [.5, 5, -.5]
> The box has no transformations above it, it's a direct child of the
> scene root.
>
> When I run IntersectVisitor on the graph, it detects an intersection
> with the box at: [-.17, 4.0, -.88]
> Which is NOT on the LineSegment.
> I'm confused. Here is the code that I'm using.
> m_wandP1 and m_wandP2 are the two points mentioned above.
>
>
> Thanks,
> -dave
>
>
> void CWand::UpdateIntersect( osg::Group *pSceneRoot )
> {
> osg::Vec3 wandDir = m_wandP2 - m_wandP1;
>
> //Create a line segment for the wand end points.
>
> osg::ref_ptr<osg::LineSegment> wandStick = new osg::LineSegment(
> m_wandP2, -wandDir );
>
> //Intersect with the scene graph.
> osgUtil::IntersectVisitor intersectVisitor;
> intersectVisitor.setLODSelectionMode(
> osgUtil::IntersectVisitor::USE_HIGHEST_LEVEL_OF_DETAIL );
> intersectVisitor.addLineSegment( wandStick.get() );
> pSceneRoot->accept( intersectVisitor );
>
> if ( m_bPrintUpdate )
> printf( "Poke: P0 <%f %f %f> P1 <%f %f %f> Dir:[%f %f %f]\n\n",
> m_wandP1[0],m_wandP1[1],m_wandP1[2],
> m_wandP2[0],m_wandP2[1],m_wandP2[2],
> wandDir[0],wandDir[1],wandDir[2] );
>
> osgUtil:: IntersectVisitor::HitList htl =
> intersectVisitor.getHitList( wandStick.get() );
> vector<osg::Geode*> geodeHits;
> int numHits = 0;
> if ( htl.size() > 0 ) // We always hit the wand, so only consider
> "additional" hits.
> {
> for ( int i = 0; i < htl.size(); i++ )
> {
> osg::Vec3 pt = htl[i].getWorldIntersectPoint();
> osg::Vec3 n = htl[i].getWorldIntersectNormal();
> osg::NodePath np = htl[i].getNodePath();
> //osg::Vec3 pt = htl[i].getLocalIntersectPoint();
> osg::Vec3 dir = m_wandP1-pt;
>
> if ( true )
> {
> numHits++;
> geodeHits.push_back( htl[i].getGeode() );
>
> if ( m_bPrintUpdate )
> {
> printf( "\tIsect[%d]: %s D=%f [%f %f %f] Pt=<%f %f %f> N<%f
> %f
> %f>\n", numHits,
> htl[i].getGeode()->getName().c_str(),
> dir.length(),
> dir[0],dir[1],dir[2],pt[0],pt[1],pt[2],
> n[0],n[1],n[2] );
> osg::BoundingBox bb = htl[i].getGeode()->getBoundingBox();
> printf( "\tBBOX: [%f %f %f] [%f %f %f]\n",
> bb.xMin(),bb.yMin(),bb.zMin(),
> bb.xMax(),bb.yMax(),bb.zMax() );
> printf( "\t Node path:\n" );
> for ( int j = 0; j < np.size(); j++ )
> {
> osg::Node *node = np[j];
> printf( "\t%d: %s\n", j, node->className() );
>
> osg::MatrixTransform *pMT =
> dynamic_cast<osg::MatrixTransform*>(node);
> osg::PositionAttitudeTransform *pPAT =
> dynamic_cast<osg::PositionAttitudeTransform*>(node);
> if ( pMT != NULL ) //node->className() ==
> "MatrixTransform" )
> {
> osg::MatrixTransform *pMtx = (osg::MatrixTransform
> *) node;
> osg::Matrix mtx = pMtx->getMatrix();
> printf( "\t T[%f %f %f] [%f %f %f] [%f %f %f] [%f
> %f %f]\n",
> mtx(3,0),mtx(3,1),mtx(3,2),
> mtx(0,0),mtx(0,1),mtx(0,2),
> mtx(1,0),mtx(1,1),mtx(1,2),
> mtx(2,0),mtx(2,1),mtx(2,2) );
> }
> else if ( pPAT != NULL )
> {
> osg::Vec3 p = pPAT->getPosition();
> osg::Quat Q = pPAT->getAttitude();
> osg::Vec4 q = Q.asVec4();
> printf( "\t T[ %f %f %f] Q[%f %f %f %f]\n",
> p[0],p[1],p[2], q[0],q[1],q[2],q[3] );
> }
> else
> printf( "??\n" );
> }
>
> //osg::Matrix *mtx = (osg::Matrix*)htl[i].getMatrix();
> //printf( "\tRM: [%f %f %f]\n", (*mtx)(0,0), (*mtx)(0,1),
> (*mtx)(0,2) );
> }
> }
> }
> }
>
> m_wandShapeDrawable->setColor( (numHits > 0 ? m_IntersectColor :
> m_Color) );
>
> }
>
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