Re: [osg-users] cast ray into scene

[Sukender]

Hi Ben,

In my engine, I got a method that takes a View and an optional NodePath. Notes:
  - I created an invisible plane so that I can test against that plane.
  - pointerX and pointerY are class members (you may refactor so that it suits 
your needs).
  - Here my method assumes there is at most one intersection (see the ASSERT()).
  - setPickPosition() is a method that stores the result (= the 
intersection/pick position).

void computePickPos(osgViewer::View  view, osg::NodePath * pPickNodePath = 
NULL) {
if (pPickNodePath  pPickNodePath-empty()) return;
osgUtil::LineSegmentIntersector::Intersections intersections;
bool intersected;
if (pPickNodePath) intersected = view.computeIntersections(pointerX, 
pointerY, *pPickNodePath, intersections);
else intersected = view.computeIntersections(pointerX, pointerY, 
intersections);
if (intersected)
{
ASSERT(intersections.size() = 1);
if (intersections.size()0) 
setPickPosition(intersections.begin()-getWorldIntersectPoint());
}
}

Hope it helps.

Sukender
PVLE - Lightweight cross-platform game engine - http://pvle.sourceforge.net/


Le Mon, 09 Mar 2009 20:31:55 +0100, Ben Axelrod baxel...@coroware.com a écrit:

 I have been using osgUtil::PickVisitor for a while now to pick objects in my 
 tree under the mouse.  But now I need to cast a ray into the scene under the 
 mouse and manually intersect it with an imaginary plane.  Is there some 
 helper function to do this mouse ray cast for me?  Specifically, something 
 that would take as input 2 ints for the position of the mouse, and maybe the 
 camera or projection and view matrices, then output a vector?

 Thanks,
 -Ben
 

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[osg-users] cast ray into scene

[Ben Axelrod]

I have been using osgUtil::PickVisitor for a while now to pick objects in my 
tree under the mouse.  But now I need to cast a ray into the scene under the 
mouse and manually intersect it with an imaginary plane.  Is there some helper 
function to do this mouse ray cast for me?  Specifically, something that would 
take as input 2 ints for the position of the mouse, and maybe the camera or 
projection and view matrices, then output a vector?

Thanks,
-Ben
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Re: [osg-users] cast ray into scene

[John Aughey]

For my application, I use this function to extract the origin and the
direction of a 2d point on the screen.  My windowing system here is Qt.

I can't say this is the most efficient way to get the answer, but it works.

void QOpenSceneGraph::xyVector(const QPoint screenpoint, osg::Vec3d
origin, osg::Vec3d direction)
{
osg::Matrix mat =
osg::Matrix::inverse(m_SceneView-getProjectionMatrix());

osg::Matrix cameramatrix = this-getCameraMatrix();
osg::Matrix cameramatrixnotrans = cameramatrix;
cameramatrixnotrans.setTrans(0,0,0);

osg::Vec4d d = osg::Vec4(
((double)screenpoint.x() / (double)this-width()) * 2.0 -
1.0,
-(((double)screenpoint.y() / (double)this-height()) * 2.0 -
1.0),
0.0,1.0);
d = d * mat;
d = d * cameramatrixnotrans;

direction.set(d[0],d[1],d[2]);
direction.normalize();

origin = cameramatrix.getTrans();
}


On Mon, Mar 9, 2009 at 2:31 PM, Ben Axelrod baxel...@coroware.com wrote:

  I have been using osgUtil::PickVisitor for a while now to pick objects in
 my tree under the mouse.  But now I need to cast a ray into the scene under
 the mouse and manually intersect it with an imaginary plane.  Is there some
 helper function to do this mouse ray cast for me?  Specifically, something
 that would take as input 2 ints for the position of the mouse, and maybe the
 camera or projection and view matrices, then output a vector?



 Thanks,

 -Ben

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 osg-users@lists.openscenegraph.org
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