[osg-users] picking behaviour using osgViewer::View::computeIntersections

[Robert Osfield]

Hi Glen,

In older versions of the OSG there were precision issues on some
databases when doing intersections, this might be happening in your
case. In OSG-3.4 there is support for doing double precision
intersection as well as tightening up of the code to better handle
precisions issues.

Particular problems used to occur when bounding boxes of geometries
were axis aligned so the bounding box was zero thickness.

Robert.

On 6 May 2016 at 21:46, Swanger, Glen T. <Glen.Swanger at jhuapl.edu> wrote:
> We are using the osgViewer::View::computeIntersections method to detect actionable elements in our scene as the mouse rolls over them in screen space so that we can highlight them for the user.  This works well in most cases, but for some geometry as you move the mouse over the same actionable element we may lose the intersection hit on that object; consequently, we remove the highlight from the object which leads to a confusing flashing effect for the user.  I ran our application in wireframe mode and saw that this problem occurs even if you move the mouse within the same triangle primitive.  I've made sure the window coordinates provided to the method are consistent with the mouse movement and I've logged the node paths for all the hits returned from this method to make sure I wasn't missing anything by looking at just the top most hit.  We compared our modeling techniques with geometry that doesn't result in this problem and nothing seems inconsistent.  Does anyone have an
>   idea what might be causing this problem, or point us to something else we can look at.
>
> Thanks,
> Glen
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