[osg-users] OSG with Haptics

Adrian Egli OpenSceneGraph (3D) 3dhelp at gmail.com
Mon Jul 14 00:41:02 PDT 2008


Hi Matt,

i implemented once an haptic based application. most of the models are about
1M triangles, and no device can handle such numbre of tries. but finally the
app runs at 150Hz :-). so you can never get faster than 1000Hz for big
scene. ok i guess you are using the phantom device, and the vendor says:
it's running at 1000Hz,... you have to update the triangles for each frame,
or you pass the whole scene to the device, right. if you have to update you
can not pass it with 1000Hz as the device can render it. but no worries, the
device can only render 1000Hz with in an optimal case, and we never have
this case in our apps. how did i achieve +100Hz with such big scenes, i
implemented an kdTree to store the triangles, and then i culled them against
a sphere. so since OSG has kdTree support (since past week) may you can
implement a polytopIntersector, or just for a sphere. the sphere radius is
the max distance the device can move between one frame :-) the faster you
render the smaller the radius become, faster again ,... you see, quite
important.

so implement the polytop intersection, add a sphere or a box or ... it would
be greate if you could share the code. :-) new node kit or ...

what kind of driver you will support ?

adrian

2008/7/14 Matt Sutton <Matt.Sutton at padtinc.com>:

>
> Hi Folks,
>   I'm brand new to osg, so I wanted to get some feedback from more
> experienced users regarding a tactic I am considering for a haptic
> application I am developing.  Haptics are 3d force feedback devices.  One of
> the challenges with them is that they require update speeds at approximately
> 1000Hz.  The model that I will be working with is approximately 1,000,000
> triangles, so collision detection is challenging at these rates.  The tactic
> I am considering in a nut shell is to use a second scene graph for haptic
> culling purposes.  I want to create an artificial viewing frustum near the
> haptic probe so I can cull away triangles that cannot come into contact with
> the probe.  I would then use the haptic rendering software with this smaller
> subset of triangles.  The cull doesn't need to process at 1000Hz, but rather
> needs to maintain a window around the probe such that the "visible"
> triangles include all that can potentially contact the probe while the probe
> is moving and before the next cull frame.  Does this sound reasonable?  If
> so, what form should I use for my haptic scene graph?  That is, does the
> cull work best with a series of nodes representing smaller patches of the
> geometry?  Are there any issues, beyond the extra book-keeping with two
> separate scene graphs in a single application?  Is there any benefit in
> maintaining two separate graphs, or would alternate traversals of a master
> graph be sufficient?  Sorry if these are too elementary.  Please feel free
> to point me to a piece of documentation if I am missing something.
> Thanks for any help.
> Matt Sutton
> www.padtinc.com
>
> _______________________________________________
> osg-users mailing list
> osg-users at lists.openscenegraph.org
> http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
>
>


-- 
********************************************
Adrian Egli
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