Hi Adrian, Thank you for the ideas. Yes, it is the Phantom 6DOF device. I'm skeptical as well that we'll be able to maintain 1000Hz. One other option I'm looking at is a voxel based approach where I use Google's sparsehash code to implement the voxel storage. It has its own set of limitations on resolution in particular, but has the one nice feature of being more or less constant complexity for a lookup vs a tree implementation. You just hash on 3D points and use a force field function that is stored in each voxel that is populated, otherwise force = 0. Resolution and static objects that aren't always static become challenging, however.
Thanks again, Matt From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Adrian Egli OpenSceneGraph (3D) Sent: Monday, July 14, 2008 12:41 AM To: OpenSceneGraph Users Subject: Re: [osg-users] OSG with Haptics 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 <[EMAIL PROTECTED]>: 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 [email protected] http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.or g -- ******************************************** Adrian Egli
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