[ODE] Should trimeshes react to physics?

[Nguyen Binh]

Keith!
Generally, the thing you described is caused  by misleading vertex/edge  or
vertex/vertex collision. There are cases that force the collision detection
decide what type of collision vertex/vertex, vertex/edge, or edge/edge. If
the decision is wrong, you might get a completly wrong penetration depth.

On 12/9/05, Keith Wiley <kwiley at cs.unm.edu> wrote:
>
> I've been having similar problems.  I'm using a trimesh as a terrain
> (not really hi res mind you).  I have rectangular blocks sitting on
> the terrain.  For the most part it works really well, but
> occasionally one of the blocks suddenly explodes upward with great
> force.  I'm pretty certain the cause of this is that the block is
> allowed to fall through the trimesh a little bit and then suddenly
> the collision gets detected and the block is eject forcefully from
> the collision.  I think decreasing the step size might help, but it's
> still confusing sphere behave just fine with trimeshes, and more to
> the point, the error results from the block falling into the trimesh
> for a few consecutive frames, so over the span of multiple calls to
> step the simulation forward the collisions is missed, allowing the
> block to fall partly into the trimesh.  I don't see how a smaller
> step size would help alleviate a problem that spans multiple
> consecutive calls to the world stepper.
>
> On Dec 8, 2005, at 3:31 PM, Marco Grubert wrote:
>
> > Jon Watte wrote:
> >> Trimeshes have been around for years, and are stable, as long as you
> >> don't try colliding them against other trimeshes.
> >
> > Even when limited to box collisions, trimeshes are not all that
> > stable. It
> > mostly depends on the spacing of triangles. If there are few
> > triangles the
> > results are quite good, but with higher density meshes (e.g.
> > terrain) the
> > collider creates too many and often times conflicting contacts that
> > break
> > the solver.
> >
> > - Marco Grubert
> >
> > _______________________________________________
> > ODE mailing list
> > ODE at q12.org
> > http://q12.org/mailman/listinfo/ode
>
>
> ________________________________________________________________________
> Keith Wiley         kwiley at cs.unm.edu         http://www.unm.edu/~keithw
>
> "I do not feel obliged to believe that the same God who has endowed us
> with sense, reason, and intellect has intended us to forgo their use."
>                                             --  Galileo Galilei
> ________________________________________________________________________
>
> _______________________________________________
> ODE mailing list
> ODE at q12.org
> http://q12.org/mailman/listinfo/ode
>



--
--------------------------------------------------
Binh Nguyen
Computer Science Department
Rensselaer Polytechnic Institute
Troy, NY, 12180
--------------------------------------------------
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://q12.org/pipermail/ode/attachments/20051209/03ee0cfd/attachment.htm