# [ODE] Convex Geometry

Pierre Renaux prenaux at alias25.org
Wed Apr 13 18:14:16 MST 2005

```Did you try to lower the number of updates per seconds (say 60 per
seconds) ?

Five hundreds sounds like a lot... Also what kind of application is it ?

Thanks,
- Pierre

>Surprisingly, one contact point is enough for our application. I
>actually thought that this would be the major obstacle, however it is
>not.
>
>Here's my interpretation: If two objects collide, that will take place
>over 1/10 of a second. Since collision detection runs 500 cycles per
>second, I get 50 penetration depth vectors. That's a lot of
>information to work with.
>
>But that's only guessing. Fact is, collision detection and handling works well.
>
>Harald
>
>
>
>On 4/13/05, Pierre Renaux <prenaux at alias25.org> wrote:
>
>
>>Hi,
>>
>>If you got only a penetration depth how to you convert that to the
>>several contact points required by ODE ? Or is that enought to convert
>>to one contact point ?
>>
>>- Pierre
>>
>>
>>
>>>I have combined ODE with SOLID, which uses GJK. It works perfectly
>>>well, although I have only the pentration depth to work with.
>>>
>>>A convex object is a convex set. And a convex set is defined as
>>>
>>>B is a convex set <=> for every x,y in B and any s in [0,1] it is true
>>>that z = s*x + (1-s)*y is in B.
>>>
>>>Or in words: A set is convex if for any two points in the set the line
>>>connecting the two points is also contained in the set.
>>>
>>>I don't know if there is such a thing as a concave set.
>>>
>>>Harald
>>>
>>>On Apr 12, 2005 7:24 PM, Jeffrey Smith <jeffreys at softimage.com> wrote:
>>>
>>>
>>>
>>>
>>>>Stephen say wrote:
>>>>
>>>>
>>>>
>>>>
>>>>>Just wondering if anyone has ever experiemented using a trimesh to simulate
>>>>>a convex geometry (like a bucket for example).
>>>>>
>>>>>
>>>>>
>>>>>
>>>>A bucket is actually conCAVE. Convex objects are locally spherical everywhere
>>>>(i.e. no cavities, dips or valleys).
>>>>
>>>>But to answer your question, trimesh vs. primitive collisions are relatively stable,
>>>>but trimesh/trimesh collisions remain problematic.  An implementation of GJK/EPA
>>>>would fit well into ODE, if you're looking for a "fun" project.
>>>>
>>>>-jeff
>>>>
>>>>_______________________________________________
>>>>ODE mailing list
>>>>ODE at q12.org
>>>>http://q12.org/mailman/listinfo/ode
>>>>
>>>>
>>>>
>>>>
>>>>
>>>
>>>
>>>
>>>
>>
>>
>
>
>
>

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