# [ODE] Boolean operation on collision geometry

Gary R. Van Sickle g.r.vansickle at worldnet.att.net
Fri Apr 8 02:31:37 MST 2005

```> Thanks Adam.
>
> Noticed that Christian Larsen in
> http://q12.org/pipermail/ode/2004-October/014181.html talked
> about a subtraction of a sphere from a box. I wonder if
> anyone has done this work (or similar) or not (other than of
> triangulation), as this particular case is just what I would
> like to achieve.
>
> Thanks
>
> Gao Yang
>

FWIW, I tried for a while to find something exactly like you're talking
about, but came up empty.  If papers addressing such an issue exist, I
couldn't find them on the web, though I would sure like to see them, because
it has the potential to make collision detection faster by (I suspect)
several O()rders of magnitude ;-).  What I finally decided to do is convex
polyhedral decomposition and then colliding the convex polyhedra, since I
have to do the decomposition for other reasons anyway.  But this ain't a
walk in the park either.

--
Gary R. Van Sickle

>
>
>
> > Gao Yang wrote:
> >
> >> dGeomTransform is able to composite multiple collision
> geometry into
> >> one. Here's my question: If the composition in creating
> >> dGeomTransform we call it an addition operation, is there
> any way to
> >> apply subtraction operation on collision geometry in forming a
> >> composite geom?
> >
> >
> > Very difficult - check the list archives (keyword probably 'CSG').
> > Not impossible, but (I think the conclusion was) it would require
> > being able to derive the intersection surface patches for
> all of the
> > supported ODE primitive collision combinations, and
> inside/outside CSG
> > between the resulting solids formed by those patches too.  No quick
> > hackaround.
> >