Thread: [Algorithms] Collisions with VIPM

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Hi,

How can be done fast collision detection with VIPM when it's always
changing its morphology?, using an static version of the mesh with all
desired polys?

Or, even better, using a static version of the mesh with *fewer*
polys.  Better still, use a sphere-tree or OBB-tree fit to
the mesh with roughly 100 spheres and/or OBB's.

At 12:24 AM 8/4/2000 +0200, you wrote:
>Hi,
>
>How can be done fast collision detection with VIPM when it's always
>changing its morphology?, using an static version of the mesh with all
>desired polys?
>
>
>_______________________________________________
>GDAlgorithms-list mailing list
>GDA...@li...
>http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list
>
>
--------------------------------------
Charles Bloom           www.cbloom.com

Ok, when I said *desired polys* I was thinking on fewer polys, but it can
cause object to collide with nothing (aka air...). I'm not sure what you
want to say with using OBB's... divide the VIPMesh in subchunks and make a
tree of OBB's to quickly skip parts of the model?

Charles Bloom wrote:

> Or, even better, using a static version of the mesh with *fewer*
> polys.  Better still, use a sphere-tree or OBB-tree fit to
> the mesh with roughly 100 spheres and/or OBB's.
>
> At 12:24 AM 8/4/2000 +0200, you wrote:
> >Hi,
> >
> >How can be done fast collision detection with VIPM when it's always
> >changing its morphology?, using an static version of the mesh with all
> >desired polys?
> >
> >
> >_______________________________________________
> >GDAlgorithms-list mailing list
> >GDA...@li...
> >http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list
> >
> >
> --------------------------------------
> Charles Bloom           www.cbloom.com
>
> _______________________________________________
> GDAlgorithms-list mailing list
> GDA...@li...
> http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list

The OBB tree is used for coarse collision detection - a single OBB may even
be enough, depending on the shape of your object ... it depends what form of
collision detection you need - do you need polygon level or just rough OBB ?

Perhaps you could maintain a convex hull generated from the VIPM mesh every
so often, which may be good enough for your needs ?  I believe Stan Melax
has done some work on dynamic reduction of the convex hull too ... check out
his site (sorry, don't have the link at the mo').

Mark

----- Original Message -----
From: "Oscar Blasco" <tr...@te...>
To: <gda...@li...>
Sent: Friday, August 04, 2000 9:06 AM
Subject: Re: [Algorithms] Collisions with VIPM

> Ok, when I said *desired polys* I was thinking on fewer polys, but it can
> cause object to collide with nothing (aka air...). I'm not sure what you
> want to say with using OBB's... divide the VIPMesh in subchunks and make a
> tree of OBB's to quickly skip parts of the model?
>
> Charles Bloom wrote:
>
> > Or, even better, using a static version of the mesh with *fewer*
> > polys.  Better still, use a sphere-tree or OBB-tree fit to
> > the mesh with roughly 100 spheres and/or OBB's.
> >
> > At 12:24 AM 8/4/2000 +0200, you wrote:
> > >Hi,
> > >
> > >How can be done fast collision detection with VIPM when it's always
> > >changing its morphology?, using an static version of the mesh with all
> > >desired polys?
> > >
> > >
> > >_______________________________________________
> > >GDAlgorithms-list mailing list
> > >GDA...@li...
> > >http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list
> > >
> > >
> > --------------------------------------
> > Charles Bloom           www.cbloom.com
> >
> > _______________________________________________
> > GDAlgorithms-list mailing list
> > GDA...@li...
> > http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list
>
>
> _______________________________________________
> GDAlgorithms-list mailing list
> GDA...@li...
> http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list

I'm thinking on terrain and level (map) collision, not in small objects
collision, something I will do with an octree for static and non-static object
(for moving ones I may try another stratregy...). The hardest part is terrain
collision, we can subdivide our terrain in chunks but if they have many polys,
it isn't a good idea to use the current mesh directly. At the moment, I only can
imagine to use a mesh with fewer polys and skip chunks that can be touched using
an octree and portals (these two things can be used to fast visibility skips )
but this can fail in some specific tasks. I ask if there's another way to do
this....

Mark Wayland wrote:

> The OBB tree is used for coarse collision detection - a single OBB may even
> be enough, depending on the shape of your object ... it depends what form of
> collision detection you need - do you need polygon level or just rough OBB ?
>
> Perhaps you could maintain a convex hull generated from the VIPM mesh every
> so often, which may be good enough for your needs ?  I believe Stan Melax
> has done some work on dynamic reduction of the convex hull too ... check out
> his site (sorry, don't have the link at the mo').
>
> Mark
>
> ----- Original Message -----
> From: "Oscar Blasco" <tr...@te...>
> To: <gda...@li...>
> Sent: Friday, August 04, 2000 9:06 AM
> Subject: Re: [Algorithms] Collisions with VIPM
>
> > Ok, when I said *desired polys* I was thinking on fewer polys, but it can
> > cause object to collide with nothing (aka air...). I'm not sure what you
> > want to say with using OBB's... divide the VIPMesh in subchunks and make a
> > tree of OBB's to quickly skip parts of the model?
> >
> > Charles Bloom wrote:
> >
> > > Or, even better, using a static version of the mesh with *fewer*
> > > polys.  Better still, use a sphere-tree or OBB-tree fit to
> > > the mesh with roughly 100 spheres and/or OBB's.
> > >
> > > At 12:24 AM 8/4/2000 +0200, you wrote:
> > > >Hi,
> > > >
> > > >How can be done fast collision detection with VIPM when it's always
> > > >changing its morphology?, using an static version of the mesh with all
> > > >desired polys?
> > > >
> > > >
> > > >_______________________________________________
> > > >GDAlgorithms-list mailing list
> > > >GDA...@li...
> > > >http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list
> > > >
> > > >
> > > --------------------------------------
> > > Charles Bloom           www.cbloom.com
> > >
> > > _______________________________________________
> > > GDAlgorithms-list mailing list
> > > GDA...@li...
> > > http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list
> >
> >
> > _______________________________________________
> > GDAlgorithms-list mailing list
> > GDA...@li...
> > http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list
>
> _______________________________________________
> GDAlgorithms-list mailing list
> GDA...@li...
> http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list