[ODE] 2 more quick ODE newbie questions.

Jon Watte (ODE) hplus-ode at mindcontrol.org
Tue Aug 28 08:08:20 MST 2007

It's usually a good idea to create a space encompassing each entity, if 
that entity has some number of bodies. I wouldn't necessarily bother for 
an entity with two bodies, but I would for an entity with ten. If you 
create a general framework that does it for all entities, that's simpler.

In general, performance on modern machines is so good that you can get 
away with all kinds of inefficiencies and not notice, until you try to 
push it to the max, which you very seldom actually need to do.


          / h+

Jeremy Roberts wrote:
> Hello,
>      I have 2 more quick questions from an ODE newbie.
>      1)  I am trying to figure out exactly what data needs to be 
> stored in object instances that use ODE.  For all intents and purposes 
> I would like to simply be able to store the dBodyID.  Then, 
> during instance destruction call something like 
> dBodyDestroyGeoms(dBodyId) and dBodyDestroyJoints(dBodyId).  Therefore 
> an object instance would only require storage of a single ID (the 
> dBodyId).  The destruction pipeline seems a little un-user intuitive.  
> Does one really have to store ALL geomsIDs, all JointIDs and all 
> dBodyIDs for any given object instance?  If this has been covered 
> somewhere I apologize.  I am new to using ODE. 
>      2) I know to create spaces encompassing objects with multiple to 
> many geoms but am still curious how important it is to create a 
> hierarchy of spaces for a mid sized outdoorsy game.  Is the quad-tree 
> enough? 
>      Thank you for your help.
>      Jeremy (grill8)
>     ----- Original Message -----
>     *From:* Jeremy Roberts <mailto:jroberts at digipen.edu>
>     *To:* ODE at ode.org <mailto:ODE at ode.org>
>     *Sent:* Monday, August 27, 2007 7:44 PM
>     *Subject:* New to ODE (a few more basic questions).
>     Hello,
>          Thanks to all who responded to my previous post.
>     To all -
>          I am new to ODE and have a few more basic questions.  I am
>     trying to figure out an effective pipeline for generation of ODE
>     data and would love to hear input if there is a more effective
>     pipeline than the one I outline below.
>          The steps I am thinking of using to create physics data for
>     my 3D app are as follows.
>          1) Use a modeler (in my case Milkshape) to create meshes that
>     correspond to the geom/space hierarchy associated with the object.
>          2) Create a .x file and hard code that information generated
>     from the modeler radii / extents / rotations / positions etc. in
>     the file.  Also hard code the mass/inertia matrices etc.
>          3) When an object is loaded, parse the associated .x file and
>     read the associated physics traits.
>          4) Insert them into a globally initialized quad space.
>     Other questions:
>          1) Is there a way to create the geoms directly from the
>     meshes generated in the modeler?  As far as I know DirectX only
>     can create AABBs and Spheres.  I do not know of a way to create
>     non-AABBs or cylinders directly from DirectX meshes hence the need
>     to hard code that data in the file.  The mass/inertia matrices
>     would need to be hard coded regardless.
>          2) For an outdoors 3D app is there a need to create a space
>     hierarchy (other than the one for each object) besides the Quad Tree?
>     Thank you for your help.
>     Jeremy
>     A.S. Real Time Interactive Simulation
>     [Video Game Computer Science]
>     DigiPen Institute of Technology
>     - Make the world what it could be, not what it is.
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