Re: [ODE] I´m totally unhappy with ODE ... Please Help me

arturapps arturapps at
Fri Dec 15 18:08:43 MST 2006

when I do collision detection , I hope to get colision points as a result of
the last movements .( the IA did the movements) . 
In fact I'm not using the colision points yet. I'm monitoring the return of
dCollide inside the near callback. 

Most of my problems are: I can see the colision  , but dCollide returns 0. 

sometimes I see the colision but callback is not triggered. 

By now I really must know if is it correct to use only colision detection
from ODE engine , without using physics .

Pierre-Laurent CHAMBERT wrote:
> Hi Artur!
> Maybe the problems simply comes from the main loop order :
> you do collision detecion, and then draw the scene without handling 
> collision points. So this way it's possible that some objects are 
> colliding, and drawn like that.
> what you should do is :
> collision detecion
> handle it (with IA as far as I understand)
> and then draw the scene.
> (or just swap collision detection and rendering in your current loop).
> I think this should remove your troubles.
> Pilo
> arturapps a écrit :
>> Hi people: 
>> I´m working on a game that doesn´t need Real time physics  but needs
>> Trimesh-Trimesh colision Detection . 
>> The game is a kind  of spaceship race that takes place on a  quite large
>> enviromment composed of trimeshes.
>> I´m  experiencing all kind of problems with my collisions : Since false
>> collisions , until  missed collisions. Sometimes  the near callback is
>> not
>> triggered even if two trimeshes visually collide.
>> I examined ODE´s documentation and figured out that  it´s possible to use
>> just the colision detection capabilitys of ODE.  So my sojtware does not
>> create the "word"  and any body   for physics  processing. The ODE´s
>> "step"
>> of simulation is not called.  The software just create the colision space 
>> and associate   geoms ( trimeshes ) to  the game entitys . 
>> That´s the way the game works: 
>> Create collision space
>> Create Entytys and associated geoms ( trimeshes) 
>> (Loop) 
>> {
>> Call Entity´s IA  // Each entity decide about its next movement and then
>> modify it´s position and  orientation
>> modify entity´s geoms // based on entity´s  position and orientation
>> call colision detection (dSpaceCollide) 
>> Draw 
>> }
>> (nearCallback) 
>> {
>>  call dcollide  to get contact points between the colision pair
>> iinform the entitys associated with the colision geoms , about the
>> colision
>> points 
>> //In the next loop the Entity´s IA will do something as colision response
>> }
>> Well ... first of all , I´d like to know if is that aproach correct. IS
>> there any problem using just colilision detection system  of ode ?
>> By the way : I´m using  the version of ODE , that uses GIMPACT instead of
>> OPCODE. I downloaded  this version at :
>> In second place : I´d like to describe some tests I made to be sure that
>> my
>> trimeshes and trimesh creation process are correct: 
>> I  changed the test_moving_trimesh example that comes with the 
>> ODE-Gimpact
>> project, in order to create the trimeshes from my model file format ,
>> instead of creating the "bunnys" on the code.  I didn´t changed the way
>> it
>> does trimesh creation because it was the same way I do it . So I could
>> notice that my trimesh models work very well . they are displayed
>> correctly
>> and collyde very well.  So I discarded problems about vertex order or
>> normal
>> orientation. 
>> In my software I don´t call dGeomTriMeshSetLastTransform in order to
>> update
>> temporal coerence for the Geoms. 
>> I removed all calls of  dGeomTriMeshSetLastTransform from the
>> test_moving_trimesh example  and than I noticed that it does not afect
>> colisions , but only the quality of physics simulation. 
>> So I don´t know what I can do next  in order to understand my problem ? 
>> Help me please !!!
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