[ODE] Collisions from models

[Ivan Bolcina]

In direct3d, I build hierarcy of boxes. I do this with 
D3DXLoadMeshHierarchyFromX function and as a result,  I get array of 
boxes. I had trouble at first because boxes have their own transform. So 
I had to mutiply those transforms to get the final one. Once you have 
array of boxes, it is easy, something like "if (bounding=="boxes") ...." 
code. I was using axis-aligned boxes, but this is not necessary. So I 
think ordering is only important because of  tranformation matrixes.


David Rogers wrote:

> Hey, thanks.  that helps a little bit.  Unfortunately I'm not using 
> directx.  Good ol' opengl with lib3ds(from sourceforge) to load and 
> display the models.
>
> From lib3ds, once a file is loaded, the structure that contains the 
> models data does have an array of the meshes.  I assume then that the 
> process would be similar.  Am I right?  I'm not sure how the meshes 
> are ordered in the array yet(haven't looked at it that much), but 
> would that matter?
>
> thanks,
>
> dave
>
> On May 18, 2004, at 4:21 AM, Ivan Bolcina wrote:
>
>> David Rogers wrote:
>>
>>> Hi all, I'm new to ODE and I haven't found any examples yet of how 
>>> to do what I want.  I have some 3DS models that I load for a game 
>>> and I'm trying to use ODE for collision detection between the 
>>> models.  Does anyone have an example or pointers to info on how to 
>>> go about building the bboxes or whatever i need?
>>>
>>> thanks in advance,
>>>
>>> dave rogers
>>>
>>> _______________________________________________
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>>> ODE at q12.org
>>> http://q12.org/mailman/listinfo/ode
>>>
>> Hi.
>> You can use following pattern.
>>
>> 1. Convert 3ds  model to .x model.
>> 2. Load .x model into hierarcy - D3DXLoadMeshHierarchyFromX
>> 3. this way you can get array of boxes. You can construct ODE body 
>> from it.
>>
>>  void SObject::createPhy()
>> {
>>    if (PhyUp) return;
>>    PhyUp=true;
>>    string bounding=entry->collision->GetBounding();
>>    D3DXVECTOR3 box=entry->mesh->MainBox.b-entry->mesh->MainBox.a;
>>    if (bounding=="") bounding="sphere";
>>    if (bounding=="box")
>>    {
>>        PhyBody = dBodyCreate (app->world);
>>        dBodySetGravityMode(PhyBody,1);
>>        dBodySetPosition 
>> (PhyBody,m_Position.x,m_Position.y,m_Position.z);
>>        float vol=box.z*box.y*box.x;
>>        float den=Mass/vol;
>>        dMassSetBox (&m,den,box.z,box.y,box.x);
>>        dBodySetMass (PhyBody,&m);
>>        PhyGeom[0] = dCreateBox (app->space,box.x,box.y,box.z);
>>        PhyGeomCnt=1;
>>        dGeomSetBody (PhyGeom[0],PhyBody);
>>    }
>>    if (bounding=="boxes")
>>    {
>>        PhyBody = dBodyCreate (app->world);
>>        dBodySetGravityMode(PhyBody,1);
>>        dBodySetPosition 
>> (PhyBody,m_Position.x,m_Position.y,m_Position.z);
>>        float vol=box.z*box.y*box.x;
>>        float den=Mass/vol;
>>        dMassSetBox (&m,den,box.z,box.y,box.x);
>>        dBodySetMass (PhyBody,&m);
>>        for (unsigned int i=0;i<entry->mesh->Boxes.size();i++)
>>        {
>>            D3DXVECTOR3 kot1=entry->mesh->Boxes[i].a;
>>            D3DXVECTOR3 kot2=entry->mesh->Boxes[i].b;
>>            D3DXVECTOR3 mid=(kot1+kot2)*0.5f;
>>            D3DXVECTOR3 diff=(kot2-kot1);
>>            dGeomID skatlica=dCreateBox(0,diff.x,diff.y,diff.z);
>>            dGeomID skatlicaonpos=dCreateGeomTransform(app->space);
>>            dGeomTransformSetGeom(skatlicaonpos,skatlica);
>>            dGeomSetPosition(skatlica,mid.x,mid.y,mid.z);
>>            dGeomTransformSetCleanup(skatlicaonpos,1);
>>            dGeomSetBody(skatlicaonpos,PhyBody);
>>            PhyGeom[i]=skatlicaonpos;
>>        }
>>        PhyGeomCnt=(int) entry->mesh->Boxes.size();
>>    }
>>    if (bounding=="sphere")
>>    {
>>        PhyBody = dBodyCreate (app->world);
>>        dBodySetGravityMode(PhyBody,1);
>>        dBodySetPosition 
>> (PhyBody,m_Position.x,m_Position.y,m_Position.z);
>>        float rad=GetRadius();
>>        float vol=rad*rad*rad*3.1459f;
>>        float den=Mass/vol;
>>        dMassSetSphere (&m,den,rad);
>>        dBodySetMass (PhyBody,&m);
>>        PhyGeom[0] = dCreateSphere(app->space,rad);
>>        PhyGeomCnt=1;
>>        dGeomSetBody (PhyGeom[0],PhyBody);
>>    }
>> }
>>
>>
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>
>
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