[ODE] sphere-mesh and box-mesh crash

[Patrick Enoch]

Hello,

Collider.GetNbTouchedPrimitives() will return the number of triangles  
in the container allright.
however, i think that Collider.GetContactStatus() will make sure the  
triangles are valid.

GetContactStatus will check the OPCODE flags against "collision  
occured", which i think
is necessary for valid entries in the container.

Patrick


On 25. Jun 2005, at 15:01 Uhr, Adam D. Moss wrote:

> Patrick Enoch wrote:
>
>> I experienced crashes. The container with the touched primitives  
>> was  supposedly filled with a lot of
>> triangles. when checking the triangles, I saw there were indices  
>> like  "0xC0BA1234" and so on... this
>> certainly causing to crash "FetchTriangle" in the following code...
>> when testing for the status I saw that the status said "no   
>> collisions", thus the indices are bogus.
>>
>
> If Collider.GetNbTouchedPrimitives()==0 then AFAICS we never execute
> the FetchTriangle path, so is GetNbTouchedPrimitives()'s return  
> actually
> bogus if we didn't collide?
>
> In either case, Collider.GetContactStatus() looks like a cheap  
> function
> so it doesn't hurt to be protective, but it'd be better if we were
> sure we weren't wallpapering over a different bug.  We might well just
> be using OPCODE wrongly (i.e. GetNbTouchedPrimitives only works if
> there was a collision).
>
> Does this patch look okay?  It tests okay.  I'll apply it to the trunk
> shortly, if so.
>
> --adam
> Index: ode/src/collision_trimesh_box.cpp
> ===================================================================
> --- ode/src/collision_trimesh_box.cpp    (revision 4638)
> +++ ode/src/collision_trimesh_box.cpp    (working copy)
> @@ -1203,6 +1203,11 @@
>          Collider.Collide(dxTriMesh::defaultBoxCache, Box, TriMesh- 
> >Data->BVTree, null,
>                           &MakeMatrix(vPosMesh, mRotMesh, amatrix));
>      }
> +
> +  if (!Collider.GetContactStatus()) {
> +     /* no collision occurred */
> +     return 0;
> +  }
>
>    // Retrieve data
>    int TriCount = Collider.GetNbTouchedPrimitives();
> Index: ode/src/collision_trimesh_ccylinder.cpp
> ===================================================================
> --- ode/src/collision_trimesh_ccylinder.cpp    (revision 4638)
> +++ ode/src/collision_trimesh_ccylinder.cpp    (working copy)
> @@ -958,6 +958,11 @@
>           Collider.Collide(dxTriMesh::defaultBoxCache,  
> obbCCylinder, TriMesh->Data->BVTree, null,&MeshMatrix);
>       }
>
> +         if (!Collider.GetContactStatus()) {
> +            /* no collision occurred */
> +            return 0;
> +         }
> +
>       // Retrieve data
>       int TriCount = Collider.GetNbTouchedPrimitives();
>       const int* Triangles = (const int*) 
> Collider.GetTouchedPrimitives();
> Index: ode/src/collision_trimesh_sphere.cpp
> ===================================================================
> --- ode/src/collision_trimesh_sphere.cpp    (revision 4638)
> +++ ode/src/collision_trimesh_sphere.cpp    (working copy)
> @@ -305,6 +305,11 @@
>                           &MakeMatrix(TLPosition, TLRotation,  
> amatrix));
>       }
>
> +        if (!Collider.GetContactStatus()) {
> +            /* no collision occurred */
> +            return 0;
> +        }
> +
>      // get results
>      int TriCount = Collider.GetNbTouchedPrimitives();
>      const int* Triangles = (const int*) 
> Collider.GetTouchedPrimitives();
>