(C++) Making a Newton Convex hull from an IMesh

[Gothi[c]]

This function makes a newton Convex hull from an Irrlicht mesh for collision testing.

requires nWorld global (newton world)
I was too lazy to put it as a function argument but i guess you could do that.

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/////////////////////////////////////////////////////////////////////////////

  struct CollisionMesh
    {
    NewtonCollision* Collision;
    NewtonBody* Body;
    };

/////////////////////////////////////////////////////////////////////////////

  CollisionMesh CreateNewtonCollisionConvex(IAnimatedMesh *Mesh)
    {

    // get a mesh from the animated mesh. (default first frame)

    IMesh* MyMesh = Mesh->getMesh(0);

    // Init stuff

    int BufferCount = MyMesh->getMeshBufferCount();
    IMeshBuffer* mb = 0;
    NewtonBody* Body;
    NewtonCollision* Collision;
    float *varray = 0;

    // Loop through all vertices and add them to an array of float that newton wants.

    for (int bi = 0 ; bi < BufferCount ; bi++)
      {
      mb = MyMesh->getMeshBuffer(bi);
      int VerticleCount = mb->getVertexCount();
      debugout << "VertexCount : " << VerticleCount;
      varray = new float[VerticleCount*3];
      switch(mb->getVertexType())
        {
        case EVT_STANDARD:
          {
          S3DVertex* Vertices = (S3DVertex*)mb->getVertices();
          for (int ii = 0 ; ii < VerticleCount ; ii++)
            {
            varray[(ii*3)] = Vertices[ii].Pos.X;
            varray[(ii*3)+1] = Vertices[ii].Pos.Y;
            varray[(ii*3)+2] = Vertices[ii].Pos.Z;
            }
            break;
          }
        case EVT_2TCOORDS:
          {
          S3DVertex2TCoords* Vertices = (S3DVertex2TCoords*)mb->getVertices();
          for (int ii = 0 ; ii < VerticleCount ; ii++)
            {
            varray[(ii*3)] = Vertices[ii].Pos.X;
            varray[(ii*3)+1] = Vertices[ii].Pos.Y;
            varray[(ii*3)+2] = Vertices[ii].Pos.Z;
            }
            break;
          }
        }
      }

    // Finalize and return result.

    Collision = NewtonCreateConvexHull(nWorld,mb->getVertexCount(),(float*)varray,(sizeof(float)*3),NULL);
    delete varray;
    Body = NewtonCreateBody(nWorld,Collision);
    CollisionMesh result;
    result.Collision = Collision;
    result.Body = Body;
    return result;
    }

[Baal Cadar]

Useful indeed.
But the function doesn't work for meshes with multiple mesh buffers. You could first determine the accumulated vertex count over all mesh buffers, then create the array and then fill it. As it stands, it only creates the convex hull from the last buffer and has a gaping memory leak with varray newed all over in the for-loop, but not being deleted. And the delete itself uses the wrong operator. It has to be

Code: Select all

delete [] varray;

Also handling of EVT_TANGENTS is missing.

[Gothi[c]]

But the function doesn't work for meshes with multiple mesh buffers.

Right. to prevent that you have to prevent the array pointer to be overwritten. maybe add another dimension to the array or something. Though your idea sounds better :p

And the delete itself uses the wrong operator.

Nothing like submitting a snipplet for debugging

Also handling of EVT_TANGENTS is missing.

Yeah i forgot to add those. But the general idea should be clear