should btTriangleMesh for 3ds file for terrain??

[fishfish]

I have a prog. that can import 3ds file for terrain.

Should I use btTriangleMesh for collision detection?

Thanks in advance.

[Erwin Coumans]

Yes, you can create a btTriangleMesh and add all triangles to this container. Then pass this mesh interface to btBvhTriangleMeshShape. Note that you can still use compression/quantization for the Bvh tree, the comment in the code is obsolete (is updated for next version). See Demos\UserCollisionAlgorithm\UserCollisionAlgorithm.cpp for an example:

Code: Select all

	btTriangleMesh* trimesh = new btTriangleMesh();

	for ( i=0;i<NUM_VERTS_X-1;i++)
	{
		for (int j=0;j<NUM_VERTS_Y-1;j++)
		{
			trimesh->addTriangle(gVertices[j*NUM_VERTS_X+i],gVertices[j*NUM_VERTS_X+i+1],gVertices[(j+1)*NUM_VERTS_X+i+1]);
			trimesh->addTriangle(gVertices[j*NUM_VERTS_X+i],gVertices[(j+1)*NUM_VERTS_X+i+1],gVertices[(j+1)*NUM_VERTS_X+i]);
		}
	}
	
	delete[] gVertices;

	bool useQuantizedBvhTree = true;
	btCollisionShape* trimeshShape  = new btBvhTriangleMeshShape(trimesh,useQuantizedBvhTree);
		

Instead of duplicating the mesh data, you can also reference existing vertices/indices in-memory, using btTriangleIndexVertexArray. See ConcaveDemo for an example:

Code: Select all

	btTriangleIndexVertexArray* indexVertexArrays = new btTriangleIndexVertexArray(totalTriangles,
		gIndices,
		indexStride,
		totalVerts,(btScalar*) &gVertices[0].x(),vertStride);

	bool useQuantizedAabbCompression = true;
	trimeshShape  = new btBvhTriangleMeshShape(indexVertexArrays,useQuantizedAabbCompression);

Hope this helps,
Erwin

[fishfish]

Thx a lot

Yes, you can create a btTriangleMesh and add all triangles to this container. Then pass this mesh interface to btBvhTriangleMeshShape. Note that you can still use compression/quantization for the Bvh tree, the comment in the code is obsolete (is updated for next version). See Demos\UserCollisionAlgorithm\UserCollisionAlgorithm.cpp for an example:

Code: Select all

	btTriangleMesh* trimesh = new btTriangleMesh();

	for ( i=0;i<NUM_VERTS_X-1;i++)
	{
		for (int j=0;j<NUM_VERTS_Y-1;j++)
		{
			trimesh->addTriangle(gVertices[j*NUM_VERTS_X+i],gVertices[j*NUM_VERTS_X+i+1],gVertices[(j+1)*NUM_VERTS_X+i+1]);
			trimesh->addTriangle(gVertices[j*NUM_VERTS_X+i],gVertices[(j+1)*NUM_VERTS_X+i+1],gVertices[(j+1)*NUM_VERTS_X+i]);
		}
	}
	
	delete[] gVertices;

	bool useQuantizedBvhTree = true;
	btCollisionShape* trimeshShape  = new btBvhTriangleMeshShape(trimesh,useQuantizedBvhTree);
		

Instead of duplicating the mesh data, you can also reference existing vertices/indices in-memory, using btTriangleIndexVertexArray. See ConcaveDemo for an example:

Code: Select all

	btTriangleIndexVertexArray* indexVertexArrays = new btTriangleIndexVertexArray(totalTriangles,
		gIndices,
		indexStride,
		totalVerts,(btScalar*) &gVertices[0].x(),vertStride);

	bool useQuantizedAabbCompression = true;
	trimeshShape  = new btBvhTriangleMeshShape(indexVertexArrays,useQuantizedAabbCompression);

Hope this helps,
Erwin

[Bruno Duarte]

I just don't understand a thing.

This method implement a way to create the mesh collision, but how can i assign my 3ds model to this collision mesh ?


And another question, all the vertices must be in a vector off one dimension, i mean,does all of then must be aligned like , vertex1.x then vertex1.y and then vertex1.z, all in line ?

[Bruno Duarte]

Hey ,can we talk bout how to use a 3ds file in bullet ?
i am using it too and i can't understand the part

Code: Select all

addTriangle(gVertices[j*NUM_VERTS_X+i],gVertices[j*NUM_VERTS_X+i+1],gV
ertices[(j+1)*NUM_VERTS_X+i+1]);

the gVertices by the way have the informations about the point as a unidimensional array ? i am using like this

Code: Select all

		int index0 = pObject->pFaces[j].vertIndex[0];
					int index1 = pObject->pFaces[j].vertIndex[1];
					int index2 = pObject->pFaces[j].vertIndex[2];



btVector3 vertex0(pObject->pVerts[index0].x,pObject->pVerts[index0].y,pObject->pVerts[index0].z);
			btVector3 vertex1(pObject->pVerts[index1].x,pObject->pVerts[index1].y,pObject->pVerts[index1].z);
			btVector3 vertex2(pObject->pVerts[index2].x,pObject->pVerts[index2].y,pObject->pVerts[index2].z);
			
			
			
			
			trimesh->addTriangle(vertex0,vertex1,vertex2);

but it's not working, you can tell me what is my mistake





the strange is, when i use

Code: Select all

//convex way************************************************************************
	btCollisionShape* convexShape = new btConvexTriangleMeshShape(trimesh);
		
		
		btTransform startTransform;
		startTransform.setIdentity();
		startTransform.setOrigin(btVector3(0,0,0));

		localCreateRigidBody(0.0f, startTransform,convexShape);
	/****************************************************************/

for convex way, does it works