btHeightfieldTerrainShape is always flat as a pancake

[Prot]

Hello, everyone. I was wondering if one of you could help me with a small problem I'm having with Bullet.

I have a height field specified as an array of unsigned chars. I'm using that height field to successfully render terrain using my own functions. I also had a bvhTriangleMeshShape for collision, and it was working well, but since there are more than 100000 triangles there was a lot of overhead when creating the shape (due to function calls), so I decided to give the HeightfieldShape a try. However, it doesn't seem to like the data I'm sending it.

I tried everything. All the different modes, real maximum height or just a very high number, I checked the demo, read the tutorial, searched in google, everywhere I go I find that I seem to be doing everything correctly, but still the heightfield does not recognize the data. I can scale it, and I can change it into diamond subdivision mode just fine. My stuff collides with it when it hits it. But it's FLAT.

Code: Select all

		unsigned char* heightfield = new (unsigned char[mapa.getWidth() * mapa.getHeight()]);
		int highest = -999999, j = 0;
		for (i = 0; i < NUM_VERTS_X; i++)
			for (j = 0; j < NUM_VERTS_Z; j++) {
				heightfield[j*NUM_VERTS_X+i] = alturas[(i*NUM_VERTS_Z+j)*3];
				if (heightfield[j*NUM_VERTS_X+i] > highest)
					highest = heightfield[j*NUM_VERTS_X+i];
			}

		btHeightfieldTerrainShape* heightfieldShape = new btHeightfieldTerrainShape(mapa.getWidth(), mapa.getHeight(), heightfield, highest, 1, false, false);
		heightfieldShape->setLocalScaling(btVector3(TRIANGLE_SIZE,0,TRIANGLE_SIZE));
		btCollisionShape* trimeshShape = heightfieldShape;
			
		float mass = 0.f;
		btTransform	startTransform;
		startTransform.setIdentity();
		startTransform.setOrigin(btVector3(0,0,0));

		btRigidBody* staticBody= localCreateRigidBody(mass, startTransform,trimeshShape);

alturas contains the data in an array of unsigned chars straight from a PNG (mapa.getBytes()). mapa is the libpng wrapper, it's written by me but extensively tested and I already checked that "heightfield" does contain the heightfield after the copy cycles anyway.; mapa.getWidth() and mapa.getHeight() return exactly the same values as NUM_VERTS_X and NUM_VERTS_Z.

Any help would be much appreciated.

[Erwin Coumans]

but since there are more than 100000 triangles there was a lot of overhead when creating the shape (due to function calls),

It should be possible to use the btBvhTriangleMeshShape. Are you using the btTriangleMesh? The ::addTriangle is very slow, which will be fixed. Have you tried to use the btTriangleIndexVertexArray instead? Also, you can serialize the BVH to speed up initialization, see Demos/ConcaveDemo.

Not sure what is happening with the btHeightfieldTerrainShape. There is some upcoming patch for btHeightfieldTerrainShape that might resolve the issue.
Which version of Bullet are you using?
Thanks,
Erwin

[Prot]

2.72. It was indeed the addTriangle being incredibly slow. Let me try the vertex array instead...

[Erwin Coumans]

You can try attached zipped btTriangleMesh.cpp, it avoids the slow duplicate vertex search in addTriangle by default.

Still, it is better to use btTriangleIndexVertexArray .
Hope this helps,
Erwin

[Prot]

Thank you, but I already reimplemented with btTriangleIndexVertexArray and it's working perfectly now
I'll keep your example for future reference! Thanks a lot.