Bug SubMeshDescriptor.baseVertex doesn't seem to work.

Hi!

I've got a triangles and a vertices array, result of combining multiple meshes together. I want to then extract one mesh from these uber-arrays, so I'm using SubMeshDescriptor.baseVertex with a negative value to offset the indices in the triangles array.

Thing is, despite the extracted mesh having correct triangle indices, I get this error:

This is the code I'm using:

Code (CSharp):

1.  
2. mesh.SetVertexBufferParams(vCount, vertexLayout);
3. mesh.SetIndexBufferParams(tCount, IndexFormat.UInt32);
4.  
5. //vOffset and tOffset are offsets into the vertices and triangles uber-arrays, respectively.
6. mesh.SetVertexBufferData(uberVertexArray, vOffset, 0, vCount, 0, MeshUpdateFlags.DontRecalculateBounds | MeshUpdateFlags.DontValidateIndices);
7. mesh.SetIndexBufferData(uberTrianglesArray, tOffset, 0, tCount, MeshUpdateFlags.DontRecalculateBounds | MeshUpdateFlags.DontValidateIndices);
8.                  
9. submeshInfo.baseVertex = -vOffset; //offset indices by amount of leading vertices in the uberVertexArray
10. mesh.SetSubMesh(0, submeshInfo);

I get the impression that SetSubMesh doesn't take into account the baseVertex when asserting that the largest index in the triangles array must be < than the vertexCount. Is this a bug, or am I misunderstanding baseVertex?

 

I think you are understanding baseVertex correctly but it is an unusual use case that you have. Usually, you'd use it for the opposite case, when you have multiple combined meshes with unadjusted index buffers in which case baseVertex would be positive.

I've checked the D3D11 DrawIndexed method and BaseVertexLocation is signed indeed, so I think it is a bug.