在DirectX11中为动态和静态对象使用单独的顶点缓冲区

Question

Are there any benefits of having separate vertex buffers for static and dynamic objects in a DirectX 11 application? My approach is to have the vertices of all objects in a scene stored in the same vertex buffer.

However, I will only have to re-map a small number of objects (1 to 5) of the whole collection (up to 200 objects). The majority of objects are static and will not be transformed in any way. What is the best approach for doing this?

Answer 1

Mapping a big vertex buffer with discard forces the driver to allocate new memory every frame. Up to ~4 frames can be in flight, so there can be 4 copies of that buffer. This can lead to memory overcommitment and stuttering. For example, ATI advises to discard vertex buffers up to 4 mb max ( GCN Performance Tweets ). Besides, every time you will have to needlessly copy static data to a new vertex buffer.

Mapping with no overwrite should work better. It would require to manually manage the memory, so you won't overwrite the data which is in flight. I'm not sure about the performance implications, but for sure this isn't a recommended path.

Best approach would be to simplify driver's work by providing as many hints as possible. Create static vertex buffers with immutable flag, long lived with default flag and dynamic with dynamic flag. See vendor guides like GCN Performance Tweets or Don't Throw it all Away: Efficient Buffer Management for additional details.