How does culling work with static batching?

Unity Engine
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1

I understand that with static batching Unity combines meshes that are marked as static and have the same material. According to the documentation, “Unity can still cull meshes individually.”

How exactly is this done and what mesh information is sent to the GPU in scenarios where individual parts of the combined mesh are being culled? Does the GPU still receive the entire vertex and index buffer of the combined mesh? If so, how does the GPU know what parts within the mesh to “skip” and not bother processing at all?

2

Documentation does seem vague on how it works. There’s probably an old Unity blog post that goes into the details somewhere. I’m guessing when a static mesh enters or leaves the view frustum the static batcher rebuilds/merges all the onscreen static meshes. I’d like to assume that it rebuilds the mesh using the GPU to copy all the vertex data.