[MSL] Metal Multi-View Rendering

[bluesky013]

When converting to MSL with multiview enabled, should amplification_id be used instead of layer rendering?

https://developer.apple.com/documentation/metal/render_passes/improving_rendering_performance_with_vertex_amplification?language=objc

[cdavis5e]

I actually wanted to do this when I implemented multiview. The problem is that, at least at the time, vertex amplification only supported two views, and VK_KHR_multiview requires a minimum of six, so we'd still need to do some emulation, even with vertex amplification. One day, I'd like to go back to this and implement support for vertex amplification, but patches are always welcome.

[bluesky013]

Thank you for your reply. According to the latest metal feature table, for chips above A14, the Maximum vertex count for vertex amplification can support up to 8.

If converted to layer rendering, it might pose challenges when handling different APIs such as Vulkan and Metal in the engine pipeline. This is because the biggest advantage of using MultiView is that it does not have a large impact on the organization of drawcalls in the pipeline, including cases where instancing/indirect usage exists.

[HansKristian-Work]

I guess whoever needs this should make a PR.