I think you could do foveated rendering efficiently with rasterization if you "simply" render twice at 2 different resolutions. A low resolution render over the entire FOV, and a higher resolution render in the fovea region. You would have overlap but overall it should be less pixels rendered.

I believe the standard way is to downgrade the sampling density outside the area you're looking, see https://docs.vulkan.org/samples/latest/samples/extensions/fr... . Optimally you could attach multiple buffers with different resolutions covering different parts of clipspace, saving vram bandwidth. Sadly this is not supported currently to my knowledge, so you have to write to a single giant buffer with lower sample resolution outside the detail area, and then just downsample it for the coarse layer.