Comment by pixelpoet

As a lover of ray/path tracing I'm obligated to point out: rasterisation gets its efficiency by amortising the cost of per-triangle setup over many pixels. This more or less forces you to do fixed-resolution rendering; it's very efficient at this, which is why even today with hardware RT, rasterisation remains the fastest and most power-efficient way to do visibility processing (under certain conditions). However, this efficiency starts to drop off as soon as you want to do things like stencil reflections, and especially shadow maps, to say nothing of global illumination.

While there are some recent'ish extensions to do variable-rate shading in rasterisation[0], this isn't variable-rate visibility determination (well, you can do stochastic rasterisation[1], but it's not implemented in hardware), and with ray tracing you can do as fine-grained distribution of rays as you like.

TL;DR for foveated rendering, ray tracing is the efficiency king, not rasterisation. But don't worry, ray tracing will eventually replace all rasterisation anyway :)

[0] https://developer.nvidia.com/vrworks/graphics/variableratesh...

[1] https://research.nvidia.com/sites/default/files/pubs/2010-06...