Except the illusion is strong enough to work in many cases. And as with much of computing, faking it is enough. 3d graphics has been built on that since day one

Except the illusion is strong enough to work in many cases. And as with much of computing, faking it is enough. 3d graphics has been built on that since day one and only recently have we had ray tracing and other more “realistic” to nature techniques generally available.