Forza Horizon 5 ships on PC, Xbox Series X and Series S with hardware-accelerated ray tracing support to embellish vehicle reflections - but only in Forza Vista and garage modes. This is something of a shame, especially when photo mode in particular stands to benefit immensely. However, on the DF Supporter Program, one of our backers - Frosticles - produced an RT mod for the PC version (with an assist from Rotab for the Windows Store version), allowing for reflections to run in all modes of the game. So, how beneficial is it and what is the performance cost? Could it be enabled in future on Xbox Series X?
To begin with, let's clarify how standard reflections work in Forza Horizon 5, because it's fair to say that even without RT, they look great. If you can imagine six invisible cameras attached to the player vehicle, capturing imagery and mapping it onto a sphere, you get some idea of how the reflections are generated. Effectively, you're looking at cube-map reflections generated continuously in real-time. These reflections are not perspective-correct, but it's close enough and works well enough.
Hardware accelerated ray tracing further embellishes effect by adding RT reflections of the vehicle onto the car itself, something the cube-maps can't do. It's important to stress that it is only the car - not the environment - being traced and certainly not other cars. Anything outside of the player vehicle that makes its way into FH5's reflections all comes from that real-time cube-map image. The specific way that the reflections work also means that 'reflections within reflections' are possible - so wing mirrors reflected in the door glass 'work', though in this case, it's the cube-map from the mirror that is being reflected.