Forza Horizon 5 on PC, a mod adds Ray Tracing: here's how it improves the graphics

Forza Horizon 5 on PC, a mod adds Ray Tracing

Forza Horizon 5 has arrived on PC, Xbox Series X and Series S with hardware accelerated ray tracing support to beautify car reflections, but only in Forza Vista and in the garage. This is really a shame, especially as the photo mode in particular benefits enormously from it. But in the DF Support Program, one of the donors - Frosticles - has produced an RT mod for the PC version (with the assistance of Rotab for the Windows Store version), which extends RT reflexes to the whole game, including the open world. . So how does it improve the visual impact? And how much does it cost in terms of performance? Could it be enabled on Xbox Series X in the future?

To begin with, we need to explain how standard reflexes work in Forza Horizon 5, because it has to be said that even without RT they look gorgeous. If you could imagine six invisible cameras attached to the player's vehicle, capturing images by mapping them into a sphere, then you could get an idea of ​​how these reflections are made. Actually these are cube-map reflections generated continuously in real time. These reflections aren't perspective accurate, but they come close enough and make a good impression.

Here's what Forza Horizon 5 looks like with ray tracing applied to all areas of the game, and the cost of performance required to do so.

Watch on YouTube. Hardware-accelerated ray tracing further beautifies the effect by adding vehicle RT reflections to the car itself, something cube-maps are unable to do. However, it must be emphasized that this is only the user's car, so there are no RT reflections applied to other cars, much less the environment. All the other elements that generate reflections are in fact managed with standard cube-maps. The very way that reflections work implies that it is possible to generate "reflections in reflections", so the side mirrors come in the windows, although in this case it is the cube-map reflection of the mirror that is reflected.

In many scenarios the change is minimal, especially while driving at speed, but approaching the car the difference can be striking, so using this mod in photo mode is of great benefit in generating great shots. In fact, the thumbnail of our attached video (and the cover image on the front page) are based on the press material provided to us by Playground Games, and are made with RT enabled. In fact, you can see the vehicle reflected in the headlights of the car. And even the pre-rendered intro footage is handled with the same effect. Cars are ultimately center stage in this game, and hardware-accelerated ray tracing emphasizes model quality even more.

In our original technical review we weren't very happy with the scalability of the PC version in moving beyond the quality profile of the Xbox Series X, but activating the RT offers a distinct upgrade, even if it has limitations. For one thing, the car is only viewed from the rear and this implies that the impact of reflections varies a lot according to the design of the model. Also, the RT hardware does not work inside vehicles, so for example the rearview mirror does not reflect the interior of the car. And the last limit is that only the details of the user's car are reflected, the driver's model is never reflected. This is in some ways a shame considering the potential it would have in photo mode or the actual game, but it wouldn't have sanctioned any difference in the utility of Forza Vista or the garage.

The ray tracing mod enables ray traced auto-reflections. Self-reflections can significantly improve the realism of car sheets and glass. The mod also allows you to change the resolution / ray-per-pixel ratio of reflections. The mod also allows you to change the bounce reflections, which especially help with self-reflecting shadows. However, in addition to forcing the RT in all areas of the game, the mod also accesses other parameters. The ray-per-pixel or reflection settings can be changed to increase the fidelity of the reflections. A radius per pixel gives a good result, but going beyond this number helps to eliminate aliasing from reflections and therefore increases the quality, obviously decreasing the performance. Another option is to increase the number of times the rays bounce, and here too the qualitative result is visible. Changing all these parameters is fascinating and gives us an idea of ​​the scalability and customization possibilities of the system designed by Playground Games, which obviously is a technology in progress.

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Let's say you have FH5 on PC and want to try this mod: what is its cost in terms of performance? First of all, of course you must have suitable graphics hardware (Nvidia RTX with Turing or Ampere architecture or AMD RDNA 2). That said, the performance cost depends on the GPU you own, the rendering resolution and how close you get to the car. For our tests we chose the RTX 3080 and RX 6800 XT as Nvidia and AMD respectively, and used the 4K resolution benchmark.

On the Nvidia side, RT reflections add 1.7 ms to the render time compared to the default configuration. On the AMD side, the additional time is about 2.9 ms. In the 60fps calculation, we aim for 16.7 ms of available time as the maximum, so it is evident that the request for render time for this type of RT is high, so keeping the 4K60 is more sustainable on the RTX 3080.

Could this game-wide RT be implemented on Xbox Series X? Considering that the RX 6800 XT is much more powerful than Microsoft's flagship console GPU, that extra 2.9 ms of rendering would go up noticeably, making the frame-rate too low. So maybe it wouldn't be possible. But PC gaming is all about options fired to the max to achieve the highest possible fidelity, so we hope that at least if this platform the developer decides to officially implement this feature.

The mod seems to work very well: the only problem we encountered concerns the visible artifacts on the rear window of a single car. At the moment it is clear that we are at the beginning of RT in ForzaTech, but we are curious to find out how this technology will evolve for the upcoming Forza Motorsport.