Last weekend, we showcased the PC port of Playground Games' Forza Horizon 3, running at close to its absolute best at 4K resolution with a silky smooth 60 frames per second. It took an overclocked Core i7 and Nvidia's Titan X Pascal to get the job done, but typically, impressive performance at ultra HD tends to scale down nicely to less capable graphics hardware running at 1080p. However, Forza Horizon 3 appears to be something of an exception.

Reports of inconsistent, stuttering performance are far and wide, even using PC hardware that far outstrips both the CPU and GPU power of the Xbox One, so we went back to the game to see the extent to which the issues could be replicated on our test system. The results are bizarre to say the least - using an Intel Skylake-based system, some of the performance issues and inconsistencies almost defy belief.

Typically, a game that runs flawlessly at 4K on the new Titan X should run perfectly with performance to spare on Nvidia's GTX 1060 - but not Forza Horizon 3, which actually runs significantly more slowly. The GTX 970 - quite possibly the most popular enthusiast-level GPU installed in the most PCs today - shows a huge performance deficit compared to the 1060, but its shortfalls are nowhere near as pronounced as the R9 390 compared to the new RX 480, with a gap often in excess of 20fps (!). Bearing in mind that the R9 390 outperforms the RX 480 in many titles, this differential is remarkable.

The list of WTF-level performance issues just continue to stack up the more hardware we tested: Nvidia's mighty Titan X Pascal cannot run this game smoothly at 1080p on ultra settings with the default 4x MSAA in effect - even though it runs smoothly at 4K with multi-sampling disabled. And this leads us on to the first key revelation in optimising Forza Horizon 3 to run at anything like a smooth 60fps: utilising MSAA simply murders any chance of flawless performance.

We take an extended look at Forza Horizon 3's puzzling performance profile, testing out Titan X Pascal, GTX 1060, RX 480, GTX 970 and R9 390. We also look at how weaker CPUs have issues streaming the game world.

Turning off MSAA removes many of the frequent coughs and splutters the game possesses, but it's far from a cure-all. Frame-rate dips appear to be either background streaming related or purely graphics related. Minimising the latter isn't super-difficult. Dropping shadows and world car detail level from ultra to high claws back a lot of performance, while paring back the reflection settings can improve frame-rate with no real substantial impact on image quality during the heat of gameplay.

This can help to address the more sustained drops to frame-rate, but the fact is that the game still has severe streaming issues that requires sheer CPU brute force to overcome. Our Core i7 6700K overclocked to 4.6GHz and paired with 3000MHz DDR4 appears to power past most of the issues, but swapping out the i7 for a Core i5 6500 3.2GHz - similar in performance terms to a fully overclocked Core i5 2500K based on our previous tests - shows the stuttering issue in full effect.

Adjusting settings to trim back draw distance could help here, but it's a Hobson's Choice of a situation - even on ultra settings, pop-in is noticeable and scaling back the dynamic geometry setting causes the pop-in to occur closer to the player position. Dropping back from ultra textures is also worth experimentation - there's not a great deal to differentiate high and ultra. Even medium looks presentable.

When everything goes right and your PC powers past Forza Horizon 3's performance shortcomings, the end result is simply breathtaking. Here, we're playing the game at 4K, 60fps.

LOD settings on Xbox One appear to be somewhat dynamic, which may explain its excellent consistency level. The PC version does have a dynamic load-levelling system too - just like Forza Motorsport 6 Apex - but the issue here is that at high and ultra settings, MSAA is forced on and you can't turn it off, meaning that stutter is never too far away.

All of which makes it sound as though Forza Horizon 3 is a nuclear disaster of a PC port - but this is not the case. While it is clear that some fairly profound optimisation is required - plus a good deal of driver attention from both Nvidia and AMD - the fact is that a beautiful, smooth experience at full ultra settings and 8x MSAA is relatively easy to attain, even with a slower i5 and GTX 970. However, it involves making a compromise that many PC owners won't be happy with: engaging the 30fps limit.

To its credit, the 30fps cap doesn't just limit frame-rate, it also enforces proper frame-pacing, meaning that each frame persists for 33ms - something we confirmed for both AMD and Nvidia hardware, and absolutely crucial in making what is a relatively low frame-rate for PC gaming actually work out. Combined with the excellent quality motion blur, this is a viable way forward for enjoying the game in its current state.

Xbox One's 30fps experience is still beautifully solid - it's an excellent console racer.

Right now, the bottom line is that while a smooth 60fps is possible, the raw brute force required to get the job done on the higher presets is likely beyond the reach of most mainstream gaming PCs, and that's a shame, because the experience clearly benefits immensely. Disabling MSAA is the first step on the journey to a smoother ride, but even doing that comes with some reservations - Xbox One runs with 4x MSAA and it looks great. Even at 4K, no multi-sampling can lead to some intrusive visual artefacts - especially on pixel break-up on power lines. Obviously, these become more of an issue as you scale down resolution. Quite why MSAA is an issue at all - and why enabling it even causes performance issues at 1080p with the fastest single-chip GPU money can buy - is something of a mystery.

We can't help but think that this game needs some work - enough to warrant perhaps holding fire on a Windows Store purchase. While the issues we've encountered are by turns frustrating and even at times inexplicable, at least we're able to physically play the game. Colleagues at Eurogamer Portugal report that the game instantly crashes whenever a race is started, while Eurogamer Germany tells us that the game crashes every couple of minutes. User reports also show a number of issues relating to basic stability.

Clearly, something needs to be done - and hopefully it will be, because when this game is running smoothly at 60fps with all the dials turned up to the maximum, the end result is simply glorious. Resolution, frame-rate, effects and art quality all scale beautifully to provide a premium, top-tier experience. But it shouldn't require a stupendously expensive rig to get the job done - fingers crossed that Playground Games is taking a good, long, hard look at getting Forza Horizon 3 into shape.

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About the author

Richard Leadbetter

Richard Leadbetter

Technology Editor, Digital Foundry

Rich has been a games journalist since the days of 16-bit and specialises in technical analysis. He's commonly known around Eurogamer as the Blacksmith of the Future.

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