Slightly Mad clarifies Project Cars AMD performance issues

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Project Cars is one of the most incredible-looking games on the planet right now, but it’s also the subject of a bit of storm-in-a-teacup controversy at the moment, because users have found that AMD’s graphics cards perform sub-optimally with the game, giving gamers who choose AMD far fewer of those treasured eff-pee-essess than those who have equivalent NVidia-based cards. The principal reason, it seems, is that Nvidia’s PhysX technology is baked right in to Project Cars’ Madness engine. It’s led to many wondering if Nvidia isn’t using shady business dealings to games on AMD systems. It’s become a big enough problem that developer Slightly Mad Studios has released a press release to clarify the matter.

Here’s what the press release says:

“There has been a lot of controversy surrounding the performance of Project CARS on AMD’s graphics cards. And this whole thing forced Slightly Mad Studios to issue an official statement about it. As the statement reads, for the past few days, erroneous information posted on Reddit and other websites has spread misinformation with regards to Project CARS’ performance on systems using AMD GPUs.

In order to correct the wrongful assumptions regarding Project CARS’ performance on AMD GPUs, the MADNESS engine and the degree of involvement from our third-party technical partners, Slightly Mad Studios pointed out the following facts:

  • Project CARS is not a GameWorks product. We have a good working relationship with nVidia, as we do with AMD, but we have our own render technology which covers everything we need.
  • NVidia are not “sponsors” of the project. The company has not received, and would not expect, financial assistance from third party hardware companies.
  • The MADNESS engine runs PhysX at only 50Hz and not at 600Hz as mentioned in several articles
  • The MADNESS engine uses PhysX for collision detection and dynamic objects, which is a small part of the overall physics systems
  • The MADNESS engine does not use PhysX for the SETA tyre model or for the chassis constraint solver (our two most expensive physics sub-systems)
  • The MADNESS engine does not use PhysX for the AI systems or for raycasting, we use a bespoke optimised solution for those
  • The physics systems run completely independently of the rendering and main game threads and utilises 2 cores at 600Hz
  • The physics threading does not interact with the rendering, it is a push system sending updated positional information to the render bridge at 600Hz
  • Any performance difference with PhysX would not be reflected with differences in comparing rendering frame rates. There is no interaction between PhysX and the rendering
  • Overall, PhysX uses less than 10% of all physics thread CPU on PC. It is a very small part of the physics system so would not make a visual difference if run on the CPU or GPU
  • Direct involvement with both nVidia and AMD has been fruitful in assisting with the game performance at various stages of development. Both AMD and nVidia have had access to working builds of the game throughout development, and they have both tested builds and reported their results and offered suggestions for performance improvements.
  • Testing of the game with different driver versions has produced a variety of performance results on both nVidia and AMD hardware. This is entirely to be expected as driver changes cannot always be tested on every game and every card, and this is the reason why both companies produce game-specific driver profiles, to ensure that they can get the best out of the game.
  • Project CARS does not use nVidia specific particle technology – the system we use is a modified version of the same technology we used on the Need for Speed : Shift and Shift Unleashed games, and was entirely developed in-house. The reason the performance drops when there are a lot of particles on screen is simply because processing a large number of particles is very expensive.

So hopefully that clears up confusion – but what it doesn’t do is make the game work any better on AMD cards. As we pointed out yesterday, Nvidia’s mid-range GTX 960 outperforms AMD’s higher-end cards in the game, largely thanks to the baked in PhysX implementation, and thanks – according to some – to how the cards handle tessellation.

Whatever the reasons for it, AMD owners are being stiffed – and that’s not okay.

Last Updated: May 19, 2015

Geoffrey Tim

Editor. I'm old, grumpy and more than just a little cynical. One day, I found myself in possession of a NES, and a copy of Super Mario Bros 3. It was that game that made me realise that games were more than just toys to idly while away time - they were capable of being masterpieces. I'm here now, looking for more of those masterpieces.

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