Portal with RTX starts a new retro ray tracing revolution

Portal with RTX is an absolute triumph, not only for its masterful use of lighting and cutting-edge technology, but also for how it works – which borders on black magic. This new take on the Valve classic is powered by a new framework from Nvidia called RTX Remix, which essentially hijacks legacy PC games that rely on a fixed function rendering path and replaces rasterization with full path tracing. It even adds motion vectors, opening the door to TAA, DLSS, and even per-object motion blur support.

“Remix” suggests a degree of customization by the user, and that is possible, beautifully presented in Portal. Replacing the rendering allows lights to be overwritten, assets to be swapped out with newly created alternatives, and textures to be created or recreated so that they are physically based. It is a complete system for replacing a game’s graphics with path-tracing that lives entirely outside of the game’s consciousness and gameplay code. It’s honestly amazing that this works at all – and Portal with RTX shows what Remix can do when it takes time to create new assets and adjust every area and asset in a game to work with the new rendering -Paradigm works.

What is the fundamental difference between path tracing and RT in most games? Titles like Cyberpunk 2077 or Marvel’s Spider-Man Remastered still run on rasterization but add RT effects for elements like reflections, shadows, ambient occlusion or global lighting. In Portal with RTX, ray tracing takes over almost everything previously rendered with rasterization. All primary rendering is ray tracing, which only makes rendering more expensive initially. However, it offers some good cost benefits: Any glass can be refractive, as the primary rays for visibility bend as they interact with glass, giving them the rippled surface appearance you see in real life. Rays can be tracked through the title portals without sacrificing quality in the original version of the game.

A deep dive into Portal with RTX, RTX Remix – and specifically path trace rendering!

Portal with RTX also tracks all direct lighting and renders shadows and lighting in real time – something completely absent from the original. Objects that move now have shadows that move with them, particles receive the light of their surroundings, and emissive surfaces like signs emit light dynamically, whereas in the original game lighting stayed static no matter what. Portal with RTX also tracks all indirect lighting and defaults to four bounces on the Ultra setting. Because of this, reflections look way better than in the hybrid ray tracing game: the light bounces around in the reflections, giving them much better shading. This is another reason why Portal with RTX can look so different from the original in many scenes.

Along with this new lighting comes new benefits to the textures and geometries that fill the game world – and the difference, upon closer inspection, is huge. Assets that were originally limited by the geometry and texture capabilities of circa 2005 GPUs now have incredibly detailed surfaces, while some textures have been replaced with full geometry. Portal wasn’t exactly a top game in terms of texture or geometric quality when it came out in 2007, but it now rivals the quality of materials and geometry that we’re seeing in titles releasing in 2022. However, this has proved bizarrely controversial if you don’t like it or any of the other changes, you can always replace the texture yourself if you wish, or if you don’t like the new elements (although I honestly have no idea why you shouldn’t), you can change them. You can turn them off in the RTX Remix game options, which you can access by pressing ALT and X.

On to performance, where current internet wisdom suggests only RTX 4000 GPUs can run them at a playable framerate, which is both right and wrong. A new Ada Lovelace card is definitely required to play the game on ultra settings with a higher resolution of 60 fps or higher. I played the game without DLSS 3-frame generation in 4K DLSS performance mode on an RTX 4090 with a Core i9 12900K capped at 60 fps. It only dropped two frames while beating the entire game. I thought it was excellent, but of course I’m relying on the DLSS 2 image reconstruction here. Native 4K is a write-off in terms of performance – simply due to the sheer amount of RT processing the game delivers.

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Portal, on its Ultra settings, does the most intense path-tracing ever put into a video game: it uses four raw bounces with no cheating with fallback structures, so your GPU will be humbled by it. However, you can also better prepare your PC to run by adjusting settings and using a lower DLSS mode than you might be used to. Choose the High preset, set the maximum number of path-tracing bounces to two, and reduce the Denoiser quality, and you’ll retain the lion’s share of the visuals while radically improving performance. In addition to these recommendations, I also recommend leaving the volumetric lighting on, as it can significantly improve the atmosphere. I also suggest leaving textures on Ultra and setting particle lighting to Ultra, which provides obvious particle lighting at a low performance cost.

For older Ampere or Turing cards, choose high settings further down the stack and set the maximum amount of flare to one (for the record, one flare is equivalent to what Quake 2 RTX does). You can also experiment with lower than expected DLSS settings – the Ultra Performance mode looks extremely good at 4K, likely due to its clean art style and because the game has little to no ultra-thin transparencies common to lower-end DLSS modes cause some problems. Obviously, resolution has the biggest impact on performance, so be sensible in your goals and don’t shy away from DLSS.

I’d say there’s a path to decent performance on almost every Nvidia RTX card – I’ve even had good results with an RTX 2060 Super – but the same isn’t true for AMD. Radeon GPUs are less impressive than Nvidia counterparts in terms of RT performance, but the experience just sucks here, and since the game won’t even launch on Intel GPUs, Nvidia needs to put in the work here to provide all users with performance to offer a decent experience hardware. The implementation of DLSS-3 frame generation also needs improvement as it never feels smooth with or without v-sync. Frame rate gain is as high as it should be, but camera movement has jitter and rubber banding issues – and that’s why I’ve stuck with DLSS 2 for my gameplay.

In summary, I think Portal with RTX is simply fantastic. The new lighting model breathes life into an old game that I would otherwise never have visited again – and it made me appreciate Portal even more since it’s no longer bound by the technical limitations of the Source engine. That’s what RTX Remix will do for a lot of titles when it’s fully released – people across the web have already put Portal RTX’s remix files into games like Max Payne, SWAT 4 and more, and even without replacing assets, RTX Remix works magical that’s hard to believe. Imagine what it can do when users have total fine control – a ray tracing revolution is upon us and I can’t wait to see the results.

Download at: https://www.eurogamer.net/digitalfoundry-2022-portal-with-rtx-and-the-new-retro-ray-tracing-revolution

Fry Electronics Team

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