GTA 6 的 HDR 实现或为廉价 SDR 升级，预告片分析发现高光无额外细节

The GTA 6 launch trailer published yesterday cemented the fact that Rockstar's massively anticipated open world game is indeed coming out in just a little over a month. But like any GTA trailer, it was also thoroughly analyzed frame by frame.

Fans usually try to spot specific cars, NPCs, or weapons. Filippo Tarpini, on the other hand, being an HDR and tonemapping expert, focused on that side of the trailer. In a lengthy X thread, he went through some of the tonemapping shortcomings that emerged from the GTA 6 launch trailer:

However... as often happens: bright blue turns purple! See the pool jump scene below. This is a typical trait of tonemapping per channel; Unreal/ACES have a "blue correction" feature to remedy this problem, which introduces more issues like banding. So, our best guess is that they are using AgX! It's per channel; it usually doesn't escape this problem. In fact, it can even make it worse, given it has no gamut adaptation. AgX produces colors that are not representable in sRGB, then clips them, causing hue shifts like blue->purple. As proof of that, we have the broken gradients around the pool lights ("banding"). If we tweak levels, we can see edges very clearly.

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Why AgX? Most studios follow trends for tonemapping, copying whatever they've heard is good nowadays. GTA 5 and RDR2 used Hable (Naughty Dog), which, along with ACES, dominated the PS4 generation. Neither is really satisfactory anymore, and with barely any alternatives out there, everybody is jumping on AgX. However, AgX has one problem... There's no official HDR implementation of it, and nobody in the industry seems to be able to adapt its math to HDR (well, I can!). Here's the original vs quickly re-tuned version to make reds more orange (less "pink"). Ignore hue changes in other colors; they wouldn't be there if I did this properly, and it'd certainly be possible to do so in the game's code.

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@MusaRenoDX has analyzed the HDR footage and believes they are using inverse tonemapping for HDR, as there's no extra detail in highlights. That does not bode well! GTA 6, the biggest game in the world using a cheap SDR-to-HDR upgrade method would be a real shame, but we have come to expect the worst when it comes to HDR.

Unfortunately, he's correct. As we discussed in our exclusive interview from last December, HDR gaming is in a sorry state, especially on PC. Tarpini is trying to remedy that, but he's just one man, after all.

As for GTA 6, we'll have to wait until the game is in our hands to evaluate the HDR implementation. Even so, there will be no way to fix it until the release of the PC version, which is rumored to be targeting a Q1 2027 launch window.

About the author: With over two decades of experience in gaming journalism, Alessio Palumbo has led the gaming vertical at Wccftech since August 2015. He started working at a young age for Italian websites like Everyeye.it, Gamestar.it, Nextgame.it, and Multiplayer.it before kickstarting the indie English-language publication Worlds Factory as its founder and Editor in Chief. In the last decade, he has coordinated the overall output of Wccftech's gaming section, managed PR relations, assigned reviews, produced daily news coverage, edited gaming content as needed, and delivered game reviews. Arguably, his trademark content is the long series of exclusive developer interviews that have been cited by Wikipedia and by the biggest news media and gaming publications. His passion for technology also makes him knowledgeable when it comes to gaming hardware and tech. His favorite genres include RPGs, MMORPGs, and action/adventure games.

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