Square Enix's Final Fantasy VII Rebirth is about to get a Shader Injector mod, courtesy of modder David Matos. This mod aims to inject modified shaders directly into the game's rendering API, thus enabling visual improvements.
A few days ago, Matos published a showcase that demonstrates an upgraded version of UE4's Deferred Directional Light Pixel Shader. The shader's BRDFs were upgraded, and the modder also added screen space ray traced shadows and micro shadows to improve the overall graphics quality of Final Fantasy VII Rebirth. Objects previously excluded from shadow maps can be filled with the aforementioned SSRT shadows, making environments feel more grounded and realistic.
Matos also shared an in-depth technical explanation of his work. According to him, Rebirth's gameplay lighting looks noticeably flatter than its predecessor, Final Fantasy VII Remake, even though both run on the same modified Unreal Engine 4. Cutscenes still look great, but small objects, foliage, and fine surface detail often fail to cast any shadow at all during regular gameplay.
The likely reason is Rebirth's much larger open world. To support it, the developers swapped Remake's high-detail pre-baked lighting for a lighter, lower-resolution system better suited to a bigger map. That's a reasonable trade-off for performance, but it costs the game some shadow detail along the way.
Matos also explained why some obvious fixes don't work here: full ray tracing is too demanding for an open world this size, simply increasing shadow map resolution doesn't scale well over long distances, and adding more shadow "cascades" (layers of shadow maps at different distances) tanks performance by forcing the game to redraw the whole scene multiple times per frame.
His solution leans on screen space ray traced (SSRT) shadows, a well-established technique that's actually built into Unreal Engine 4 by default, but which Rebirth simply doesn't use. Instead of redrawing the scene for every light source, SSRT shadows estimate shadows using only the depth information already on screen, similar in spirit to screen-space ambient occlusion. It's a method that excels at small, close-range shadow detail, such as hair, foliage, and the contact points between objects.
Since Rebirth's actual shader is compiled and can't be edited directly, Matos had to reverse-engineer it using RenderDoc, a free graphics debugging tool, before building his improved version on top of it. Getting there wasn't free, though. An early version of the new shadows cost an extra 3 milliseconds per frame, an unacceptable hit for a 60fps target.
Through several rounds of optimization (including switching to a more GPU-friendly noise pattern and trimming the number of samples per shadow ray), Matos brought the cost down to roughly 0.44ms at native 4K on an RTX 3080, only doubling the cost of the original lighting shader for a substantial visual upgrade.
The improvement is easy to spot once you know what to look for: strands of hair casting shadows on character faces, grass and foliage shadowing the ground beneath them, and noticeably sharper shadows wherever objects meet other surfaces. The technique also isn't limited to sunlight; it works on local lights like lamps and torches, several of which currently have shadow casting disabled entirely in Final Fantasy VII Rebirth.
Unfortunately, there's no ETA on when the Shader Injector mod (which can potentially modify other shaders, too, including post-processing and other light passes) will be released to the public, but we'll make sure to let you know.
In other Final Fantasy VII Remake/Rebirth mod news, the DX12 Async Compile mod can significantly improve stuttering issues in both games.
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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