Granblue Fantasy Relink: scRGB swapchain upgrade breaks SDR overlays even when Display Mode is set to SDR

[Avalonere]

Hi,

I'm using the Granblue Fantasy Relink Luma mod on an SDR display.

When Luma is enabled, all injected overlays have incorrect brightness/gamma.
For example, the ReShade overlay's blue UI elements become extremely bright/neon-like.
Other overlays are affected as well.

My Luma settings are:

• Display Mode: SDR
• Post Process Space Type: 0
• Gamut Mapping Type: 3
• UI Draw Type: 2

A/B test:

• Luma enabled -> overlays have incorrect brightness/colors
• Luma addon disabled -> all overlays immediately return to normal

The game's original swapchain is created as:
DXGI_FORMAT_R8G8B8A8_UNORM

I noticed that the Granblue Fantasy Relink implementation currently forces:

swapchain_format_upgrade_type = TextureFormatUpgradesType::AllowedEnabled;
swapchain_upgrade_type = SwapchainUpgradeType::scRGB;

Unlike the Generic Mod, there does not appear to be a user-facing "Disable Swapchain Upgrade" option for this game.

Would it be possible to:

1. Add a toggle to disable the swapchain/scRGB upgrade, especially for SDR displays, or
2. Keep the native SDR swapchain when Display Mode is set to SDR?

Ideally this would preserve DLSS/Luma functionality while avoiding the color-space mismatch for ReShade/Steam/RTSS and other overlays.

I can provide screenshots and a ReShade log if useful.

ReShade.log

[Hiyajomaho-num9]

I personally feel that including comparison screenshots would be better.
Also, judging by the description, it seems that Luma first generates HDR and then clamps it to SDR, which is why some parts of the SDR clamping aren't done properly.
But I'm color‑blind, so I'm sorry—I don't know how to fix it. :(

[Avalonere]

Sure. For reference, this is what the ReShade overlay looks like when rendered correctly:

With the Granblue Luma addon enabled, the blue UI elements become significantly over-bright and neon-like. The issue is also visible in the game image itself: bright areas such as white clouds become heavily blown out and are uncomfortable to look at. Disabling the addon immediately restores both the overlay and the game image to their expected appearance.

I have also opened draft RFC PR #158 with a diagnostic native-SDR workaround:

[RFC] Granblue native SDR workaround for severe output color corruption

The patch preserves the game's native DXGI_FORMAT_R8G8B8A8_UNORM swapchain and disables the display-composition path. On my SDR system, this fixes both the game-image corruption and the incorrect overlay brightness/colors.

However, the PR is intentionally not proposed as a complete fix: it disables the HDR output path unconditionally and has not been tested on an HDR display. Its purpose is to demonstrate that the corruption is associated with the upgraded scRGB swapchain and/or final display-composition path, rather than being limited to ReShade itself.

[Izueh]

hmm a toggle to disable HDR completely on boot? I will consider it.