This porting test project has been designed to aid in porting Godot's HDR output feature to new platforms. It has two scenes: the main scene and an SDR/HDR Stability Test that is suitable for use on all platform except for Linux.

This project builds on top of the official demo project to provide additional debug information and test images that are valuable when testing a new HDR output implementation.

This packed scene and its related scripts are intended to be a "drop-in" package for games that implement HDR output. Some reworking by the game developer would be needed to make this fit nicely alongside existing game settings.

The colour sweep shows all fully saturated sRGB colours and all fully desaturated (greyscale) values.

• Clip to max luminance
  • With HDR output, this simulates a display that hard-clips values in the BT.2020 colour space.
  • Without HDR output, this simulates a dsiplay that hard-clips values in the sRGB colour space.
• Min
  • Minimum value to be shown on the colour sweep.
• Max
  • Maximum value to be shown on the colour sweep.

Markings:

• Log scale markings (bottom of greyscale bar)
  • For example: 1.0, 2.0, 3.0, ..., 9.0, 10.0, 20.0, 30.0, ..., 90.0, 100.0, 200.0, ..., etc.
  • The tall marking indicates 0.001, 0.1, 1.0, 10.0, 100.0, etc.
• Max luminance marking (top of greyscale bar)

• Show linear 0.0, 1.0, and the maximum value based on current Max Luminance

• Middle vertical rctangle is max luminance
• Left and right sides display different stops (log base 2) relative to the max luminance

The bottom-right red, green, and blue rectangles will show negative sRGB values if they are being sent to the display:

The sdr_hdr_stability_test.tscn scene can be used to verify that output is stable between SDR and HDR. In this scene, all colours should be identical regardless of HDR or SDR output except for the "max green" rectangle:

Note: This test scene is only suitable for use on platforms that use the nonlinear (piecewise) sRGB transfer function to decode SDR content for transport over an HDR signal! This means this test scene should not be used on Linux/Wayland platforms, especially not ones that use Gamescope.