A model of the Unity High Definition Render Pipeline, with applications to flat-panel and head-mounted display characterization

TL;DR

This paper presents a mathematical model of Unity's HDRP, highlighting its nonlinearities and providing methods for gamma correction to ensure accurate luminance and color stimuli in experiments.

Contribution

It introduces a detailed model of HDRP's luminance and color rendering, including software tools for gamma correction, improving stimulus control in experimental settings.

Findings

HDRP exhibits nonlinearities in material and rendered values.

Proper configuration can achieve gamma-corrected luminance and color.

Software tools facilitate creation of gamma-corrected stimuli files.

Abstract

Game engines such as Unity and Unreal Engine have become popular tools for creating perceptual and behavioral experiments in complex, interactive environments. They are often used with flat-panel displays, and also with head-mounted displays. Here I describe and test a mathematical model of luminance and color in Unity's High Definition Render Pipeline (HDRP). I show that the HDRP has several non-obvious features, such as nonlinearities applied to material properties and rendered values, that must be taken into account in order to show well-controlled stimuli. I also show how the HDRP can be configured to display gamma-corrected luminance and color, and I provide software to create the specialized files needed for gamma correction.