Quantifying the Error of Light Transport Algorithms. (30th July 2019)

• Record Type: Journal Article
• Authors: Celarek, A.; Jakob, W.; Wimmer, M.; Lehtinen, J.
• Is Part Of: Computer graphics forum. Volume 38:Number 4(2019)
• Page Start: 111
• Page End: 121
• Publication Date: 2019-07-30
• Subjects: CCS Concepts -- Computing methodologies → Ray tracing; Computer graphics -- Periodicals; 006.605
• DOI: 10.1111/cgf.13775
• Languages: English
• ISSNs: 0167-7055

Abstract

Abstract: This paper proposes a new methodology for measuring the error of unbiased physically based rendering algorithms. The current state of the art includes mean squared error (MSE) based metrics and visual comparisons of equal‐time renderings of competing algorithms. Neither is satisfying as MSE does not describe behavior and can exhibit significant variance, and visual comparisons are inherently subjective. Our contribution is two‐fold: First, we propose to compute many short renderings instead of a single long run and use the short renderings to estimate MSE expectation and variance as well as per‐pixel standard deviation. An algorithm that achieves good results in most runs, but with occasional outliers is essentially unreliable, which we wish to quantify numerically. We use per‐pixel standard deviation to identify problematic lighting effects of rendering algorithms. The second contribution is the error spectrum ensemble (ESE), a tool for measuring the distribution of error over frequencies. The ESE serves two purposes: It reveals correlation between pixels and can be used to detect outliers, which offset the amount of error substantially.