Objective colorimetric validation of perceptually realistic rendering: a study of paint coating materials

Abstract : This work was conducted in the context of perceptually realistic image simulations of paint materials. These simulations aim at producing the same visual response in an observer as real objects given certain illumination and observation conditions. The colorimetric validation ensures that the colors in the simulated images differ from the real scene below a given threshold and human observers cannot discern between them. Most existing validations use the direct approach of comparing renderings with real scenes and are usually briefly described. We propose a colorimetric validation using radiometrically calibrated photographs as valid perceptual references of the real scene, which avoids taking spectral measurements of the scene. This paper details important methodological aspects, providing objective validation results for a Macbeth color chart and a sample paint coating. Our results show that we can achieve xyxy chromaticity differences under 3%, relative luminance differences under 5%, and CIEDE2000 differences under 10% for the Macbeth chart. In the case of a sample paint coating, achieved chromaticity differences are under 11% and average luminance and CIEDE2000 differences are under 1%. Validation by visual inspection is not addressed here.