Study on Visual Appearance Measurement and Realistic Rendering for Non-metallic Materials

• Main Authors: Yu-Cheng Hsieh, 謝侑城
• Other Authors: Tzunghan Lin
• Format: Others
• Language: zh-TW
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/t64px7

碩士 === 國立臺灣科技大學 === 色彩與照明科技研究所 === 107 === How to accurately describe the visual experience of materials has always been an issue that researchers are trying to persue. In order to solve this problem, CIE (Commission Internationale de’Eclairage) gave a clear definition for visual appearance in 2008. Visual appearance consists of the properties of color, texture, gloss, and transparency that are evaluated by quantitative analysis. According to these analysis, the rendering process of PBR (Physically Based Rendering) is introduced in this research. Those basic quantity maps, called base color, normal, roughness and metallic maps, are used in Metallic/Roughness mainstream workflows of PBR. In this research, the data with different volumetric SVBRDF (Spatially Varying Bidirectional Reflectance Distribution Function) was captured by a self-developed SVBRDF measurement system. The purpose of Experiment 1 is verifying the reality of PBR texture of our device by psychophysical experiments. There are up to 20 samples, including textiles and wall-papers, that are verified. The result of Experiment 1 is considered as the base of Experiment 2. In Experiment 2, we chose the four qualified samples to evaluate and attend to decrease the number of LED light bulbs in our system, which is important cues for roughness map estimation in SVBRDF measurement. Totally, six types of arrangement, including these cases of 33, 30, 18, 15, 9, and 3 LED light bulbs, are evaluated. The roughness maps under different number of lights were tested based on Experiment 1 by psychophysical experiment, as well. The results of Experiment 2 show that in case of 3 LED light bulbs is acceptable for the material with higher roughness. And, in case of 9 LED light bulbs is not enough for the material of lower roughness. By contrast, in case of 15 LED light bulb is just acceptable in this situation.