Inter-color NPR Lines: A Comparison of Rendering Techniques

• Published in: The computer games journal. Vol. 5; no. 1-2; pp. 39 - 53
• Main Authors: Herring, Donald G., McGraw, Tim
• Format: Journal Article
• Language: English
• Published: New York Springer New York 01.09.2016; Springer Nature B.V
• Subjects: Algorithms; Color; Computer Science; Rendering; Statistical analysis; Nonphotorealistic rendering; Inter-color lines; Cel shading
• ISSN: 2052-773X; 2052-773X
• DOI: 10.1007/s40869-016-0022-3

Renderings of 3D scenes can feature lines drawn automatically along sharp edges between colored areas on object textures, in order to imitate certain styles of hand-drawn line art. However, such “inter-color lines” have been studied very little. Two algorithms for rendering these lines were compared in this study—a faster one utilizing precomputed lines “baked” into the textures and a more complex one that dynamically generates the lines in image space on each frame—for the purpose of determining which of the two better imitated traditional, hand-drawn art styles and which was more visually appealing. In this study, test subjects compared results of the two algorithms side by side, both passively and interactively from a moving camera, and they noted the visual differences to reach final judgments as to which better adhered to artistic conventions and which was more appealing. Statistical analysis of the sample proportions that preferred each algorithm did not show that any significant difference existed between the two algorithms in terms of either of the above metrics. Thus the algorithm using precomputed lines appears to be more recommendable overall, as it is known to be computationally faster, whereas the dynamic algorithm was not shown to be preferred by viewers in terms of conventionality or aesthetics.