Benchmarking non-photorealistic rendering of portraits

We present a set of images for helping NPR practitioners evaluate their image-based portrait stylisation algorithms. Using a standard set both facilitates comparisons with other methods and helps ensure that presented results are representative. We give two levels of difficulty, each consisting of 20 images selected systematically so as to provide good coverage of several possible portrait characteristics. We applied three existing portrait-specific stylisation algorithms, two general-purpose stylisation algorithms, and one general learning based stylisation algorithm to the first level of the benchmark, corresponding to the type of constrained images that have often been used in portrait-specific work. We found that the existing methods are generally effective on this new image set, demonstrating that level one of the benchmark is tractable; challenges remain at level two. Results revealed several advantages conferred by portrait-specific algorithms over general-purpose algorithms: portrait-specific algorithms can use domain-specific information to preserve key details such as eyes and to eliminate extraneous details, and they have more scope for semantically meaningful abstraction due to the underlying face model. Finally, we provide some thoughts on systematically extending the benchmark to higher levels of difficulty

3DCGアニメーション技術を利用したインドネシアの伝統的な演劇芸術の保存

There are various types of traditional theater art called Wayang in Indonesia. One of them is Wayang Beber of Pacitan, which originated in the 17th century and has a long history of over 400 years. Despite the precious value of these art works as cultural, historical, and religious heritage of Indonesia, their preservation is currently in a critical condition. Because of the humid climate of Indonesia it is hard to keep pictures in a good condition, and in addition, the country is experiencing a dramatic decrease in the number of artists to draw them, lack of budget for preservation, and lack of overall national interest in the preservation of Wayang Beber of Pacitan. It is feared that without a quick action, Wayang Beber of Pacitan could be lost in the near future. The purpose of this research is to preserve the Wayang Beber of Pacitan in a reasonable manner, so that Indonesian cultural heritage survives eternally. In order to solve the problems, the author proposes an application of 3-Dimensional Computer Graphics (3DCG) technology as a tool to reproduce and save the art digitally. The author then develops a 3DCG system specifically to generate Wayang Beber of Pacitan art works. As an example, some digital art reproduction works of Wayang Beber of Pacitan are generated using the proposed system. This thesis consists of 6 chapters: Chapter 1 describes background, scope, and objectives of the research. This chapter also provides literature survey related to digital preservation of cultural heritage, and specific nonphotorealistic CG techniques such as silhouette rendering, pattern generation. Chapter 2 discusses the research to compile archives of Wayang Beber of Pacitan. This research is performed by surveying related research works, observing the actual artwork and gathering data from interviews. The results of this survey are used as a basis for analyzing the visual style of Wayang Beber. After the identification of characteristics of the visual style, details of the required method for converting the pictures into 3DCG animation are determined. The original Wayang Beber is composed of many parts. It is difficult to create parts one by one in 3DCG, therefore a method that can generate the picture semi-automatically is considered to be used. Chapter 3 discusses the development of an outline shader. This shader is used to simulate outlines of Wayang Beber pictures on a 3DCG model. Outlines of Wayang Beber have some typical characteristics, such as expressive brushstrokes and variations in thicknesses. To produce an outline with these characteristics, a shader that incorporates object-based silhouette detection and a non-uniform point displacement algorithm is proposed. Chapter 4 discusses the development of the shader to generate ornamentation for rendering Wayang Beber characters’ textiles patterns. The characters of Wayang Beber have many characteristic patterns on their textiles. These patterns would require plenty of hard work during the 3DCG animation production of Wayang Beber. This research proposes a semi-automatic system utilizing a shader that uses procedural pattern generation based on shape grammars. Using this system, artists can easily create and modify details of the pattern including shape, size, quantity, color, and arrangement. Chapter 5 discusses key pose extraction and interpolation of in-between frames for animating CG characters made from Wayang Beber of Pacitan paintings. A Wayang Beber painting is a still image that does not have motion from it. Therefore, it appears that it would be very difficult to make a cartoon movie. However, P. Tabrani showed in his study that the essence of motion does exist in these historical paintings. In this research, a new technique was established using the theory developed in Tabrani’s study and the author have succeeded in extracting key poses from Wayang Beber of Pacitan works. Next, in-between frames are needed for the purpose of making a cartoon movie from the extracted key poses. The interpolation in this research is based on the principles of Wayang motion. The principles are derived from movements in other types of Wayang performances, such as Wayang Orang and Wayang Kulit. Using the method proposed in this research, the key frames and in-between frames for animating the characters are able to be provided adequately. Chapter 6 contains the conclusion and the summary of this research. The quality of digital eproductions of traditional drawings using this 3DCG system and the usability of this system are checked and evaluated. Using the methods proposed in this research, it is possible to create 3DCG animations from other types of Wayang Beber. The author intends to propose this 3DCG system to the Indonesian government as a tool for the preservation of traditional theater art in order that this research can contribute to the survival of cultural heritages in Indonesia.首都大学東京, 2015-09-30, 博士(芸術工学）首都大学東

Authorial subjective evaluation of non-photorealistic images

I argue in favor of a systematic subjective evaluation of non-photorealistic images. Objective measurements are hard to design, and quantitative user studies are problematic for a multiplicity of reasons. Subjective evaluations are not quantitative but are faster to conduct and offer the chance to dig into subtleties that are obscured by numerical scores. By carefully laying out the important elements of the intended image style, and then evaluating their results according to their adherence to the style, researchers can produce convincing evaluations with a manageable level of effort