Artistic Rendering of 3D Models with Levels of Abstraction
Takashi Yoneyama, Etsuo Genda, Kunio Kondo · International journal of Asia digital art and design · 2009
In this paper, we propose a rendering framework for illustrational expressions with levels of abstraction based on our analysis of abstraction levels of drawings such as illustrations. In illustrations and other images, objects are drawn with their depictive details (levels of abstraction) being varied according to distances from viewpoints to objects and according to importance of each object. In this study, we kept this point in mind as we analyzed changes in forms and colorings of objects drawn in actual illustrations, in terms of levels of abstraction. As a result, we were able to classify abstraction levels found in objects' forms into and material. At same time, we classified changes found in colorings into the number of colors and and saturation contrast. The rendering framework we propose here is divided into two stages of off-line preprocessing and online rendering processing. As input data, we use a simplified 3D form model set which consists of abstract models of overall forms, and a surface material set whose depictive details are changed according to levels of abstraction. Further, in preprocessing stage, we produce a surface detail set in order to abstractly represent surface details included in form surfaces, such as asperities. Using these tools, we draw illustrations at rendering processing stage, based on abstraction levels of rendering points on models, which are decided dynamically according to locations of viewpoints and directions of eyes. The rendering process consists of and material texture as controlling elements for form, and coloring and tone as controlling elements for color. With illustrational representation method we propose here, we can realize interactive rendering by controlling levels of abstraction, which is a combination of two concepts of levels of details, a technique to reduce calculation costs when drawing dynamic 3DCG, and changes in depictive details when drawing illustrations. In this paper, we explain a rendering experiment using building models, which we conducted by using experiment system we implemented proposed rendering framework in. With this proposed method, we can produce animations and interactive scenes with illustrational representations using 3D models, where abstraction levels of images are changed both dynamically and successively.