Tweakable light and shade for cartoon animation

Abstract

Figure 1: Direct manipulation of stylized shading. Our algorithms allow the user to directly click-and-drag on shaded areas and highlights in real-time to achieve results like the above. The two leftmost images show the result of the user dragging the shaded area. The remaining images demonstrate the results of dragging operations on the highlight. Starting from the initial rounded shape in the second image, the highlight is first squared, then shrunk, split into four parts, and finally shifted to the right. AbstractLight and shade in the context of non-photorealistic imaging, such as digital cel animation, are semantic notations, rather than physical phenomena. Therefore stylized light and shade should be intentionally animated instead of simulated. This paper proposes an intuitive, direct manipulation method for animating stylized light and shade in real-time. Our method provides intuitive click-anddrag operations for translating and deforming the shaded areas, including rotation, directional scaling, splitting, and squaring of highlights, all without tedious parameter tuning. Our prototype system demonstrates the algorithms in our method, which are implemented along with a real-time cartoon shader on commodity graphics hardware. This system allows the interactive creation of stylized shading keyframes for animations, illustrating the effectiveness of the proposed techniques.

Interactive toon shading using mesh smoothing

“…Although the specular term is omitted from our Phong lighting model, most of the artists desire to add a third colour to the object which represents the highlight of the shape to symbolise the shiny surface (Anjyo and Hiramitsu, 2003;Anjyo et al, 2006). Therefore, it is necessary to render this type of lighting in non-photorealistic style for enhancing the cartoonish style.…”

“…In Anjyo et al (2006), a new method to modify stylised light and shade is proposed. It allows controlling some operations such as splitting, scaling, rotation and translation on shaded regions.…”

Interactive Non-Photorealistic Rendering

“…However, a lot of the editing job is still worked by hand [13,14,15].In order to provide the users of computer graphic applications with similar efficiency for conveying shapes, several rendering techniques for controlling the shading behaviors have been presented. Consequently, Shading-based techniques are now popular for depicting 3D object shape.…”

“…[24] Current research in Non-Photorealistic Rendering is directed towards improving interactive Toon-Shading [15,23,26,27,28] to accomplish a more cartoonish like rendering. The cartoon highlight shader in [15] lets the user modify directly through click-and-drag on the dark areas and highlighting areas in real-time on a surface to draw and animate them. Anjyo et al [15] depends on the Lambertian shading rule to extract new light vector for the modified shaded area.…”

Surface flows for image-based shading design

“…Conversely, shaded appearance may be designed through a painting interface by inferring material characteristics under known illumination conditions, using optimization as well. It has been demonstrated for both realistic [Colbert et al 2006] and stylized shading [Anjyo et al 2006;Pacanowski et al 2008]. Although they considerably reduce the amount of trial and error required to reach a satisfying result, both kinds of approaches still offer a limited control on final appearance and are restricted either to physically-realistic renderings or specific stylized appearances.…”