用于2D动画的基于图像的着色管道外文翻译资料

Nanjing University of Technology

毕业设计英文资料翻译

Translation of the English Documents for Graduation Design

Original full text link :https://ieeexplore.ieee.org/abstract/document/1599118

An image-based shading pipeline for 2D animation

Hedlena Bezerra

Abstract

Shading for cel animation based on images is a recent research topic in computer-assisted animation. This paper proposes an image-based shading pipeline to give a 3D appearance to a 2D character by inspecting the hand-drawn image directly. The proposed method estimates normal vectors on the characterrsquo;s outline and interpolates them over the remaining image. The method does not limit the animatorrsquo;s creative process and requires minimal user intervention. The resulting shading pipeline can be easily applied to photorealistic and non-photorealistic 2D cel animation. In the proposed method, the animator can easily simulate environment reflflections on the surface of 2D reflflecting objects. As far as the authors are concerned, the proposed technique is the only one in the literature that is genuinely an image-based method for 2D animation.

Keywords

Cel animation；non-photorealistic rendering,；image-based shading； computer-assisted animation.

1.Introduction

Traditional animation [1], sometimes called cel animation, hand-drawn animation, cartoon animation, or 2D animation, is the most popular form of animation. The process of producing a 2D animation sequence can be roughly divided into two major stages: the drawing process and the ink and paint process. The drawing process can also be roughly broken into two sub-stages: (i) experienced animators draw the extreme poses of the character, which represent the main course of action; (ii) less experienced animators draw the inbetween drawings between the extreme poses. The main steps in the ink and paint process are: (i) drawings are traced onto acetate cels in ink; (ii) gouache or a similar type of paint is applied to the reverse side of the cels, producing paint regions, in which rims and tones are added to give the illusion of volume and illumination. A fifirst major problem in 2D animation is to keep the frame

to-frame coherence of the drawing volumes (e.g. the 4 legs of a tiger) and the painted strokes (e.g. the stripes of a tiger) as would be in a 3D character. Another main problem is to illuminate the 2D character as it were a 3D object living in a 3D illuminated environment (called the shading problem). The origin of these problems is the fact that theanimatorrsquo;s drawings and paints are really two-dimensional projections of 3D characters as visualized in the animatorrsquo;s mind. These problems become even bigger when computerassisted animation systems [2, 3] are used. Ed Catmull [4], in 1978, was among the fifirst ones to discuss the frame-toframe coherence in computer-assisted animation. The shading problem in computer-assisted 2D animation is a much recent concern [5, 6, 7, 8, 9], although some related works could be traced back to the beginning of the 90rsquo;s [10]. S. Johnston [8] discusses the shading problem very clearly, indicating that the components involved in the illumination of a point on a surface (position and surface normal) are incomplete in hand-drawn artwork - the surface normal is unknown and the position information lacks depth.

Computer assistance for traditional animation can be considered part of the new area of Non-photorealistic Rendering - we recommend a visit to the Web page by Craig Reynolds [11]. Current research on computer assistance for traditional animation focuses on two main lines: geometrybased methods and image-based methods. In the fifirst, geometric objects are created in order to support the animation process. The latter uses image-based techniques to render the 2D character without jumping to 3D geometry.

The great advantage of the geometry-based methods is the possibility of supporting both the frame-to-frame coherence and the shading process. However, these methods cannot cope with more flfluid animations, where few strokes would change the implied geometry drastically. On the other hand, image-based methods work directly with the vivid drawings made by the artist.

This paper proposes an image-based shading pipeline to give a 3D appearance to a 2D character by inspecting the hand-drawn image directly. The goal is to minimize the user intervention by extracting information based only on the 2D image. We show that the characterrsquo;s outline is the only information needed to infer a 3D aspect through an illumination model. The proposed method estimates normal vectors on the characterrsquo;s outline and interpolates them over the remaining image. As far as the authors are concerned, the proposed technique is the only one in the literature that is genuinely an image-based method. The proposed technique permits animators easily obtain the illusion of lighting in 2D animation that: does not require 3D input; avoids scene transformation to vectorial space; and automatically enhances depth and position perception.

This paper

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Nanjing University of Technology

毕业设计英文资料翻译

Translation of the English Documents for Graduation Design

学生姓名：张琬悦 学 号 ： 1716170117

Name ： Zhang wanyue Number ： 1716170117

所在学院： 艺术设计学院

College ： College of Art amp; Design

专 业： 数字媒体艺术

Profession ： Digital Media Art

指导教师： 罗榕榕 ____

Tutor ： Luo Rongrong

2020年 12 月 16 日

Original full text link :

https://ieeexplore.ieee.org/abstract/document/1599118

An image-based shading pipeline for 2D animation

Hedlena Bezerra

Abstract

Shading for cel animation based on images is a recent research topic in computer-assisted animation. This paper proposes an image-based shading pipeline to give a 3D appearance to a 2D character by inspecting the hand-drawn image directly. The proposed method estimates normal vectors on the characterrsquo;s outline and interpolates them over the remaining image. The method does not limit the animatorrsquo;s creative process and requires minimal user intervention. The resulting shading pipeline can be easily applied to photorealistic and non-photorealistic 2D cel animation. In the proposed method, the animator can easily simulate environment reflflections on the surface of 2D reflflecting objects. As far as the authors are concerned, the proposed technique is the only one in the literature that is genuinely an image-based method for 2D animation.

Keywords

Cel animation；non-photorealistic rendering,；image-based shading； computer-assisted animation.

1.Introduction

Traditional animation [1], sometimes called cel animation, hand-drawn animation, cartoon animation, or 2D animation, is the most popular form of animation. The process of producing a 2D animation sequence can be roughly divided into two major stages: the drawing process and the ink and paint process. The drawing process can also be roughly broken into two sub-stages: (i) experienced animators draw the extreme poses of the character, which represent the main course of action; (ii) less experienced animators draw the inbetween drawings between the extreme poses. The main steps in the ink and paint process are: (i) drawings are traced onto acetate cels in ink; (ii) gouache or a similar type of paint is applied to the reverse side of the cels, producing paint regions, in which rims and tones are added to give the illusion of volume and illumination. A fifirst major problem in 2D animation is to keep the frame

to-frame coherence of the drawing volumes (e.g. the 4 legs of a tiger) and the painted strokes (e.g. the stripes of a tiger) as would be in a 3D character. Another main problem is to illuminate the 2D character as it were a 3D object living in a 3D illuminated environment (called the shading problem). The origin of these problems is the fact that theanimatorrsquo;s drawings and paints are really two-dimensional projections of 3D characters as visualized in the animatorrsquo;s mind. These problems become even bigger when computerassisted animation systems [2, 3] are used. Ed Catmull [4], in 1978, was among the fifirst ones to discuss the frame-toframe coherence in computer-assisted animation. The shading problem in computer-assisted 2D animation is a much recent concern [5, 6, 7, 8, 9], although some related works could be traced back to the beginning of the 90rsquo;s [10]. S. Johnston [8] discusses the shading problem very clearly, indicating that the components involved in the illumination of a point on a surface (position and surface normal) are incomplete in hand-drawn artwork - the surface normal is unknown and the position information lacks depth.

Computer assistance for traditional animation can be considered part of the new area of Non-photorealistic Rendering - we recommend a visit to the Web page by Craig Reynolds [11]. Current research on computer assistance for traditional animation focuses on two main lines: geometrybased methods and image-based methods. In the fifirst, geometric objects are created in order to support the animation process. The latter uses image-based techniques to render the 2D character without jumping to 3D geometry.

The great advantage of the geometry-based methods is the possibility of supporting both the frame-to-frame coherence and the shading process. However, these methods cannot cope with more flfluid animations, where few strokes would change the implied geometry drastically. On the other hand, image-based methods work directly with the vivid drawings made by the artist.

This paper proposes an image-based shading pipeline to give a 3D appearance to a 2D character by inspecting the hand-drawn image directly. The goal is to minimize the user intervention by extracting information based only on the 2D image. We show that the characterrsquo;s outline is the only information needed to infer a 3D aspect through an illumination model. The proposed method estimates normal vectors on the characterrsquo;s outline and interpolates them over the remaining image. As far as the authors are concerned, the proposed technique is the only one in the literature that is genuinely an image-based method. The proposed technique permits animators easily obtain the illusion of lighting in 2D animation that: does not require 3D input; avoids scene transformation to vectorial space; an

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