DELiGHTWORKS Developers Blog

ディライトワークス株式会社で扱っている技術や、研究開発の模様をお伝えするブログです。

SA2020. ~Anime Games: Arts and Technologies of Japanese Cel-Shading Games~

This is the details of the session where members of DELiGHTWORKS will talk at Birds Of A Feather of SIGGRAPH Asia 2020. (Japanese version is here.)

f:id:dw_okuya:20201202131650p:plain https://sa2020.siggraph.org/en/attend/birds-of-a-feather/session/120

We discuss cel-shading for video games: introduction of the current state of real-time cel-shading technologies in Japan, art attractions of cel-shading contents, future by R&D, and Q&A.

  • Date: Thursday, December 10th
  • Time: 1:00pm - 2:30pm(SGT/GMT+8)
  • Venue: Room 2
  • Organisers:
    奥屋 武志(Takeshi Okuya) 1 / 鈴木 克史(Katsushi Suzuki) 1 / 直良 有祐(Yusuke Naora) 12 / 畑 美純(Misumi Hata) 1
    1.DELiGHTWORKS Inc., Japan / 2.IZM designworks Inc., Japan

Introduction

All organisers of this BOF session work DELiGHTWORKS Inc. in Japan. First, we introduce the activities of our company so far. Next, we talk about why we wanted to hold a cel-shading section at SIGGRAPH ASIA 2020 international conference.

The Attractive Points of Cel-Shading

We will talk about the attractive point of cel-shading in 3D games from the artist's point of view. By incorporating manga expressions from the character design stage, we will explore the possibilities of new cel-shading games that are different from the reproduction of 2D hand-drawn anime. In addition, we will sort out the advantages and disadvantages of cel-shading games by comparing it with photorealistic rendering games. Furthermore, we will consider the future prospects for cel-shading expression unique to 3DCG that goes beyond the reproduction of 2D hand-drawn anime.

Differences Between World and Japanese Cel-Shading

In this section, we will share the results of investigating the differences in the current state of cel-shading between the world and Japan. In Japan, the improvement of the cel-shading method is still very active. On the other hand, the studies related to cel-shading 3DCG in English publications seems to be decreasing. Also, the methods presented in Japan are not referenced in studies around the world very much. We will briefly introduce what kind of methods have been published while looking back on the research results of the world and Japan, and also consider the causes of the gap between the world and Japan.

The Future of Cel-Shading

We will introduce the research results of our R&D section and consider the future of cel-shading from them.

Perspective Transformation and Line Rendering

In the first section on the future of cel-shading, we will talk about real-time rendering techniques for perspective transformations and lines. In the perspective transformation, the features of perspective generated in the process of 2D composition of anime are reproduced in 3DCG by changing the projection matrix. In line rendering, our method is possible to adjust both the drawing part and the thickness of the lines, which was difficult in the past. We take an approach of considering and reproducing the features of hand-drawn anime for new algorithm development. We explain the elements that are specifically focused on.

f:id:dw_okuya:20201201022844p:plain
Tilt correction by perspective transformation1, cited from [1].

Neural Style Transfer

In the second section on the future of cel-shading, we will talk about a combination of machine learning and real-time rendering techniques. Style transfer makes it possible to create touches hard to do with traditional shaders. You can bring a variety of illustration styles into your game, not just the traditional cel-shaded style, and the production flow can change dramatically. We realize that people and backgrounds are rendered differently in many animations, thus we apply for style transfer only to people to speed up the process. Demo and talk about our research for real-time rendering of style transfer.

f:id:dw_okuya:20201201022300p:plain
Overall processing flow of the real-time style transfer method 1, cited from [2].

References
[1] Takeshi Okuya, “Real-time Tilt Correction of 3D Scenes for Movement of High-angle Shots”, NICOGRAPH 2020, P-5, 2020, (in Japanese).
[2] Katsushi Suzuki, Takeshi Okuya and Misumi Hata, “Performance Optimization of Neural Style Transfer for Animated Characters in Real-Time Rendering”, The 17th ACM SIGGRAPH European Conference on Visual Media Production, 2020.


  1. The 3D models are used under the terms of the Unity-Chan license. © UTJ/UCL https://unity-chan.com/contents/license_jp/

©DELiGHTWORKS