“Guilty Gear” series, “back side method” implementation technology to freely process contour lines[CEDEC2024]- GAME Watch

The Guilty Gear series is a fighting game developed by Arc System Works since 1998. Mr. C. Junya Motomura, who is responsible for graphic modeling, gave a lecture titled “To draw beautiful 3D lines. Toon line control techniques for the Guilty Gear series” at the “CEDEC 2024” event.

The “Guilty Gear” series is a fighting game where unique original characters fight in a flashy way. Featuring manga-like visuals, original BGM, and a fun combo system, its unique worldview has earned it many fans in Japan and abroad.

This lecture introduced the modeling techniques that support the visuals of the “Guilty Gear” series, and this article will introduce some of them.

The lectures at CEDEC 2024 will also be streamed online. Even if you can't watch in real time, you can use the time-shifted broadcast if you register for the course. The time-shifted broadcast will be released the day after the session ends, and you can watch it until 10:00 on September 2 even after the session ends, so please take advantage of it.

□CEDEC 2024 Sessions List Page.

Arc System Works is designing the main model/artist Junya Motomura.

Ideas for implementing the backside method in the “Guilty Gear” series.

The “return method” is a technique for creating an outline. I won't go into details, but the basic principle is to overlap the front and back sides of the polygons and use the protruding parts as outlines.

In the “Guilty Gear” series, various improvements have been made to this back-facing method to improve quality and efficiency. One example is the method of achieving a consistent line thickness regardless of composition, such as camera distance or viewing angle.

In games these days, subjects are often captured from different angles, such as characters standing, close-ups, and long-distance shots. Fighting games are no exception, and you will often see a character zoomed in for special scenes, such as a special action scene or a special KO scene.

If you try to create a detailed outline using a back view of a certain thickness without considering the distance and viewing angle of the camera, the line will be too thick when viewed close up, or too thin when drawn large. So, the “Guilty Gear” series solves this problem by adjusting the back view grid extrusion according to the distance from the viewpoint, and using trigonometric functions to find the appropriate line width according to the viewing angle.

Additionally, in order to express the strong and weak lines like the unique pencil drawings of the “Guilty Gear” series, we made adjustments using vertex colors. As a user, this is the performance we usually see casually, but it is clear that detailed adjustments were made to make it look natural.

Backhaul, skip and close techniques. It is important where the line is placed or not.

When voicing a character, it is as important to have a clear outline as it is to avoid showing it in unintended areas, says Mr. Motomura. The width of the outline of the back view can be changed based on the shading (a program that determines the shading, texture, unevenness, and color of the view), so you can show or hide the outline of any part of the character, or change the outline of any part of the character. It is said that the outline of the outer part of the character can be adjusted to draw lines only on the outline. For example, by adjusting the depth of the outline (such as moving it further back), it is possible to leave only the outline of the hair and prevent other outlines from being drawn.

You can add or remove lines as you like by adjusting the depth of the outline drawing.

By turning the outline headers back, only the outer outline remains visible.

The “back mesh move” technique can also be used to avoid problems such as unnecessary lines appearing on a character's face at unexpected times, such as when making a certain expression, at a certain angle, or at a certain distance. Furthermore, the problem of the mesh of the lining of the costume penetrating the surface, resulting in a dirty view, can be prevented by releasing the vertex color to push the lining outline back.

On the other hand, as a method of drawing lines deliberately, you can organize the lines precisely by closing the back of the valley areas where the lines tend to float, and openings in cylindrical structures such as gloves, clothing sleeves and hems also provide that it is possible to draw a stable line near the area.

Many of the unique techniques and ingenuity of the “Guilty Gear” series are presented, but this article is just a few excerpts. If you are interested in watching the full version of the lecture, please use the variable time mode.

It was a lecture that explained that the natural feeling that comes with playing games is achieved through the accumulation of technology and creativity. I thought it would be good to take some time to study the depth of the graphics of your favorite games that you usually play.