Translated by Optical Flow

Since its launch in mid-May, Gakuen Idol Master (later referred to as Xuemath) has become the strongest new game among Japan's local products this year, not only regularly topping the best-selling App Store charts, but also maintaining the stability of breaking into the top 10 "every revenue peak".

In the previous article, we introduced some of the features of this product, to put it simply, it inherits the cultivation system and charging strategy of "Horse Racing Girl", and differentiates itself with "playing cards" in the core gameplay. The solid product foundation also allows players to connect with the new sub-IP of this idol master.

At the recent CEDEC developer conference in Japan, Takayuki Sugimura, designer and 3D director of the production team of Xuemas, and Tomoya Mihara, technical artist, shared their experience in making 3D characters and backgrounds for this game with the theme of "Details Determine Masterpieces".

Left: Tomiya Mihara; Right: Takayuki Sugimura

It focuses on how to use details to improve the charm of characters in the fully competitive and highly industrialized direction of 3D idol games, so as to fight a bloody way. The following is a compilation of the shared content, with some cuts and editing.

Before we talk about 3D visual concepts and rendering, let's take a brief look at the style and positioning of the game through a video.

01

Bringing Characters to Life

As you can see from the video, the key word of the 3D visual concept of Xuemais is "the feeling of water and spirit".

From this core element, it can be subdivided into "vitality/sense of life, sense of breathing; Vibrant, blooming brilliance; Brightness, sparkle; transparency, beauty; Novelty, freshness" and other labels.

By thoroughly understanding these labels, we achieve the goal of "the highest quality of mobile game 3D beautiful girls" in production.

In addition, instead of focusing on the multiplayer stage, the game focuses on solo concerts that are bland in terms of artistic expression, and by maximizing the quality of each character and increasing the sense of presence, the game realizes a luxurious and immersive concert scene and background effect.

The execution environment and rendering are shown in the slide below, where the scene uses about 1 million polygons.

The most important points for the character model are to make use of various lighting effects, improve the quality of hair and skin, carefully polish the shape of the body and clothing, enhance the richness and softness of facial expressions, and increase the charm and dynamism of the movements.

Multiple lighting performances

Improves hair quality

Vivid expressions

The mesh situation is as follows: the character uses about 60,000 polygons, especially nearly half of the resources are allocated to the head, such as hair (2.3W~2.6W) and face (8,200), and the rest is the body (2.5W~2.6W).

Although it is the norm in this day and age to model characters on consoles with hundreds of thousands of polygons, Xuemès is still careful not to waste too many resources when it comes to actual 3D model making.

In addition, each character uses more than 300 bones, which are mainly used to represent the shaking effect of the object.

There are five types of character lighting levels that control shadows, from lights to environment textures: key light, additional light, edge light, specular cubemap texture, and specular texture light texture.

By deliberately keeping the main light dark, combined with multiple additional lights, you can create a soft lighting performance. At the same time, specular reflection is the main factor that reflects the texture of the model.

Additional light

Edge light

Specular reflection

In terms of shaders, materials, and textures, the detailed specifications are shown in the slide below, and each character will use 9 shaders, 9~11 materials, and 8 textures.

The presentation and texture of the shadows are distinguished by "Def textures", as shown in the figure below, which allows HERMS to achieve the texture effect of various clothing.

Shaders at a glance

Materials at a glance

The kind of texture

Use Def to distinguish between different versions of the model

In addition, the use of shadow lamps can increase the texture of the skin. Specifically, the RGB of the texture is treated as a light for the shadow of the skin. Shadow colors are calculated instead of using shader gradient color maps. This makes it easier to bring out the original picture.

Similarly, the use of textured lamps can increase the texture of the garment. In the costume shown in the figure below, the 128x16 pixel horizontal texture is divided into 6 parts according to the ramp texture, and then overlapped together to achieve the effect.

The handling of the forehair perspective effect is also very particular. First of all, with the shader, you can show the eyes and eyebrows that can be seen through the hair; Then, through the α channel of the hair color texture, the scope and transparency of the perspective can be controlled; Then, according to different angles, the transparency effect will produce a gradient; Finally, according to different characters and different hairstyles, the angle and amplitude of the gradient are specifically adjusted.

In addition, details such as "sweat and unkempt hair" are also a key element to enhance the realism of the concert scene.

Next is the "Facial Expressions of the Character Model". The rich character facial expressions are made up of four elements: bones, BlendShapes, decals, and MotionEffects.

Bones are used to represent the animation of the pupil's gaze and the animation of the tongue. The pupil animation is basically only turning; Animating the tongue involves moving, rotating, and scaling, all of which have already been implemented.

BlendShape is processed on a per-mesh basis, so the cost of shape processing is relatively high, but this problem can be avoided by using the GraphicsBuffer's Skinning function to achieve high-speed processing and reduce consumption.

Decals are used to express blushing and pale expressions. Generally speaking, you use Unity's standard features directly, but for the problem of not being able to control the animation, we use it after modifying it. Decals are often used not only to show facial expressions, but also to backgrounds.

In addition, MotionEffect is specially designed for special expressions such as circled eyes. Specifically, you can now generate an action set on the Prefab side and replace it with a texture set in the material. This way, animators can easily achieve the desired expression without having to think too much about it.

It's worth mentioning that with BlendShape, you can also modify the shape of your face according to the perspective, making your character look more photogenic and attractive.

BlendShape is also used when adjusting the tip of the nose. For example, in the image below, the nose grid displayed when viewing the character from the front needs to be moved backwards when viewed from the side to make the character's face look more natural.

02

Modeling: Standardization (X) Personalization (√)

Next up is "the details and polishing of the character model".

One of the main premises is that the body model of the character of Xuemas is not made according to the template specifications, but according to the "unique shape of each person", and these details are determined by the data such as muscle and fat in the setting of each idol character.

As a result, not only will each character's body be modeled differently, but also individual body parts, such as breasts and calves.

The most intuitive thing is that different texture drawings will directly affect the details of the character's appearance. For example, by increasing the visibility of areas such as the abdomen and adductor muscles, you can improve the realism of the concert. However, it's not good to be too realistic, so you need to be able to grasp the scope of "anime-style fakeness".

In terms of styling, Xuemais will pay special attention to the performance of the hair, especially the "tip" of the hair, and in general, where it is fine enough, Xuemais will make it thinner and longer. Whether it's loose strands or fluffy ends, the production team carefully crafts them one by one, and in order to prevent these precious details from going unnoticed, they are all bone-added.

In the same way, there are no corners in the production of clothing. In order to make the costume look "more like a real person", the game will focus on depicting the folds, material texture, and stitching details to make the costume look more "convincing".

The production team also attached great importance to the performance of "swinging". When they first started, they added not only shakable bones to the costume, but also some bones to the skin...... As a result, it didn't shake up.

In fact, it is easier to move up and down depending on the force, so it is difficult to see the effect of shaking when the character moves. Therefore, by converting the vertical force into a horizontal force, the game finally achieves a swing pattern that is close to the ideal.

The production team also created a "wind system" that deliberately caused the characters' hair and clothes to sway in crosswinds. It can be said that in terms of "swinging", the production team is uncompromising.

The audience of the concert is also a detail. The audience's models are broadly divided into two types: "low-poly model" and "crowd system". The former is composed of about 3,000 polygons, while the latter has 500 to 1,000 polygons, which are dynamically adjusted according to the requirements of quantity and quality.

Among them, the "crowd system" uses ComputeShader for processing, which has the advantage of being able to load an audience of about 10,000 people at high speed and low load.

The last detail is "the stage performance of a real concert". In Xuemès, it is not only a bunch of stage equipment and camera crews to piece together the excitement of the performance, but also a complete team for the concert, such as stage equipment, wiring and wiring, camera crews, performance consoles and so on.

03

Good Modeling Requires "Spirituality"

In general, many of the 3D art strategies from the focus to the detailed performance are based on the existing products on the market.

First of all, the core is to concentrate resources on a single character model, and reflect the vitality and tension of the concert through the styling of hair and costumes, and the details of the swing.

In addition, in the general model components, we also try to emphasize the "personality" with body details that are more in line with the character setting, and combine with the rich facial expressions of the characters to bring out the vivid postures of different characters.

Finally, in the details of the concert, the audience's sense of presence is deepened by connecting the hard performances of the idols and the fanatical attitude of the audience, and the in-depth portrayal of the stage details is combined to form a set of performance effects with great charm and sense of substitution.

As mentioned at the beginning of the article, 3D card rendering is not a new technology today, and Japan's 3D idol games have rolled up several generations of products, and now the opportunity left for new entrants is only "differentiation from the details". Learning from Mas can break through in this environment, which is enough to see that it does have real kung fu at the production level.

From this point of view, 3D card rendering products are also popular in China, but behind the successful cases are more losers and wall runners. Among them, when it comes to the road of "personality design→ modeling→ perception", many products give people the feeling that they "lack spirituality" in the last two steps, so it is easy to be confused by everyone.

And where does "spirituality" come from? How do you avoid a cookie-cutter look? I think we have to find the answer to this question through understanding, accumulation and practice. I hope that learning from the strategy of Mars to jump out of the box and pick out the details can give you some new ideas.

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