Character rigging is a vital aspect of bringing virtual characters to life, yet its complexity is often overlooked. In collaboration with one of our senior rigging and groom artists, Jan, we aim to demystify this craft and provide in-depth insights into the process of rigging characters for games.

In this blog, we answer common questions like:

• What is 3D character rigging?
• Why is character rigging important in animation?
• How do I get started with character rigging?
• What are the essential software and tools for character rigging?
• What are the key components of a character rig?
• What makes a good character rig?
• What are the main differences between a custom rig and an auto rig?
• What are common challenges in character rigging?
• How do I rig a 3D character for different types of animation?
• What’s the future of character rigging in the games industry?

What Is 3D Character Rigging?

Rigging is the art of granting 3D models the ability to move, bend, and deform for articulation, posing, animation, and manipulation. It demands a profound understanding of anatomy, animation principles, physics, and specific software tools. Rigging is essential for bringing 3D characters to life, making their movements and expressions believable.

A rig can be set up in many different ways and range from simple to complex, depending on the design and purpose. They can go from simple controllers, blend shapes, deformers or simple bones to full skeleton rigs with a combination of all the former.

The process of character rigging specifically, involves the creation of a suitable skeleton that enables the model to be articulated and deformed realistically, and a controller interface that allows the animator to manipulate said skeleton intuitively. It’s like building puppets but in a virtual world.

Why Is Character Rigging Important In Animation?

Character rigging plays a pivotal role in the animation pipeline, positioned right after character modelling in pre-production, as it will determine the character’s range of motion and expression, capabilities and behaviour.

Rigging streamlines the workflow by laying down the technical foundation required to bring characters to life, providing effective control mechanisms that not only facilitate realistic character movement and expressive animations but also establish a solid link for handling special effects, interactions and implementation that will allow artistic creativity during the subsequent animation phase.

The quality of the rig directly impacts the smoothness and complexity of the animations that can be achieved. A well-designed rig enhances efficiency, saving time and effort while fostering a cohesive creative process. It is an indispensable component of the animation and games industry, transforming character design into compelling animated performances, enriching the overall quality, and streamlining the creative workflow.

How Do I Get Started With Character Rigging?

Your 3D character model must have a clean and optimised topology, preferably comprised of quads, with a suitable polycount for performance. They should be set up in your favoured software to the proper scale and in a symmetrical and neutral pose.

You’ll need to determine the rigging and animation software and game engine you’ll use, to ensure compatibility and ease of implementation across all steps of the pipeline.

You should be prepared to provide a model and expression sheet of your character, as well as a detailed animation list to guide the rigging artist. The animation list should specify the level of stylization (realistic vs toon), the expected range of motion, the facial features, lip sync (if required), body mechanics, references, and any in-game simulations that need to be accounted for like cloth or hair.

Once these steps are covered, the rigging artist will proceed to analyse the model to determine the type of character (i.e. biped, quadruped, creature, insect, etc.), establish what kind of extremities are needed as well as any specific behaviours and attributes before going on to plan a roadmap to build the rig.

What Are The Essential Software And Tools For Character Rigging?

The software and tools depend on your goals and preferences, however, the industry standard and Jan’s personal favourite is Autodesk Maya. She loves it because it offers a comprehensive and versatile set of features and tools for creating lifelike and captivating characters, whilst also guaranteeing efficiency, accuracy and ease of implementation.

Maya is a 3D powerhouse that can handle every stage of the animation pipeline, from modelling all the way through to rendering, and benefits from compatibility with many other software and game engines. One of its strengths is its rigging tools, it lets you create custom rigs for any type of character. You can use joints, constraints, controllers, deformers, and more to give your character the structure and flexibility it needs.

You can also use Maya’s auto-rigging features, such as HumanIK, to generate humanoid rigs faster. It also supports facial rigging, lip sync, and blend shapes, which allow you to create expressive and dynamic characters that can convey emotions, move, and talk like real or fantasy beings.

Maya is also highly customizable and extensible, with scripting languages such as Python and MEL, and a rich ecosystem of plugins and add-ons generally used to streamline productivity.

There are of course many other 3D rigging software in the market, each with its own set of features, advantages and limitations. Some of the other most common and popular choices are 3ds Max, Cinema 4D, Unreal Engine, Unity, Mixamo, AccuRIG, and Blender.

What Are The Key Components Of A Character Rig?

The essential components of a character rig are those that allow the character to be animated in a realistic, flexible and intuitive way. These include:

• The skeleton: Like ours, it is the structure that determines how the character will bend and twist. It is made up of a hierarchy of bones (aka joints) that define the position of the articulation and deformation points of the character considering its anatomy and geometry.
• The skin: It’s the process of connecting the mesh to the skeleton created for the character in a way that deforms the geometry and allows it to move correctly. This means defining or rather painting, the amount of influence each bone will have on the mesh. In most cases, the bones will only influence certain areas. For example, the ankle joint should only influence the ankle area of the character’s mesh. If moving that joint also deformed the face or shoulder, it wouldn’t work.
  This is one of the most important parts of the rigging process and requires a lot of finesse and anatomy knowledge.
• The controls: This is the user interface that allows the animator to manipulate the character’s pose and expression. It can be designed using different shapes and colours of curves and locators and should always be clear, intuitive and easy to select. These controls should have the attributes that will be keyframed in animation, i.e. the basics like translate, rotate and scale, as well as any custom attributes that are needed like foot roll or eye blinks.
• The constraints: These are connections that drive the position, orientation and/or scale of an object using another object as the driver. This can be a joint, a control, a mesh or a null. Constraints can also set specific limits on objects and automate the animation process.
  Many different constraints can be used for several different purposes, such as point, aim, orient, parent, rivet, etc. For example, using a parent constraint to attach a weapon to the character’s hand, or control the movement of the eyes of a character using an aim constraint. Constraints can be combined and animated depending on the needs of the rig.
• The deformers: These are tools that allow further transformation or add extra shape animations to an object. The most commonly used are Blend Shapes for facial animation, however, many others can be incorporated into a rig, such as sine or jiggle.

What Makes A Good Character Rig?

A well-designed character rig enables the animator to create smooth and natural movements intuitively, whilst also ensuring that it’s stable enough to avoid any technical difficulties or unwanted limitations.

Some of the main qualities of a well-designed rig are:

• Flexibility: The rig should be able to accommodate a wide range of poses and motions, without breaking or distorting the character model. It should have enough controls to fine-tune the details of the animation, such as facial expressions, secondary motions, and overlapping actions.
• Stability: The rig should be robust and reliable, without causing any errors or glitches in the animation. It must be optimized for performance, without slowing down the software or the rendering engine.
• User-friendliness: The rig should be easy to use and understand, without requiring too much technical knowledge. It should have a clear and intuitive interface, with consistent naming and color-coding of the controls. It’s also vital that it has features that simplify the animation workflow, such as inverse kinematics, automated actions, animation pickers and pose libraries.
• Customizability: It should be adaptable and versatile, allowing the animator to modify and adjust the rig parameters, such as character scale, joint orientation, rotation order and deformation settings without the need to create a new rig for said modifications.

These are some of the key characteristics, but there may be more specific requirements depending on the type and purpose of the character. For example, a cartoon character may need a more exaggerated and expressive rig, while a realistic character may need a more accurate and detailed rig. A game character may need a more efficient and lightweight rig, while a film character may need a more complex and dynamic rig.

Is A Custom Rig Always Necessary?

A custom rig is not always necessary, as there are some cases where you can use a pre-made or a generic rig, but it depends on the type and purpose of your character and animation goals.

What Are The Main Differences Between A Custom Rig And An Auto-Rig?

A custom rig is created from scratch for a specific character. It provides more control and flexibility over the character’s movement and deformation, but it also requires more time and skill to create and use.

An auto rig is generated automatically by software or a service, such as Unreal Engine’s Mesh to MetaHuman, Mixamo, AccuRIG or Auto-Rig Pro. It can save time and budget, but it won’t be as accurate or detailed as a custom rig. It is also likely to have some limitations and compatibility issues with different platforms and formats.

To better illustrate the differences between the two, I’ll use MetaHuman as an example.

MetaHuman is a character creator framework that allows you to create realistic and high-quality 3D human characters through its web-based interface and library of presets. It also provides you with a ready-made rig for each character which includes a body rig, facial rig and control rig compatible with Unreal Engine, where it can be animated using the engine’s toolset.

Advantage

The advantage of using a MetaHuman rig is that it allows to quickly generate a character with a high level of realism and detail and is designed to work well with other MetaHuman characters. The rig also has features that simplify the animation workflow, i.e. motion capture compatibility, pose libraries, blend shapes and wrinkle maps to name a few.

The MetaHuman rig can also be used with custom meshes from scans, sculpts or traditional modelling but will always have the same topology and skeleton as the MetaHuman characters.

Disadvantage

Some of the disadvantages of using the MetaHuman rig include that it may not be suitable for all styles of characters and animation as the rig may not be able to achieve some extreme or exaggerated poses or expressions. This can result in the character not matching the aesthetic or look desired for your project. A more obvious one is that it’s designed to fit human-like characters so whilst it could be used for animal or creature bipeds, the results would be more unpredictable and/or disagreeable making the character non-compelling.

MetaHuman rigs may also have some performance issues if the polycount budget of your project is lower than the template mesh. MetaHuman characters cannot be rendered outside of Unreal Engine, meaning restricted compatibility with other software.

Therefore, the choice between a custom rig or an auto rig depends on your needs and preferences. For example, if your character has a standard human anatomy, you can use a rig that is designed for that type of character and adjust it to fit your model. You can also use online services such as Mixamo or AccuRIG that can automatically generate a rig for your character based on its shape and pose. However, a custom rig is always recommended if you want to have more control and flexibility over the rigging process and subsequent animation workflow. It’s also recommended if you want to create a unique and purpose-built rig for your character that matches its design and personality.

What Are Common Challenges In Character Rigging?

The challenges faced during the rigging process are usually varied and are directly linked to the complexity of the character. The most common can be split into 2 categories, the first one being when the model needs to go back to a previous department, and the second is related to the technical and creative skills of the rigger.

The character model needs to go back to previous pipeline steps when:

• The model isn’t optimised for rigging. This could mean, a complete retopology of the model is needed, cleaning up n-gons (faces with more than 4 sides), removing unnecessary double-sided geometry, separating mesh pieces where it makes sense or deleting interior faces that won’t be visible, etc.
• The mesh intersects with other parts of the model in a neutral pose (clipping). This can easily be fixed by repositioning the geometry or deleting the faces that are intersecting.
• The texture has an error or is stretching incorrectly when deforming, generating artefacts. This could signify an update is needed on the texture, UVs or even the model itself.
• The model resolution isn’t working, could be that it is too high-resolution causing performance issues or too low to allow for proper deformation.
• Lack of congruence in the character’s anatomy to implement the articulation points. For example, there aren’t enough loops to close the eyes, the topology of the knees and elbows results in loss of volume or isn’t placed in the right position, the eyes aren’t spherical, etc.
• Changes in the design, expected range of motion, animation list or deformations when there’s an update in the project’s scope. For example, the character can’t open its mouth, but the new animation list requires that functionality.

Technical and creative challenges:

• Creating realistic and natural deformation of the skin, especially in areas where it is likely to lose volume such as the shoulders, elbows and knees; or areas where the skin can stretch, compress, twist, or wrinkle, like the belly, fingers and face.
• Avoiding unwanted artefacts or errors in the skinning, such as skin sliding, skin popping, uneven surfaces, exploding vertex or clipping, where the skin does not follow the movement of the bones correctly or collides with other parts of the model.
• Balancing the complexity and the performance of the rig, as adding more bones, controllers, or features can increase the quality and the functionality of the rig, but also the computational cost and the difficulty of managing the rig.
• Adapting the rig to different types of animation, such as realistic, stylized, or cartoon, and ensuring that the rig can handle different poses, expressions, and motions without breaking or losing its integrity.
• Designing appealing facial expressions that match the character’s personality, making sure they don’t look stiff, generic or unrealistic.

How Do I Rig A 3D Character For Different Types Of Animation?

To rig a 3D character for different animation styles, we need to consider the following factors:

• The style and the genre of the animation (i.e. realistic, stylized, cartoon, cut out) and how they affect the design and the motion of the character. For example, a realistic character may require more bones and controllers to achieve a natural and detailed deformation, while a cartoon character may require fewer bones plus additional deformers or blend shapes to achieve simple and exaggerated poses.
• The purpose and the context of the animation, such as cinematic, gameplay, or interactive, and how they affect the functionality and the usability of the rig. For example, a cinematic character may require more features and options to create complex and expressive animations, while a gameplay character may require less features and options to optimize the performance and the compatibility of the rig.
• The rendering engine and output format of the animation, whether it’s meant for film, TV, web, gaming console or mobile will result in different quality and optimization requirements. For example, a film character may require a robust high-resolution and high-poly rig to match the visual standards and the rendering capabilities of the engine, while a web character may require a simpler low-resolution and low-poly rig to match the bandwidth and the loading speed of the platform.

What’s The Future Of Character Rigging In The Industry?

Jan believes the future of 3D Character Rigging in the industry is likely to be influenced by current and upcoming trends such as the development of artificial intelligence (AI) and machine learning technologies (ML), which can automate and enhance the rigging process.

As AI technology advances and becomes more integrated with the gaming industry, 3D character rigging may become more efficient, realistic, and versatile, opening new possibilities and opportunities for game character design and animation. However, it may also pose new challenges and risks that will need to be addressed and balanced by the riggers, developers, and users.

What do you think the future holds for character rigging for games?

Conclusion

In summary, character rigging plays a pivotal role in transforming static 3D models into dynamic, animated characters your players will love. We’ve aimed to demystify the intricacies of rigging, emphasizing its foundational significance in the animation process. From the meticulous crafting of skeletons to the development of user-friendly control interfaces, rigging artists allow animators to breathe life into characters.

A well-designed character rig not only streamlines animation workflows but also becomes a conduit for artistic expression, elevating the overall quality of animated performances. Whether opting for bespoke rigs tailored to specific characters or leveraging pre-made/auto-rigs, animators and rigging artists are tasked with striking a delicate balance between efficiency, creative control, and the unique demands of each project.

Looking ahead, Jan contemplates the potential impact of artificial intelligence and machine learning on the future of character rigging, envisioning both new efficiencies and challenges for the field.