Rigging in Animation: Definition, Process & Challenges

8 months ago   •   8 min read

By Gwénaëlle Dupré
Photo by Andrea De Santis / Unsplash

Rigging gives 3D models the ability to move. With rigs, you can make realistic animation.

At CGWire, we help animation studios from all around the world manage their 3D animation assets so we know how important the rigging process is. But do you know exactly what goes on behind the scenes and how it works? We wrote this article to explain that, and maybe give you an idea on how you can build your own animations.

In the following sections, we cover everything related to rigging: how it fits in the animation pipeline, and what steps and roles it entails. We include common best practices and tips to make it more actionable for seasoned or aspiring animators, as well as snapshots on how to use our production tracker Kitsu to make your rigging process more efficient and collaborative. Let’s get started!

What’s Rigging

Rigging is the process of creating a digital skeleton that allows animators to control the movement and deformation of characters, creatures, and other 3D objects. This digital skeleton is a hierarchical system of interconnected joints, known as a rig. Each joint has its own position, rotation, and scale values, which determine the orientation and movement of the connected parts. It is a technical craft that requires precision, creativity, and an astute understanding of anatomy and physics.

In addition to the skeleton, a rig includes controllers or controls that make it easy for animators to manipulate a 3D model using on-screen handles, sliders, buttons, or even custom interfaces instead of moving each joint manually.

For example, imagine a character lifting an arm, bending a leg, or even making intricate facial expressions. A rig could be an arm you can then animate as needed.

The deliverables of rigging are rigged 3D objects ready to animate.

Why Rigging

Rigging is the bridge between the initial modeling phase and the subsequent animation process, bringing characters and objects to life by allowing animators to manipulate 3D movements and expressions with precision. Rigging makes characters bend, twist, and stretch consistent with real-world physics to add realism.

By manipulating a character's facial expressions, body language, and gestures, animators can display complex emotions to bring more depth and personality to the animated characters, ultimately resulting in a more engaged audience.

From a purely technical perspective, rigging saves time and effort by eliminating the need to manually set up controls for every movement, enabling artists to focus on the creative aspects of their work.

Who Does Rigging

Rigging involves the collaboration of several key roles. The rigger is the primary expert responsible for creating the rig. They have a deep understanding of anatomy, physics, and animation principles. Riggers build the skeletal structure, define joint hierarchies, set up controls, and establish the parameters and constraints that allow animators to manipulate the rig effectively.

Before rigging, the modeler creates the 3D assets, including characters, creatures, and objects. They work closely with the rigger to ensure that the models are suitable for rigging, providing the necessary topology and geometry for smooth deformations and animation control.

After rigging, animators breathe life into the rigged characters. They use the rig to pose, animate, and create performances. Animators collaborate with riggers to provide feedback on the rig's features, making requests for additional controls or adjustments as needed.

A technical director may work with riggers to develop custom tools, scripts, or plugins to enhance the rigging workflow, streamline processes, or solve technical challenges.

The Rigging Process

Before: modeling & planning

Rigging takes place after the initial 3D modeling phase: the models are ready, and the riggers can access character design information including appearance, proportions, and overall movement aesthetic.

The planning phase involves analyzing the 3D models and discussing the intended range of movements, expressions, and any specific requirements with the rigging team:

  • Functional analysis - The intended actions, poses, and expressions of the 3D object, including specific challenges or constraints that may arise during rigging, such as complex movements or deformations.
  • Rig complexity - Based on the functional analysis, the rigging team determines the level of complexity required for a given rig including the number of joints, controllers, deformers, and specialized features needed.

Different objects and body parts require different rigging techniques that need to be planned for. For example, hair for character grooming requires specialized techniques to animate like simulations using physics engines.

Joint placement

Before the rigging process can begin, joint placement determines the position and hierarchy of joints within the model to guide the natural movement and articulation of a character's structure.

Joint placement directly impacts how the character will move and deform during animation and requires a deep understanding of anatomy and kinematics to ensure that the joints are positioned in a way that mimics real-world articulation.

To achieve lifelike movement, riggers strategically place joints in areas where natural bending and rotation occur like elbows, knees, and spine. The correct hierarchical arrangement of the joints is also crucial as it determines the relationship between different parts of the character's body.

During the joint placement phase, riggers consider factors such as the character's skeletal structure, intended range of motion, and the overall aesthetics of the model.

Proxy geometry

Proxy geometry is a simplified version of the character's model used during rigging. It helps improve performance and speed during the rigging process by reducing the complexity of the model: complex models with high-resolution geometry can be computationally demanding and slow down the rigging workflow. By substituting them with simplified proxy geometries with reduced polygon count, riggers can work more smoothly and efficiently.

Proxy geometry also allows riggers to focus specifically on rigging-related tasks without being distracted by the intricate details of the final model. Since rigging involves setting up controls, joints, and deformers, having simplified geometry allows riggers to quickly manipulate and test the rig's functionality without the need for complex geometry calculations.

Rig creation

The rigger builds the rig by creating the skeletal structure and defining constraints and connections between the joints to enable realistic movements.

To make rigging more efficient, riggers use a modular approach where reusable components and templates are created. This way they can quickly rig similar characters or objects, saving time and maintaining consistency across the project with a standardized workflow and a common library of assets. A clean and logical hierarchical structure is also essential for a well-organized rig to ensure that the rig is easy to understand and manipulate.

Using constraints like Inverse Kinematics and Forward Kinematics greatly simplifies animation tasks and improves workflow. Inverse Kinematics (IK) allow animators to manipulate the end effector (e.g., a hand or foot) of a character, with the rest of the limb automatically adjusting accordingly. On the other hand, Forward Kinematics (FK) provides direct control over individual joints, allowing for more precise posing and animation. However, it's important to use constraints wisely and avoid overusing them as finding the right balance between constraints and manual control is key to achieving a flexible and efficient rig.

Skinning

Skinning involves assigning weights to the character's mesh, determining how it deforms when the rig is manipulated so that the character's skin moves realistically.

One common technique to optimize the skinning process is painting skin weights, where riggers manually assign weights to specific areas of the mesh to control how they are influenced by the underlying rig. Influence falloffs are another useful technique where riggers can define how the influence of a joint or control diminishes over distance, resulting in smoother transitions between different areas of the character's mesh by avoiding abrupt deformations.

Riggers also leverage skinning tools and scripts to automate assigning weights, managing influences, and adjusting deformations, saving precious time while improving consistency. Efficiency is a key consideration in skinning: riggers aim to achieve accurate deformation while keeping the skinning process as fast as possible by optimizing the weight assignments, minimizing the number of joints influencing each vertex, and employing techniques to reduce computational overhead.

Control setup

Controls allow animators to manipulate rigs effectively. They can take various forms like on-screen widgets, handles, or custom UI elements.

Primary controls provide animators with the main features needed to pose the character's body and limbs. These controls are strategically placed and organized in a logical manner, allowing for intuitive manipulation of the rig. Descriptive names and clear labeling of the controls contribute to the rig's accessibility and efficiency, enabling animators to quickly identify and use the desired controls.

Secondary controls are also created to fine-tune specific areas of the character for complex deformations, facial expressions, or intricate finger movements to enhance the level of control animators have over the character's performance for more complex animations.

Creating user-friendly control systems is essential to ensure a smooth and efficient animation workflow, so riggers aim to design intuitive and easy-to-understand controls, even for animators who are not directly involved in the rigging process to help them focus on the creative aspects of animation rather than struggling with complex rigging setups.

Final delivery

Once the rigging process reaches its final stage and is deemed complete, the rigged 3D model is delivered to the animators for the production phase. This includes providing the animators with the necessary files and assets: skeletal structures, controls, deformers, and any additional components specific to the rig. Along with the character model, the animation team may receive accompanying tools and scripts developed to automate certain animation tasks or provide additional features tailored to the specific rig.

It’s essential for the rigging team to collaborate closely with the animators, addressing any questions or concerns that may arise during the handover: clear documentation and instructions regarding the rigs are typically provided to assist the animators.

The final delivery of the rig marks a significant milestone in the production pipeline, as it signifies the readiness of the character for animation. It is worth noting that the rigging team continues to provide support and updates to the rig throughout the production phase as required, including bug fixes and new features to fulfill new requirements.

Iterative loop

Throughout the rigging process, communication and collaboration between riggers, modelers, animators, and other stakeholders play a crucial role in achieving a well-functioning rig that meets the creative and technical requirements of the project: having the right methodologies and tools to support this collaborative aspect is important to increase productivity.

Because of this, Kitsu is an invaluable tool for rigging. Sharing 3D models with colleagues or clients becomes a seamless process: just upload your work and gather constructive feedback from the user interface:

By providing a centralized platform, Kitsu enables open communication and coordination among team members involved in the animation pipeline. Designers can seamlessly connect with modelers, riggers, and animators to ensure a smooth transition from the design phase to the production stages with delivery tracking.

Lastly, Kitsu offers version control, providing a comprehensive history of the rigging process. Designers can easily revisit previous iterations, track changes, and maintain a clear record of the design evolution. By having all the design assets in one place, designers can efficiently manage their projects, making it easier to access and update rigging models as needed.

Conclusion

Rigging breathes life into characters and objects, enabling animators to create captivating and realistic movements. It’s a highly technical job that requires a fine understanding of physics, anatomy, and 3D modeling tools, but also creative qualities to achieve the artistic vision of a production. The rigging process can be broken down into 7 main steps, but it’s also a highly-collaborative work requiring several iterations to get right. Without it, animations can seem sloppy, and unappealing, and make the animators’ job harder and costlier for the animation studio.

CGWire's Kitsu platform provides the perfect solution for managing rigging assets throughout the animation pipeline. With Kitsu, teams can seamlessly collaborate, track rig versions, and efficiently manage rigging deliverables. Its intuitive interface and powerful features streamline the rigging process, enabling artists to focus on their creative vision and deliver high-quality animations.

Subscribe to Kitsu today, it’s free to try and easy to use with your favorite digital content creation tool, whether it’s Blender, Unreal Engine, or Harmony.

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