Think back to all the CG characters you can't get enough of from your favorite films, TV shows, and video games. For those characters to become virtual entities with personalities, a control system, or rig, was developed to transform them from static and lifeless models into "living and breathing" creatures that are able to convey emotions and are capable of having a thought process.
Rigging is an essential aspect of any project's pipeline. A rigger, or setup artist, provides animators with the controls needed to tell an envisioned story in the most entertaining way.
In this article, Digital-Tutor’s lead rigging and animation tutor will help you start your rigging journey. Take the first step here and find a free course on the topics covered at digitaltutors.com/start_rigging today.
So, you're ready to rig, but where should you begin? Perhaps you should start with the face, creating a complex control system that is capable of doing anything and everything. Or is it best to begin at the feet and work your way upward? Well, none of these are necessarily good starting points.
In a logical sense, the very first step in designing a control rig is to find out what the rig is expected to do. In the end, this will save you a lot of time—preventing you from adding too much control or forgetting to add features that are needed in order for the character to perform a certain way. Create a list of features your rig should have and don't be afraid to ask for clarity from your lead.
Figure 1: This is an image of the final rig built in the “Quick Start to Rigging in 3ds Max: Volume One”
Once your list is complete, you can then start to prioritize each task. Even this can be a bit of a challenge. How should we prioritize each step for the sake of efficiency? If our planning is done right, we can mitigate the time spent modifying our rigs with extra features or troubleshooting issues that may arise. The following sections will focus on a breakdown of how your tasks can and should be organized from start to finish.
Creating a Skeleton
The preliminary step in setting up a control rig is to build a skeleton, which makes it possible for characters to deform in a way that resembles realism while providing basic points of articulation so our models can be posed and animated. In Autodesk® 3ds Max®, skeletons are designed with virtual bones that are similar to the bones in our bodies. In that, they have the same purpose.
It's recommended to finish creating a character's skeleton entirely before adding controls and other features. This way, if we realize our deformations are off at this early stage, which is often the outcome when bone objects have not been placed at natural articulation points, it's much easier to make any necessary changes now rather than further along in the rig's development. This will prevent work having to be redone in order to fix the problem. You can see how creating the skeleton first can save a ton of time and effort.
Once the skeleton is complete, we can move to the next step, which involves skinning the model and polishing its deformations.
Skinning Your Model
Skinning, which is also often referred to as enveloping, is the process of binding geometry to follow the transformations of bones. When a mesh has been skinned, each of its points is controlled, or weighted, by the envelope objects we've assigned to it. This influence can be increased or reduced, producing a smooth falloff when the envelope object is moved. What's interesting and rather convenient is that 3ds Max offers more than one time-saving method to refine skin deformations.
One of the fastest ways initial refinements can be made is by directly manipulating envelopes. In 3ds Max, envelopes are represented as handles that flow along the length of a bone object. When selected, we have access to inner and outer bounds that control the envelope's influence area. By modifying these bounds, we can determine the initial weighting a bone object should have, which is truly a time-saver. However, this approach can only take us so far, and we'd soon realize that more effort would have to be put into modifying more challenging areas such as the feet, shoulders, and hands.
This is when we would want to take advantage of other skin-editing features that are used to improve the quality of our deformations, one of them being a paint brush that lets us interactively paint how much or how little influence each bone object should have over a weighted point.
Another tool we can use is the Weight Table, which gives us all weighting information on every vertex of a skinned model. We would use this to set weighting values that are very specific. We can also choose to mirror weighting information, which transfers influence data to the opposite half of a model. This saves a great amount of time by allowing us to focus our efforts on one half of the model. We can even go a step further and export all the model's influence data into a separate file, which becomes extremely useful when we need to reapply a skin modifier after making modifications to our bone objects.
Figure 2: This image shows a skeleton in action as it deforms a model
After we have finalized our skin deformations, we can then start to think about how our model will be controlled.
Utilizing Inverse Kinematics
Typically, you'll find inverse kinematics, or IK, being used to simulate the movements of arms and legs, yet there are other IK systems in 3ds Max designed for more advanced behaviors. Using inverse kinematics on our model's limbs allows animators to move them naturally so they can accomplish their task of creating believable performances.
Though IK systems such as 3ds Max's History-Independent Solver, make it possible for us to animate the arms and legs quickly, there is still more to be done to complete the setup. An IK solver, by itself, isn't enough to animate the action of a foot planting on a floor or a hand resting on a counter top. This brings us to the next step: The process of setting up control objects.
Control objects make it convenient for animators and other artists to pose and animate characters. Normally, they are built from a spline because splines do not render by default, which makes them ideal control objects.
Controls are often placed on each area of the model we want control over. Using the example in the previous section on inverse kinematics, if we wanted to set up an IK arm rig, we could create two controls: One placed at the wrist to drive its orientation while controlling the position of the arm, and other to control the elbow.
Areas on a character such as the torso and head should also have control objects in order to animate the character's body in an animator-friendly way. But there are other areas such as the fingers and eyelids that don't necessarily need objects. Instead, we can take advantage of tools such as the Parameter Editor to build custom channels that can be wired to control secondary aspects of the model. These custom parameters can also be utilized to regulate advanced features we implement to make an animator's life easier. In the next section we'll take a look at an example of this.
Designing Automated Systems
A setup artist should always look for ways to automate systems on a rig that would be very cumbersome to animate. On a character, one range of motion that can certainly be automated is a foot roll. As a matter of fact, if a foot roll were not automated, there would be a ton of counter-keying involved just to have the feet appear to roll off of a surface during a walk cycle, for instance. At best, the movement would look jittery and unappealing.
Thankfully, with the use of a few 3ds Max Helper objects, constraints, and the Reaction Manager, we can integrate a system like this quickly.
Also, remember that automation is nice and can save us and other artists some time, but there are moments when it can make working with our rigs a hassle. For example, automating a feature on our control rig may restrict an animator from being able to use that control freely. Unless this is requested by your higher-ups, it might be best to allow animators the liberty to move the control as they please so that they can create the best performance possible.
After we have developed all of these really cool features on our control system, the rig might at this point look a bit messy because of all of the nodes we added to design the rig. This is the time when we want to start hiding all objects that animators, or any other artist using our rig, should not see. This can be done easily in 3ds Max with the use of its layer manager, or via the "Hide Selected" option found underneath the Display tab.
We should also make sure our mesh is frozen by the final file so that it's easy to grab control handles without accidentally selecting objects one didn't intend to select. Setup artists can even utilize Selection Sets to make it a cinch for animators to grab all controls to key poses faster.
Figure 3: In this image, we take a look at part of the clean-up when finalizing a rig, which involves making sure all controls are operational and are easy to select
By the end of this step, our rig should basically be complete and ready for hand off to the next artist. It's easy, at this moment, to try to wrap things up so quickly that we end up overlooking an area or two on the rig that can use a bit more polish. That's why it's essential that we double-check and even triple-check our work to prevent handing off a file that is soon to get sent right back to you. This brings us to our last step…
Triple-Check Your Work
We should always take the time to check our work before we label it "final." If we neglect this very important step, we can actually cause artists to be less productive because they would be in a constant loop with whoever was responsible for not carefully making sure all features on the rig work. Surely, that isn’t something you want to be known for!
So make sure you spend the time checking every control, every custom parameter, as well as your skin deformations, just to be reassured that all is well.
Having the skill set to rig characters and creatures is truly a rewarding talent that can make you a great asset to your team. If you are new to this realm of the industry, keeping in mind the steps covered in this article can help you remove the fears you might have when developing your own rig, and instead make your experience fun and educational. And if you stick with it, you'll start to learn more creative ways systems can be designed and implemented to ultimately allow you to build the control rig you need for any project.
Keep a positive outlook and never stop learning, and you'll be well on your way to becoming a rigging specialist!
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