Motion capture, usually shortened to mocap, is the process of recording how a real person moves and turning that movement into data a 3D character can use. An actor performs, cameras or sensors track their body, and software converts the recording into the motion of a digital skeleton. That skeleton then drives a game character, a creature or anything else that has been rigged to move.
Mocap is everywhere in modern games, from the way a soldier vaults a wall to the small shifts of weight when a character stands still. It is also widely misunderstood. It does not replace animators, and the raw data is never ready to drop straight into a game.
What is motion capture?
At its simplest, motion capture records the position and rotation of points on a moving body many times a second. Each point is linked to a joint, such as a hip, knee, shoulder or wrist. Put together, those joints form a skeleton that moves exactly as the performer moved.
Three terms are worth separating early:
- Motion capture usually means body movement only.
- Facial capture records the face, often with a small camera on a helmet rig pointed at the actor.
- Performance capture means recording body, face and often voice at the same time, so the whole performance stays in sync. Story-driven games use this for cinematics.
The data on its own is just motion. To appear on screen it has to be applied to a character that has a skeleton and controls, which is the job of rigging. If that part is new to you, our guide to 3D rigging explains how a skeleton and its controls are built.
In games, captured data still needs an animator's eye for timing, weight and readability. Those animation skills are the core of the Animation specialisation in CADA's Certificate in 3D for Games, taught in Maya.
Types of motion capture systems
There are three main families of motion capture technology. Each one trades accuracy against cost and convenience.
Optical motion capture
Optical systems are what most people picture: an actor in a tight suit covered in small reflective balls, surrounded by a ring of cameras. The cameras emit infrared light, the markers reflect it, and software works out where each marker is in 3D by comparing what several cameras see at once.
Optical capture is the most accurate option and the standard on large game productions. Its weak point is occlusion: when a marker is hidden from enough cameras, for example when an actor rolls on the floor or two performers grapple, the system loses track of it and the data has gaps that someone has to fix. Some systems use active markers, small LEDs that light up, instead of reflective ones.
Inertial motion capture
Inertial systems put sensors inside the suit instead of cameras around the room. Each sensor combines an accelerometer and a gyroscope, and usually a magnetometer, to measure how that part of the body is moving and turning.
The big advantages are cost and freedom. You can capture in an ordinary room, outdoors or in a small studio, and nothing is ever hidden from view. The trade-off is drift: small errors build up over time, so the character's position in space slowly wanders and feet may slide or float. Metal and magnetic interference nearby can make this worse. For indie teams and previsualisation, inertial suits are often the practical choice.
Markerless motion capture
Markerless systems use ordinary video and computer vision, often machine learning, to estimate a skeleton from footage of a person. Some work from several cameras, others from a single phone video.
Markerless capture is the cheapest and fastest way to get rough motion, and it has improved quickly. It is still less precise than a good optical setup, especially for hands, fast movement and contact with the floor. Treat it as a great tool for reference and blocking, not a replacement for a capture stage on a big project.
How does motion capture work, step by step?
Whatever the hardware, a game mocap shoot follows roughly the same path.
- Planning the shot list. Before anyone puts on a suit, the animation team lists every move the game needs: walk, run, turns, starts, stops, attacks, reactions. Good shot lists save money, because studio time is expensive and missing moves are costly to reshoot.
- Calibration. The system is calibrated so it knows where the cameras or sensors are. The actor then holds a reference pose, often a T-pose, so the software can fit a skeleton to their proportions.
- Capture. The actor performs each move, usually several takes of each. Props such as weapons may be tracked too. A director or animator watches a live preview of a simple skeleton to check the action reads well.
- Solving. Software turns the raw marker or sensor data into joint rotations on a skeleton. This step is called solving.
- Clean-up. Technicians and animators fix gaps, swapped markers, jitter, foot sliding and hands that pass through the body.
- Retargeting. The cleaned motion is transferred from the actor's skeleton to the game character's skeleton, which almost never has the same proportions.
- Animation polish and integration. Animators edit the motion so it works in the game, then it is imported into the engine and connected to gameplay.
Beginners usually think the capture is the hard part. In practice, most of the work happens in steps 5 to 7.
What game animators do with mocap data
This is the part that matters if you want a job in game animation. Mocap gives you realistic motion. It does not give you motion that plays well.
Clean-up and retargeting
Raw data is noisy. Feet slide when they should be planted, fingers jitter, and a shoulder may pop for a few frames where a marker was hidden. Clean-up is often done in dedicated mocap software such as Autodesk MotionBuilder, then refined in Maya. Retargeting matters because a two-metre ogre and a slim elf cannot share one actor's motion without adjustment: stride length, arm reach and contact with the ground all change. Unreal Engine has its own retargeting tools, so studios can share one library of motion across several characters with different skeletons.
Making it work for gameplay
A game character has to respond to a button press instantly, loop a run cycle without a visible seam, and blend smoothly from a jog into a sprint. Real human movement does none of that by default. Animators trim each clip, match the first and last poses so cycles loop, and cut slow wind-ups so the controls feel responsive.
Many games also use root motion, where the movement of the character through the level comes from the animation itself rather than from code. That only works if the root bone of the skeleton carries clean forward motion, so animators often edit the root by hand.
Exaggeration and style
Real motion can look floaty or underpowered in a game camera. Animators push poses, sharpen timing and add weight to hits so actions read from a distance. Stylised games may use mocap only as reference and keyframe everything on top. Our guide to the role of a 3D animator explains where this work fits in the job.
Mocap or keyframe animation?
Studios use both, and the choice depends on the move.
- Use mocap for realistic human motion in large amounts: locomotion sets, cinematics, crowd behaviour, subtle idles and conversations. It is fast once the stage is booked, and it captures small details that are hard to keyframe.
- Use keyframe animation for anything a human cannot perform: creatures, robots, cartoon characters, superhuman attacks and very stylised motion. Keyframing also gives you exact control over timing.
- Combine them for most game characters. A typical approach is mocap for the base movement, then keyframe layers on top to fix contacts, exaggerate key poses and add hand and face detail.
Our advice: learn keyframe animation first. If you understand timing, spacing, weight and the 12 principles of animation (squash and stretch, anticipation, timing and the rest), you can judge what is wrong with a mocap clip and fix it. If you only know how to import data, you will struggle when it does not look right, and it rarely looks right straight away.
Where motion capture is used
Video games. Mocap drives locomotion, combat, traversal and cinematics in most realistic games. Sports games rely on it heavily, because players know exactly how real athletes move.
Film and TV. Motion capture of Andy Serkis's performance drove Gollum's body in The Lord of the Rings, while animators keyframed the face using his performance as reference.
Sports science and biomechanics. Researchers and coaches capture athletes to analyse movement patterns, improve technique and study injuries.
Virtual reality. VR headsets and controllers are a form of real-time motion tracking, and full-body tracking brings a player's movement into a virtual space.
Advantages and limits of motion capture
Advantages:
- Realism and nuance. Mocap records small details of balance and weight that take a long time to keyframe.
- Speed at scale. When a game needs hundreds of movements, capturing them is often faster than animating each one by hand.
- Consistency. One performer can give a whole move set a coherent feel.
Limits:
- Cost. Optical stages, actors and clean-up time add up quickly.
- Clean-up work. Every clip needs fixing and polishing before it is game-ready.
- Physical limits. You can only capture what a person can actually perform.
- Style. Realistic motion is not always what a game needs.
How to get started with motion capture
You do not need a mocap suit to start. In fact, buying one first is a common beginner mistake. Here is the order we recommend.
- Learn 3D and animation basics first. Get comfortable posing a rigged character and making a simple walk cycle by hand. Without that, you will not be able to fix captured data.
- Practise with existing mocap clips. Free and paid libraries of captured motion are easy to find. Import a clip onto a rigged character, then fix foot sliding, loop it cleanly and push the key poses. This is exactly the work junior animators do.
- Try markerless capture. Record yourself on a phone and run it through a markerless tool. Compare the result with the real video and note what breaks: hands, feet and fast moves.
- Get the motion into a game engine. Bring a cleaned clip into Unreal Engine, put it on a character and see how it looks in a real game camera.
- Show the process in your portfolio. Studios hiring animators want to see judgement. A before and after of a raw clip next to your polished version says more than a finished clip alone.
Mocap is a tool in the animator's kit, not a shortcut past learning to animate. The animators studios value are the ones who can tell when captured motion is wrong and know how to fix it.
Start animating for games with CADA
If you are new to 3D, start with CADA's free Blender 3D Bootcamp. It is six live, one-hour online sessions over three weeks, starting in Blender and finishing in Unreal Engine, and you need no experience to join.
If you are ready to commit, the Certificate in 3D for Games is a 60-week online programme. You try 3D Art, Tech Art, Animation and Procedural before choosing your specialisation. Animation is taught in Maya, and Tech Art covers rigging. Each term you work in a team on a game project, from a walkable story environment to a playable level and a vertical slice.