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Movement Analysis

Keyframe animation or motion capture: When to choose different approaches

03 Aug 2022

Animation is a series of images brought together to make an object or living creature – be it a person or animal – appear to be in motion. Described by ​​visual computing and computer graphics professor, Michael Gleicher, as “a uniquely expressive art form”, he explains that animation “provides the creator with control over both the appearance and the movement of characters and objects. This gives artists tremendous freedom, which when well used, can create works with tremendous impact.” The ability to create this visual impact has changed dramatically over the years. So much so that there are many different ways to create the illusion of motion. Which brings us to the subject of this blog – different animation methods and which you should use. 

While many forms of animation have been created over the years, this post will unpack two approaches – keyframing and motion capture – exploring the benefits of each and outlining how/when to use them. 

What is keyframe animation?

Keyframe animation – keyframing – is a fundamental element of creating animations, effects and motion graphics. When creating an action in a digital animation sequence, you need to define the start and end points for this action: a ball rolling from point A to point B, for example. The starting and endpoint are key markers for the motion you’re trying to create and are called keyframes. Unlike frame-by-frame animation, keyframing only selects certain frames – the key frames – and then the bits in between are calculated for you by computer. This detail that happens in between, the intermediate positions of the ball you are animating, is created via a process called “in-betweening” or simply “tweening”. This determines how many frames are needed to create movement. When all of these frames are played in succession, the result is a simple keyframed animation.

What is motion capture?

Motion capture is the process of tracking and recording the movement of an individual or object to recreate their movements. Also known as performance-capture or mocap, this approach to animation utilizes motion-tracking cameras, specially designed and placed markers and a computer equipped with animation software. Mocap traditionally sees an actor dressed in a mocap suit or being fitted with visual markers on key locations of movement on the body, such as the joints. The camera tracks these markers and sends the movement data to a computer, where it is used to position 3D characters or objects.The development and evolution of motion capture for animation has brought about some of cinema’s most groundbreaking characters, perhaps one of the most memorable being Gollum from Lord of the Rings.  

Both approaches have their place and it’s rarely a case of one or the other. In fact, it is quite common to use both. For example, if you’re creating a comical chase scene and you want the character’s head to rotate a full 360-degrees, you’ll likely use some mocap and some keyframing. 

Key reasons to use mocap

Where keyframing can be quite tedious and time consuming, mocap reduces the overall production cost by speeding up the process, it also reduces post-production time. Mocap software enables a significantly larger amount of animation data to be produced compared to traditional animation techniques. This data can be edited and reused for other, slightly different movements. 

Below, we highlight a few key reasons why mocap is a particularly appealing option. 

  1. Realism: Because mocap is able to capture real motion, it is possible to create a character that really does look like someone walking or running properly and convincingly. Only VERY skilled keyframe animation can produce this level of realism but it’s a skill that takes a lot of time and effort to develop. 
  2. Production efficiency: Let’s imagine you want to create an army of robots. With mocap you have all the data you need to make slight variations to each one – so they don’t all look exactly the same – without spending too much time on it. In this way, mocap makes financial sense because it’s easier to churn out a lot of characters, rather than getting an army of keyframing animators to tackle this task of creating the same army.
  3. Signature moves: If you’re looking to recreate Tiger Woods’ golf swing, his ‘signature move’, a keyframe animator will struggle to recreate it. Even asking a mocap studio to do this would be tough. If you’re trying to animate something that only one person can do, you really have to capture the actual thing to make it look and feel authentic.
  4. Bespoke moves: Almost a subsection of the signature moves point above, if a director has a clear picture in his mind of what he or she wants, it’s far easier for this director to realize their vision when a mocap actor is standing in front of them. Keyframing takes a week to produce and then if the director doesn’t like something specific about what has been created, the animator will need to go back and do it over again. Making changes in mocap is far easier because you can tailor the movement or instruct the actor to make a change in real time. 

This is why mocap is so popular across a wide range of fields beyond TV and film. Our software has been used to study the body movements of police force members wearing body armor and tactical vests in an effort to prevent injuries. It’s even been fitted to a drone in a wind tunnel and used to explore how this unmanned aerial vehicle could be used to detect gas leaks.

Want to find out more about our mocap solutions? Request a demo today.


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