Animation in Games - Game Developing

The overwhelming majority of games have characters that need to be animated. The exceptions to this would be games such as racing and flight simulations, or even the author’s own Starfleet Command series, which use 3D vehicle models that do not require any animation work.

So if you have kids with football helmets, monkeys inside of glass balls, space marines on a ringworld, or undead zombies, then you need animation. Animation work is as well suited to outsourcing as any other art task. In other words, it is better to have the talent in house; however, if you have too much work or just do not have the talent, then by all means look outside to solve your animation needs. The first question you must determine is whether or not you will employ artists to key-frame the animation or retain a motion capture studio and use motion actors to perform moves and capture them digitally.

The answer to this question is really easy if you are animating spiders, six-legged robots, sharks, snakes, and blobs; all of these make excellent candidates for key-framing due to the difficulty of training spiders and blobs to be motion capture performers. When I was given a tour of the House of Moves facility, I asked Jarod Phillips all sorts of annoying questions like, “Have you motion captured a snake or a waterfall?” His answer was that they tried motion capturing a dog at the insistence of a client, but it did not work out well and a skilled key-framer would have performed a far superior job and faster.

Key Framing
Outsourcing your animation work is actually straightforward. Take the finished model and textured model and hand it over to the animation house. In addition to the model and texture, you will need to supply your technical requirements such as number of bones and in what data format you want to receive your animation. You must also supply a move list that describes in as much detail as possible the moves that you want the character to perform.

Typically a key-framer should be able to perform at a rate of between one to two moves a day, varying considerably upon the complexity of the moves. Be sure to indicate in your move list what moves are intended to be looping and which are not to loop. Animation work is priced on the per-move basis with rates ranging from $25 to $150 a move or more.

Motion Capture
Motion capture is the digital science and art of recording the movement of humans with multiple cameras and using it to drive animated 3D models. In principle, one would be able to quickly obtain perfectly natural and fluid animation and drop it right on top of your model.

In practice, motion capture rivals the cost in both time and money of key framing and may cost even more. In addition, it has been common in the past for the motion-captured results to be very poor and require man-months of cleanup before being usable by the 3D model and game engine.

How Does Motion Capture Work?
The basic idea is to suit up a motion actor who has some expertise in the motions to be recorded. For example, for a SWAT game you choose to motion capture a police SWAT officer or for a basketball game you may record how an NBA star dribbles. The suit is of some black, stretchy fabric. A couple dozen little balls are glued to the suit. These balls are covered with tons of tiny reflective glass beads, the same sort of stuff you see on reflective sporting equipment such as bags for the rack on the back of a bicycle. These glass balls are designed to be efficient in reflecting light of a certain color.

Next in the setup are a bunch of cameras. The number of cameras varies depending on the facility, with a typical number being 18. These cameras do not record the movement of the actor; they record the movement of those reflective white balls.

The motion is captured in what is called the volume, the 3D box of space that the cameras are set up to view. Outside of the capture volume, the cameras are blind. To record moves such as an athlete performing a pole vault you would probably need to spend a lot of money setting up the motion capture cameras in a big open building such as a large hangar, which would also involve the costs for transporting and tuning the system. This is a good example of when you should probably break out a key-framer for the job.

Typical volumes are 16 feet by 20 feet large enough for complete walk and run cycles. Too small a volume and useful captures cannot be performed. Quite a few companies set up their own facilities and end up creating a space that is too small and have to go out of house for some of their moves! Motion capture has come a long way in quality from the early years with most advances in the proprietary software that runs the cameras in real time as the data is being collected as well as software that is run in post-production to “clean up” the motion captured data.

Cleaning up the Motion Data
After spending tens of thousands of dollars for your motion capture sessions, it would be nice if the data were to just drop in and work. The truth is the data is full of noise and errors that must be cleaned up. Each of the motion capture systems has automated tools that smooth out some of the noise in the motion and perhaps do some boundary checks. A common error is when a character makes contact with the ground, as in a tumble, and the cameras lose track of a few balls. When this happens the system will often make a poor guess as to what the motion really ought to be. This is fixed by a human in the post-processing phase where they are looking at the skeleton of a character and watching it move through its range of motions.

A large proportion of the outsourced motion capture work is performed by House of Moves using the standard Vicon cameras and its Deva system for post-processing. However, many publishers and some of the largest independent developers have their own systems.

One of the more interesting motion capture studios is Giant. Giant uses a fundamentally different motion capture system. Instead of using the expensive proprietary Vicon cameras, Giant employs 18 or so regular black-andwhite security-type video cameras. These cameras then feed the real-time data into Giant’s processing software called Motion Reality. One of the appeals of Giant’s system is that before you capture any motion data, you provide your character’s model, textures, and skeletal structure to Giant for preprocessing. This preprocessing involves using some neat-o biometrically correct algorithms that learn the parameters of motion for your specific character. This provides two distinct advantages: first, when taking the actual motion capture shoot, instead of the director looking at a constellation of balls on the playback monitor, he is able to see the motion as applied to the actual character while in the motion capture studio, without waiting days for the data to be cleaned up and applied to the character. Second, because the biometrically correct algorithms are applied to the motion capture data in real time, you save yourself a lot of cleanup processing that occurs when balls go out of the camera’s view, due to the algorithm’s ability to extrapolate and interpolate where those missing balls ought to be.

So Giant’s system sounds like the best one to use, right? I honestly cannot give you a final answer. We have used both data from Giant, sourced from a motion capture session just for us, as well as some library footage from House of Moves. To our surprise, while Giant’s post-processing software was relatively easy to use, there was more cleanup involved than I expected for the advanced system. As for the House of Moves data, it was data that was about two or three years old by the time we were able to play with it, and it showed its age. The data was noisy and not all that cool feeling when applied to our models. I would have to say that both of these motion capture studios deserve consideration for your next project.

Planning Your Motion Capture Shoot
To be successful with motion capture I suggest you seek out your eventual motion capture vendor early in production to establish budget. Shop around, as one facility may be booked and another might be happy to sell time at a minimal margin. The motion capture studios tend to build their bid by counting the total number of moves and actors you are requiring. Next they classify your moves into several categories of difficulty from routine to very difficult. For example, routine moves would be running, shooting a weapon, and sneaking about. Moderately complex moves would involve light stunt work such as falling to a mat. From there, the shots can get pretty expensive, especially if you are hiring a stunt coordinator and stunt men to perform wire work.

You should prepare a list of all of the moves you need your characters to perform. Then meet with one or more of the motion capture studios and ask them how would they approach the project. Do they see room for collapsing some of the requested moves? Do they suggest some killer moves that you overlooked? Who do they suggest you hire as the motion actor?

One of the first things a motion capture studio will tell you if you are listening is that celebrities often make poor motion capture actors. For example, the going rate for a motion capture actor with modest stunt abilities is around $1,000 for the day. Some projects have spent $500,000 capturing the motion of star athletes only to throw the data away because the motion was poor relative to what a motion actor is able to perform.

After you have your budget and animation plan, it is best to go back and work on your characters for a while and be sure you have worked out all of your technical requirements and that your game design is final (e.g., you know if you need climbing or swimming motions). Only then come back to the motion capture studio to perform the data collection. You will need to allocate at least three months in your schedule to allow the motion capture studio to perform a first-pass cleanup to the data and then turn over the data to your team for further refinement.

Best Use of Motion Capture
In my opinion, motion capture really shines in recording the subtle movements a human makes that are difficult to notice and thus difficult to get into your key-framing. Fortunately, to me, this means that aggressively acrobatic work for which Hollywood might use human performers and wires should instead be done by key-frames. I love to see motion capture used for the idle animations of the character.

We have amazing motion of the female protagonist for the upcoming Black9 stretching and limbering up for battle wow! And on the sublime side of the spectrum, it should be trivial to key-frame simple walks and run cycles. In the future I expect the software side of motion capture to make large strides; soon I believe the data will just drop in, and in the end motion capture will provide us with amazingly quick and amazingly good motion for our characters.

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