Thinking about this now can help save valuable time during the capture session and minimise the amount of editing work required afterwards. You may not have the answers now, but it is worth beginning to consider it and make a note of any actions that will require further investigation. Also, don’t be afraid to rule out motion capture for actions you feel may be achieved more simply using hand animation.
How many performers will you need to perform the action or scene? If you have the budget, you could cast a different performer for every role or you may need the smae performers to play multiple characters. A shot involving background characters might need to be captured in 2 passes: one with the performers playing the main characters, then another with the performers playing the background characters. Whatever you do, do not try use a single performer to play every character. The money you think you’ll save will be lost in the performance and time spent fixing the actions in post (plus, it’s a horrible thing to do to a performer). Knowing the number of performers you’ll need for each action will help you plan how many performers you’ll need on each day of the shoot and how much this will add to your shoot costs.
What skills are needed to perform the action? Some actions may require specialist skills or abilities to perform them, either to the level you want or for safety reasons. Understanding what skills are required to perform the actions will help you hire the right performers and may also require you to cast multiple performers to play the same role.
What are the proportional differences between the performer and the character? Ideally the skeletal proportions of your performer and character will be about the same. The closer the skeletons match, the easier and more accuratly the mocap data will transfer and the less editing the actions will require. If there are scale differences between the skeletons, don’t forget to take this into account when creating props and laying out the scenery.
Is contact in the action necessary? Careful planning and understanding of all interactions can help reduce the amount of editing an action will require. Contact with themselves, other performers, props and the environment can all increase the amount of editing an action may require, especially if the performers and character have different proportions. Actions with very close proximity between performers can also affect a motion capture system’s ability to capture the action; these types of actions will need to be discussed with the motion capture company to make sure they are able to capture them or provide an alternative solution.
How much space does the action require? Try to estimate the amount of space required to perform the action, especially if it looks like it is going to cover more than a couple of meters in a single direction (don’t forget to include vertical as well as horizontal directions). The capture volume is defined by the space in which the motion capture system can detect the movements of the performer. If the amount of space required to perform an action is larger than the space within the capture volume, the system won’t be able to capture it. It may be possible to change the configuration of the capture volume to accommodate different actions, but this can be very time consuming. Another option, which would require careful planning, could involve breaking the action down in to separate takes that fit inside the volume, and then recombining them at the editing stage.
Where does everything go in the volume? You have a list of props and scenery items from your mocap shot list, but you also need to know exactly where they need to be placed, which direction they are facing, what order they are used in and how your character moves between them. For example, if your character gets out of a vehicle, picks up a prop and goes into a building, you will need to know which door they get out of, where the prop is, what direction they walk, which way the door to the building opens and everything everything in between. And don’t forget to factor in any scale difference between your performer and character when measuring the distances.
Does the action need specific scenery? Remember, the mocep volume is a big empty box you have to fill with imagination and objects. If you can’t mark it out on the floor with tape or make it with a few boxes, you’re probably going to need to get something built. Ideally any builds will be “mocap friendly”, meaning they won’t be solid enough to hide (occlude) all the markers (for optical), but will be solid enough to hold objects or withstand any impacts.
Does the action require specialist equipment? Beside the standard props and scenery requirements, an action may also require more specialised equipment for safety or performance reasons. This kind of equipment may have specific requirements in order to be set-up and used, and may also require qualified people to operate it. These kind of actions should be discussed with the motion capture company to make sure their facilities can accommodate the equipment and that it won’t compromise their ability to capture the action.
Does the action require specialist facilities or location? Motion capture stages are generally large empty spaces with a designated performance volume surrounded by motion capture cameras. Some actions may require the use of a specialist facility or location in order to be performed correctly. This is something you will need to discuss with the motion capture company as their system will need to be portable and capable of capturing at the alternative location.
Can the motion capture system capture the action? All motion capture systems have some kind of limitation that can restrict what they can capture, where they can capture it and the quality of the data they produce. If you are unsure of a systems limitations, try to arrange a test shoot or discuss the actions with a motion capture company to highlight any potential problems.
Sometime an action may require an audio track to take a cue from. This could be a dialogue or music the action needs to synchronise with. Make a note of the audio you will need on the shoot, so you don’t forget it. Also, make sure there will be a way to play it back in the mocap studio during the performance.
If you can, bring video reference with you to the shoot – and don’t forget to make sure you can play it back. Sometimes it’s easier to show the performer what you want them to do rather than try and explain it (make sure what you’re showing them is what you want them to do or very close to avoid confusion). You might also need their performance to match or link up with an existing one or contain some of the same mannerisms or characteristics.