Datasheet
Motion Capture 17
systems. Until these are capable of delivering a convincing human performance, we still
need to rely on motion capture for the ultimate in photorealism.
As we mentioned at the beginning of the chapter, it’s important to know where your
motion-capture data comes from. You can use material downloaded from the Internet,
but it oen requires a lot of work and in the end produces less than adequate results. To
use motion capture to its fullest potential, you must have complete control over every
aspect, from the actor to the data that the motion capture outputs. With that said, more
and more websites oer motion-capture data. Using this data can save you a tremendous
amount of work, and the data is relatively cheap if not free.
Project: Motion Test
e Jack character is weighted, but you don’t know how he’ll perform. To test his abili-
ties, you can apply downloaded motion-capture data to his skeleton. e data used in this
project is from Carnegie Mellon University’s Graphics Lab. ey have a larger motion-
capture database that you can access at http://mocap.cs.cmu.edu/. In addition, they have
numerous other resources like converters and documentation. Follow these steps:
1. Open the mocap_v01.ma scene from the chapter1\scenes folder on the DVD. The scene
contains the character’s geometry weighted to his skeleton. The geometry and skel-
eton have been assigned to respective layers.
A second skeleton is in the scene: it’s signicantly larger than Jack’s skeleton
and has captured motion of an exercise routine. It’s assigned to a layer called
MOTION_CAPTURE.
2. Open the Outliner, and select the root node. Group this to an empty group node by
pressing Ctrl+G. Rename the group1 node mocap_GRP.
3. Select mocap_GRP, and scale it uniformly to the approximate size of Jack; 0.03605 is
good (see Figure1.21).
Make a note of the scale you end up using; it can be used for all the motion cap-
ture done with the same actor. Later in the chapter, you’ll apply dierent motion
from the same actor.
4. Turn o the visibility on the body layer.
5. e group node is mainly needed for scale. You can also use it to oset the skeleton.
You want to match the root joint of the motion-capture skeleton to Jack’s skeleton.
Before you can do this, you need to make sure you’re at the default skeletal pose for
both skeletons. In the Outliner, select the root node on the motion-capture skeleton.
e timeline should ll up with red keyframes. Change the start time to –100. Go to
frame –100, and then click the Step Forward One Key button on the timeline con-
trols. Doing so reveals that the rst keyframe is at –13. Change the timeline to match
the beginning and end.
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