Game Engine Architecture

514 11. Animation Systems

11.4.4. A Simple Animation Data Format

Typically, animation data is extracted from a Maya scene fi le by sampling the

pose of the skeleton discretely at a rate of 30 or 60 samples per second. A sam-

ple comprises a full pose for each joint in the skeleton. The poses are usually

stored in SQT format: For each joint j, the scale component is either a single

fl oating-point scalar Sj , or a three-element vector Sj = [ Sjx Sjy Sjz ]. The rotation-

al component is of course a four-element quaternion Qj = [ Qjx Qjy Qjz Qjw ].

And the translational component is a three-element vector Tj = [ Tjx Tjy Tjz ].

We sometimes say that an animation consists of up to 10 channels per joint,

in reference to the 10 components of Sj , Qj , and Tj. This is illustrated in Fig-

ure 11.20.

Figure 11.19. A global clock approach can alleviate animation synchronization problems.

0123456789

Samples

Joint 0

T 0

Q 0

S 0

Joint 1

T 1

Q 1

S 1

...

yxz

yxz

w

yxz

... ...

Figure 11.20. An uncompressed animation clip contains 10 channels of fl oating-point data

per sample, per joint.