Game Engine Architecture

532 11. Animation Systems

Targeted movement is just a special case of one-dimensional LERP blend-

ing. We simply straighten out the circle on which the directional animation

clips were placed and use the movement direction angle θ as the param-

eter b (with a range of –90 to 90 degrees). Any number of animation clips

can be placed onto this blend range at arbitrary angles. This is shown in Fig-

ure 11.33.

11.6.3.2. Simple Two-Dimensional LERP Blending

Sometimes we would like to smoothly vary two aspects of a character’s motion

simultaneously. For example, we might want the character to be capable of

aiming his weapon vertically and horizontally. Or we might want to allow our

character to vary her pace length and the separation of her feet as she moves.

We can extend one-dimensional LERP blending to two dimensions in order to

achieve these kinds of eff ects.

Clip A

b 0 b 1 b 2 b 3 b 4

Clip B Clip C Clip D Clip E

b

12

1

bb

bb

−

=β −

Figure 11.32. A generalized linear blend between N animation clips.

Figure 11.33. The directional clips used in targeted movement can be thought of as a special

case of one-dimensional LERP blending.