Flight frames for the missile art. The projectile advances this with its own elapsed
time, so a caller reads frame/frameOffset here instead of keeping a second
animation and an elapsed clock in step with the tween.
Optionalduration
duration?:number
seconds to cross the whole flight; overrides speed when both are given
Optionalspeed
speed?:number
world units per second; ignored if duration is given
Flight frames for the missile art. The projectile advances this with its own elapsed time, so a caller reads
frame/frameOffsethere instead of keeping a second animation and an elapsed clock in step with the tween.