Game Development Reference
Apply the Echo effect to the stair jump PRECOMP layer in the
stair jump composition. The default results in this case don't look
all that great. To get a better idea of what Echo is doing, change
the Echo Time (seconds) value to
0.35 and change the Echo
Operator value from Add to Minimum. Also, take the Number of
Echoes to 8. Then you'll see what's really going on here (Fig. 19.2).
Figure 19.2 After applying
the Echo effect, we can see a
composite of multiple frames from
The Echo effect creates echoes in time by blending consecutive
frames together into one composite. This creates a visual “echo”
as the frames ripple into one another. Echo works well for those
times when you want to really exaggerate an action in video, and
slow motion just doesn't pack a big enough punch. It can also cre-
ate visually interesting motion graphics because the echo effect
creates a trail. In this example, Paavo's stair jump was in a beauti-
ful and natural arc, which looks awesome when echoed.
The Echo Time (seconds) parameter determines where, in
time, that the echoes come from. A negative value will create the
echoes from the past, and a positive value will create echoes from
the future. Remember that this value is the time between echoes
in seconds not frames. Figure 19.3 shows the Echo Time value
at −0.15, which is much shorter than what we saw in Fig. 19.2.
Notice how the echoes are now much closer together.
In Fig. 19.4, I've adjusted the Echo Time value to a positive
number. Both Figs. 19.3 and 19.4 show the exact same frame.
Thus, we see how negative values take previous frames to make
echoes, which causes the current frame to be the beginning of the
trail. A positive value causes echoes to be from upcoming frames,
which causes the current frame to be the caboose in a choo-choo
train of echoes.
Where Won't Echo
The Echo effect
only works on
layers that change
over time, but the motion
must be either rendered or
precomposed. Still images
that are animated in the
current composition won't do
much with the Echo effect.