Nov 12 2014

Feedback TOP tutorial.

The Feedback TOP. TouchDesigner 088. 2014.
The Feedback TOP can produce amazing 2D trails, blooms, and other time-based visual efefcts. For beginners, it can be extremely difficult to understand. This tutorial is designed to help you grasp the specific TOP network requirements to get a feedback loop working.

1
00:00:00,200 –> 00:00:02,867
Let’s examine the feedback TOP.

2
00:00:02,867 –> 00:00:11,533
In its simplest form, the
feedback TOP loop consists of 3
operators.

3
00:00:11,533 –> 00:00:14,867
First, we begin with an image to
operate on.

4
00:00:14,867 –> 00:00:22,267
In order to see the effect of
the feedback loop, we need some
sort of animation here.

5
00:00:22,267 –> 00:00:25,367
Next, we need a feedback TOP.

6
00:00:25,367 –> 00:00:36,033
The feedback TOP needs to send
it’s output to an operator that
can combine itself, and the
original image.

7
00:00:36,033 –> 00:00:44,233
The feedback TOP must then
reference that final operator,
which will close the feedback
loop.

8
00:00:44,233 –> 00:00:50,600
In order to see the effect of
the feedback loop, we must
animate the original TOP.

9
00:00:50,600 –> 00:00:57,267
We start with a circle TOP, and
control it’s center position
with a 2D slider.

10
00:00:57,267 –> 00:01:04,400
We normalize the initial slider
values to a range of -.5 to .5.

11
00:01:04,400 –> 00:01:07,400
This becomes the circle’s UV
offset.

12
00:01:07,400 –> 00:01:08,433

13
00:01:08,433 –> 00:01:11,733
Now, I’ll move the 2D slider.

14
00:01:11,733 –> 00:01:17,633
As you can see, the effect of
the feedback loop is very
apparent.

15
00:01:17,633 –> 00:01:25,233
We can use the reset button on
the feedback TOP parameter panel
to clear the effect.

16
00:01:25,233 –> 00:01:27,800

17
00:01:27,800 –> 00:01:32,700
This network illustrates a more
comprehensive feedback loop.

18
00:01:32,700 –> 00:01:43,033
It’s basically a duplicate of
first network, with additional
downstream TOP operations being
performed on the feedback TOP.

19
00:01:43,033 –> 00:01:50,300
The first TOP is a luma level
TOP. It performs a very
important function in the
feedback loop.

20
00:01:50,300 –> 00:02:00,667
By reducing the opacity of the
feedback TOP, each successive
copy in the feedback loop will
fade a little bit more.

21
00:02:00,667 –> 00:02:14,967
As you can see, each slight
transformation we successively
apply to the feedback network
causes the feedback effect to
change or shift with each
repeating copy.

22
00:02:14,967 –> 00:02:23,267
A small shift or change will
gradually grow or shrink over
the life of the feedback loop.

23
00:02:23,267 –> 00:02:31,867
It’s possible to create several
different types of feedback
behaviors, including color
shifts over time.

24
00:02:31,867 –> 00:02:34,067

25
00:02:34,067 –> 00:02:41,767
Now that the feedback loop is
ready, we can use the 2D slider
to see the effects of our
settings.

26
00:02:41,767 –> 00:02:44,133

27
00:02:44,133 –> 00:02:55,800
The concept of feedback loops in
Touch Designer is very powerful,
and you can create very
surprising effects by
experimenting with effect
chains.

28
00:02:55,800 –> 00:02:57,800

Posted In
Tagged