Nuke; Python For Artists; Working with Nodes - Part 2A Video Lecture | Create Visual Effects with Nuke - Professional Skills

so let's go ahead and finish the script
we started in part 1 this time we'll
have a closer look at dealing with knobs
we will grab some information from the
preferences to build an output path we
will render the whole setup and pull the
rennet files back into nuke and then
delete all the unnecessary stuff and
finally wrap up the whole code to live
in a menu item so it's actually easier
to use so let's get started by selecting
that last node and simply running the
code from last time to see that
everything's still working and that
looks fine I don't need those two last
lines they were just for temp the first
thing I want to do is I want to change a
couple of knobs in the checkerboard node
so let's type the variable that holds
the checkerboard node and to access a
knob I simply type knob so we use the
node method followed by the knobs name
and once again I'm going to change the
box size knob so I'll type box size and
quotes and that returns the nodes knob
that has that name and what I want to do
is I want to set a value so I'll go set
value and the new values 150 so let's
run that line and watch the checkerboard
change its size if you don't really know
what knob name to use you can do a
couple of things you could pop up the
pedal and simply check the tooltip like
so or you could print the actual node
object like so and that will print a
Python dictionary which consists of
knobs and values so the knob names are
the keys and their respective values are
the dictionary values and that's a nice
ordered list to get an overview over the
knobs let's change the center line with
this time so once again I go check out
and instead of dot knob I'm going to use
an alternative method because we now
know that the node object is a
dictionary so i can use pythons ways of
dealing with dictionaries by simply
using square brackets
and the knob name that I'm after and
that will access the knob as well so I
can then go set value zero to get rid of
the yellow lines like so so those two
lines pretty much are interchangeable in
terms of how to access the knob this is
a bit more the bows but easier to read
and this one is a bit shorter so just
pick whichever one suits you best so
next we'll have a look at the
Preferences real quick to grab the cash
path and we'll be using that to build a
valid output directory so you can see
here if you hold your mouse pointer over
the disk cache knob like so that will
tell us the name is disk cache path will
access the preferences as if it was a
hidden node in fact it is a unique
hidden node so we can use the same
method we used in part one to access it
by name new code to node and its name is
actually preferences with a lowercase P
for some reason so that accesses the
preferences and what we want to do is
you want to access its knob and the knob
is called disk cache path as we just saw
on the tooltip and finally we don't want
to set a value this time around we just
want to read its value so we just type
value with an empty set of parentheses
and let's see if we did that right yeah
so this returns the value that is in
your disk cache pass norb in the
preferences let's store that in a
variable called temp der for example and
then build the entire path by adding a
file name I'm going to call the temp
pass the temp path should be whatever is
in tempter plus and then we'll just add
the file name but I'll put a slash there
to make sure we go into that temp
directory and then I'll just make up a
file name just like you would in a right
node rollo check rotal check there
followed by some frame padding and I'm
just going to run JPEGs so that should
create an evaluator output path next
we'll create a write node
sell some more space here so let's go
write equals new code nodes dot right
and the file knob should have the value
that lives in the variable temp path and
the right notes name should be temp
right close that and run those three
lines and that gives us a new right note
in the script and we already know how to
set its input from the first part right
set input there's only one pipe so
obviously it'll be index zero and that
should be connected to the merge node
like so