Nuke; Python Essentials; Basic Workflow Commands - PartA Video Lecture | Create Visual Effects with Nuke - Professional Skills

so this tutorial is for artists that
don't really care that much about Python
but they do want to get some more
mileage out of customizing nuke beyond
the mains of what the Preferences pane
can offer so we'll have a look at a
couple of Python commands without going
too much into the scripting languages
properties and all that so don't freak
out too much I'll just try to give you
the tiniest bits of information you need
to really get a lot more out of
customizing nuke so first of all bring
up the script editor if you don't have
it up already you can grab that anywhere
in the interface and let's say when I
create a Bezier node I don't want it to
come up with the output knob set to RGB
a because usually I only wanted an alpha
Channel and I don't want it to override
red green and blue so the first not
default you want to set is the Bezier
knobs output knob and we want to set it
to alpha which will be this alpha layer
so let's do that the command we need for
this is called nuke knob default with a
capital D and in parentheses after that
we will give it a couple of arguments to
make it do what we needed to do so the
first argument is a string so you use
either single quotes or double quotes
and the first thing you want to type
here is the notes class in that case
it's called Bezier followed by a dot and
then followed by the knob name that we
want to change in this case it's the
output after that we'll do a comma and
then the second argument again is a
string so start with a quote and the new
value we want to use as a default value
is alpha because that's the name of the
layout we want to make the vision or
drawing too and then we'll go and
correct our typos here and after that
execute the script by either hitting
this button up here or you can also hit
control enter or command enter on a Mac
so after executing this not default
command creating a Bezier node will now
cause it to automatically draw into the
Alpha layer so we don't have to fill
with this anymore another knob default I
like setting is for the exposure node
which is in
Calla menu here and I like working in
f-stops so I like setting this guy here
to stops and I don't want to have to do
this all the time so let's let's set up
another knob default I'll bring up the
last command with this little arrow
button up here and just simply
copy/paste that because I'm lazy and
then swap this for the new note class
that we're now trying to set and you
might have noticed even though this guy
is called exposure in the menu the
actual note class is different
the first tab should give you a clue of
what the note class itself is if you're
not sure simply select the node and hit
I that will bring up an info viewer and
that will explicitly tell you the class
off that note that you need to use in
those Python an expression commands so
that's exp tool make sure you get the
lowercase and uppercase right and the
knob name is not adjust in but instead
if I hover my mouse pointer over it
its mode the first word in the tooltip
that is written in bold letters will
tell you what the actual nor blame is so
don't rely on the labels and don't rely
on the node names make sure you double
check the class and the knob name so
this guy is called mode so what we want
to type is exp tool dot mode and the new
value could be stops again upper case
and lower case is important and I forgot
to close my quote over here and I'll hit
command enter and create a new exposure
tool and you can see it's now set to
stops another thing I could have done to
use the value is simply use the index of
the list this is index zero one two and
three so instead of instead of assigning
the word stops we could have assigned
the index zero and that would work as
well so there you go a little something
that I like using on various nodes is to
make them draw certain values into the
node graph right here the way we can do
this is using the label and using a very
short TCL command which is simply called
value and have that evaluate
for the label so in this case I want the
exposure tool to draw the value of the
mode knob into the node graph so I'm
going to type value mode oops
with a space in between and if you put
this whole thing into square brackets it
will evaluate the script that it is and
will actually return the value of that
knob in the node graph so that's kind of
neat because you can see straight away
if that particular node is set to
densities light stops or sitting on and
if you can't be bothered to remember
this expression then this can actually
be a fully blown TCL expression and even
a Python command once again you can
simply set a knob default and
this again copy-paste will this time
will set a default for the label and um
this is gonna be our new knob default so
now once that's set we don't have to
worry about remembering that syntax and
everything should fall into place so now
here we go this is said to stops and
we've got the TCL script expression in
the label and we can happily forget the
syntax of it