Nuke; Python For Artists; Working with Nodes - Part 1 Video Lecture | Create Visual Effects with Nuke - Professional Skills

so let's actually write something useful
for production this time I want to write
a little tool that will enable roto
artists to quickly check their their
work in motion so we'll write something
that will add a promote node to the
currently selected node and merge the
result on top of a checkerboard and then
write that out to disk and then we'll
bring it back into a read node for
future reference and then clean up after
ourselves and restore the nuke script as
it was before the Python script was run
so let's have a look at how that works
first I want to access the last node in
the script which is busy a5 and since
nothing is selected at the moment I need
to access it by its name and we can do
this by using new code 2 node followed
by the name of the node we want to
access like so so if I select this and
run you can see that this returns the
node object of the node called Bezier 5
and if I wanted to select it in the node
graph I can simply go dot set selected
and set that to true running that line
will simply select a note that is called
Bezier 5 now we will assume that the
artist obviously selects a node for us
and then runs our script on it so the
first thing I want to do in the real
script that I'm about to write is to
store the current node selection and
I'll just use colonel equals nuke dot
selected node so this will return the
currently selected node and we'll save
it into the kernel variable for us to
play with later the next thing I want to
do is create a promote node and the
easiest way to do this is using nuke dot
create node followed by the node class
is a string as its argument and this
will mimic exactly how a node would be
created through the interface let's have
a look at that
so this will attach a promote note it
will actually connect it to the
selection it will take over the
selection in the node graph it will open
the panel it will auto place itself and
you will get all those things for free
using Create node now what if I didn't
want to open the note panel because I
find it quite annoying I can simply use
in panel equals false and that will
still deliver all the goodies but it
won't open the panel another thing that
is advisable to do is to create
variables and store the result of those
node creations in them so we can
actually access all the notes later on
that we created like so so for loop this
again and run this one more time we get
our pre mult but this time we still have
access to it through the Primo terrible
so if I now wanted to change the name of
it I could go pre mode set name and give
it a new name running that line will
rename our node now let's create a
checkerboard doing the same thing
Nuka dot create node checkerboard I
actually want to create check about two
because the other one is old and um this
time I want to assign a null value as I
create this and I can do this by using a
second argument again it's a string and
in fact this is a TCL list so
unfortunately the create node is a bit
of a hybrid between Python and TCL
anyway the way it works is you simply
use the knob name followed by the value
so let's say I want to change the
checkerboards book size to 100 I just
type box size space value and if I
wanted to assign more knob and value
pairs I would just go a space in the off
space value and so forth in this case
this is all I want so I close the quote
and once again we don't want the panel
to open
so we'll run this and that gives us our
checker board now again I forgot to
actually assign let's check about to a
variable so I'm kind of stuck now so
I'll assign that to a variable again and
now we can actually work with it let's
say we want to open the panel using a
new code shell we can now type that
variable into that new code show method
run that and we'll open the panel for
the checker board and we can see that
box size knob has been set to a hundred
on creation next we want to create a
merge node so once again we go a new
code create node merge and actually
again like the checker board - I want to
create the node merge - not merge merge
is the old merge merge - is the new
merge if you're not sure which class to
put in here simply create the node that
you're after in the interface and then
go to edit node and find the info viewer
or simply hit I in the node graph and
that will open a whole bunch of
information about the selected node and
a second line will tell you which class
to use in your Python script so once
again we want merge two and running that
once again will auto place it or to
connect and all that however in this
case because merge one will merge is a
multi input node it could connect A or B
depending on the user preferences so I
don't want to rely on user preferences
to understand which pipe is connected so
I'd rather do it manually so I know what
I get
so let's actually look at an alternative
way to create nodes and that's the new
code nodes package so to speak the nuke
nodes package will let you enter node
classes as a method so I can just type
that here without quotes and if I run
this with a checker board selected or
anything selected you'll see that this
will simply add the merge node somewhere
in the script without actually modifying
the existing nuke script in other words
this method will ensure you
breaking any pipe connections or
changing the current node selection and
it's a much more predictable way of
creating nodes but you will have to
everything manually another benefit of
this is that the argument list is
actually a proper pythonic syntax so I
can say I want the name to be temp merge
comma
I want the label to be something
whatever and so forth so that's a lot
cleaner than the argument list used for
new code create node and once again will
store the whole thing in a variable like
this and run it there we are now what's
left to do for us is to actually connect
the a and B pipes and in order to do
that we'll have a quick look at the
merge node using Python stir function to
list all the methods that are available
to us such as type dur and in
parentheses my node and running that
line will list all the methods available
to us if you type help instead of derp
you'll actually get more or less verbose
help text for all those methods you can
see we find the setname method in here
and the set selected method we used
earlier and we also find the set input
method which is exactly what I need to
connect inputs in Nuuk so let's get rid
of this and type merge dot set input and
the first argument for the set input
method is the pipe number you want to
connect with the rightmost pipe in the
node graph being index zero so let's
wire up the B pipe and we want to put
that against the checker board like so
and that connects our background and if
I copy that line and paste it and then
use index 1 which is pipe a and that is
supposed to be connected to the promote
node
that will create our script so let's
just quickly have a look at what we've
been doing
by using nuke don't connect viewer you
could not connect viewers a very similar
method to set input in that it takes a
pipe index first which is pipe 0 that is
buffer 1 in our interface and that is
meant to connect to the merge node and
now we can actually see what's going on
and to play the whole thing we can use
nuke dot active viewer don't play and I
want to play forward so I'm giving it a
1 if I wanted to play backwards I could
give it a 0 and of course I can stop the
whole thing as well like that so this is
pretty much all for part 1 and part 2
we'll have a look at how to render the
whole setup through a write node we will
look at bringing in the rendered
sequence into a read node and then
cleaning up after ourselves by deleting
all the nodes we created and also we'll
stuff the whole thing into a menu and
assign a hotkey