Cook Book

Working Directory

Mon, 09 Jan 2012 20:05:40 +0100

Howdy. Just thought I'd share this snippet of a code with you guys. Enter this into the "onScriptLoad" of the project setting to automatically set the working directory to where the nuke file is located. This probably only works in Windows, so if someone gets working versions for the other OS, that would be great.

os.chdir(nuke.root().name()[0:nuke.root().name().rfind("/")])

List of Nuke Flags

Wed, 22 Jun 2011 00:28:51 +0100

"""
flags.py
 nuke flags for easy access from /include/DDImage/Knob.h
 These are updated for nuke 6.2 with added comments. Flags not in 6.1 are 
 READ_ONLY, GRANULARY_UNDO, NO_RECURSIVE_PATHS
 comments taken from Documentation/NDK/Plugins/namespaceDD_1_1Image.html#426fa024992892aa333e53b4e19109b5
"""

# General flags (must not intersect any class-specific flags):
# Values that work for any knob:
DISABLED            = 0x00000080    # DISA...

Creating a new menu for Custom Gizmos

Sat, 19 Mar 2011 06:46:23 +0100

I had TONS of trouble trying to figure out how to make a menu, so here is my tutorial. (Keep in mind, this is a tutorial for super ultra mega beginners) Be SURE you read the directories carefully during this tutorial!

What we will do: We will add a new menu to your "Nodes" menu. This will make your custom gizmos easier to access.

First, we need to create some directories and files.

Navigate to Nuke x.x/plugins/ (My directory is: /usr/local/Nuke6.1v3-32/plugins/) (sometimes Nuke x.x...

Creating a new menu for Custom Gizmos

Sat, 19 Mar 2011 06:39:40 +0100

What we will do: We will add a new menu to your "Nodes" menu. This will make your custom gizmos easier to access.

First, we need to create some directories and files.

Navigate to Nuke x.x/plugins/ (My directory is: /usr/local/Nuke6.1v3-32/plugins/) (sometimes Nuke...

Creating a new menu for Custom Gizmos

Sat, 19 Mar 2011 06:38:40 +0100

What we will do: We will add a new menu to your "Nodes" menu. This will make your custom gizmos easier to access.

First, we need to create some directories and files.

Navigate to Nuke x.x/plugins/ (My directory is: /usr/local/Nuke6.1v3-32/plugins/) (sometimes Nuke...

Verbose to super verbose python trace debugging

Sun, 06 Mar 2011 22:39:27 +0100

Sometimes, verbose just isn't enough. There are a couple options:

1st level:

In your nuke home dir (assuming you haven't changed it, ~/.nuke on OSX and Linux - I don't know Windows), add or modify the init.py file by adding the line:

import callbacksTrace

This prints out every callback nuke makes. There are a lot of them!

2nd level (super verbose):

If you want to get tons more information that you'll probably ever need, but might just help you find or discover that one stupi...

Random Number Generator

Fri, 18 Feb 2011 22:11:30 +0100

A quick expression to generate numbers such as the gain value of a grade.

Either of these values will generate a value from 0 to 1.

random() or random(frame)

if you want to have the values from 0 to 2

2*random()

For generating from 1 to 2

1+random()

Some Flags

Wed, 01 Dec 2010 16:35:14 +0100

Using flags can be frustrating because not all flags are easily accessed or documented. Create a flags.py file and you have a simple way to easily get at them. Thanks to Nathan and Dee for the tip on where to find them. I'm not sure what context you would use all these or if they are all valid from within python, but the flags I've used from here all work.

"""
flags.py
...

Adding a Gizmo Icon
Mon, 30 Aug 2010 18:16:05 +0100
Why have a normal gizmo when you can spice it up with a flashy icon that shows up in your GUI? Just add this line to your .gizmo file, as the first line in your gizmo.

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Gizmo {
icon /the/location/of/your/gizmoimage.png

The .png file should be manageable, I use an image size of 90x66 pixels, and set up the image as a transparent .png file.
...

write nodes filename from topmost read
Mon, 30 Aug 2010 13:34:43 +0100
if you need your output file named exactly like your input file then use a little TCL expression in the file knob of the write node
suggestion your filename convention is like: //path/to/file/filename.pattern.ext
then:

[lindex [split [lindex [split [knob [topnode].file] .] 0] /] end]

will give you back just the "filename" part of the original read node
if you want to write to same folder as the original file but with a new filename extension you could use:

...

Using nuke.animation without tearing your hair out
Fri, 27 Aug 2010 19:37:25 +0100
This is quite possibly the most stubborn Nuke Python function I've ever encountered, and it took me a lot of poking and prodding to get it worked out, so I figured I should spread the knowledge around.
nuke.animation is the Python equivalent of (/wrapper for?) the TCL "animation" command. It allows you to perform operations on animation data, including the "Generate..." command found in any knob's "Edit" menu. This is the main reason I became interested in it in the first place, as I was writing...

Getting correct format and frame range if QuickTime movie, added via Python
Mon, 16 Aug 2010 13:09:24 +0100
If you want to add a QuickTime movie to the DAG pythonically, here's a trick for making sure you get the correct format and frame range.
(setValue on the file knob after a node has been created does not work as expected)

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filepath = myMov.mov
nuke.createNode("Read", "file ")

...

Techartists.org Python Portal
Thu, 12 Aug 2010 17:51:42 +0100
Some very useful information and some recipes:
http://tech-artists.org/wiki/Portal:Python

hotkey for toggling depth in viewer
Tue, 10 Aug 2010 21:13:19 +0100
Here is an example of how to add a hotkey to toggle the viewer' layer (aka channel set) to depth and back.
First we get the currently active viewer (in case there are mutliple ones in the current layout):

curViewer = nuke.activeViewer()

This returns the viewer window, but since the knob that sets the layer is just a regular knob attached to the viewer node, we need to get the actual node object from the viewer window:

...

Checking if a node is a gizmo
Mon, 09 Aug 2010 02:04:25 +0100
There are several ways to find if a certain node is a gizmo or not in Nuke. Here is a list of the most common ways to achieve that and their respective pitfalls if any.
Method I
This method basically checks for the gizmo_file knob on a node which is a knob that should only be present in nodes that are gizmos. The downside of this method is that if a user happens to add a user knob named gizmo_file to a node or group for some mysterious reason these will be listed as gizmos even though...

Detecting if a Node's Input has an Alpha Channel
Fri, 06 Aug 2010 19:36:11 +0100
The following expressions will check if the first input of a Node has a channel beginning with an "a". Obviously not 100% foolproof, but should get you started.
TCL Expression:

[string first ".a" [channels [input this 0]]]>-1

Python Expression:

[python "len(\[n for n in nuke.channels(nuke.thisNode().input(0)) if n.find(\".a\") != -1])>0"]

...

Random Frames from Read node
Fri, 06 Aug 2010 11:07:38 +0100
If you want to generate random frames from your current read node :
Pace a FrameHold node below your read node
Then goto first frame:- edit expression and place this code

viewerNode = curViewer.node()

int( random(frame) * (last_frame-first_frame+1) + first_frame ) )

...

AnimationCurve and AnimationKey objects
Tue, 20 Jul 2010 18:56:13 +0100
AnimationCurve Objects
AnimationCurve objects contain the animation data of a given animated knob, and can be accessed using a knob’s .animation() or .animations() methods.

NOTE: AnimationCurves can be created manually using Python, but for the purposes of this article, we will assume they all come from pre-animated knobs.

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g1 = nuke.toNode("Grade1")
gBlack = g1['blackpoint']
anim = gBlack.animation(0)
print anim

Here is the curve in questi...

Notes for Python for Artists - Python Panel UI video tutorial
Mon, 19 Jul 2010 01:12:42 +0100

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import re
class SearchReplacePanel( nukescripts.PythonPanel ):
def __init__( self ):
nukescripts.PythonPanel.__init__( self, 'Search and Replace', 'com.ohufx.SearchReplace')
# CREATE KNOBS
self.nodesChoice = nuke.Enumeration_Knob( 'nodes', 'Source Nodes', ['all', 'selected'])
self.searchStr = nuke.String_Knob('searchStr', 'Search fo...

Knob Animation and Python: A Primer
Thu, 08 Jul 2010 06:27:04 +0100
Interact with animated knobs and animated curves using Python.

Enter the Matrix Knob
Mon, 05 Jul 2010 08:13:42 +0100
A new feature in Nuke 6.1 is the exposed matrix knob on all 3D nodes that allow a transform (such as ReadGeo, Axis, Camera etc). This contains all the transformation data for the node in a 4x4 matrix expressed as homogenous coordinates.

Local Data and World Data

The transformation data is displayed as a local matrix and a world matrix. The local matrix contains the local transform data and reflects the values you have set in the regular transform knobs, however you can override them...

Notes for Python for Artists - Simple User Interfaces video tutorial
Mon, 05 Jul 2010 02:08:38 +0100
Nuke has pretty simple python commands that let you create simple user interfaces - without having to dive too much into python panels.

Print a pop up mesage:

nuke.message ( 'yay' )

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txt = str( len( nuke.allNodes() ) )
nuke.message( txt + ' nodes in the script')

Nuke.display method:

Nuke.display uses four arguments (s,o,t,w), explanation from running help (nuke.display) :

Creates a dialog box showing the result of a...

Calling Python from an expression
Sun, 04 Jul 2010 09:45:18 +0100
You can easily call Python methods from within expressions, similar to calling Tcl expressions from Python via nuke.tcl()
To do this, you use the "python" Tcl method, for example:

[python nuke.thisNode().metadata().keys()]

While this is mostly straight-forward, there are a few things to be aware of..
Square brackets in the Python expression clash with Tcl's syntax, or should either be escaped:

[python nuke.thisNode().metadata()\['input/filename'\]]

..or enclose t...

Dealing with NaN pixels
Sun, 04 Jul 2010 08:33:38 +0100
Here's an approach to dealing with the occasional NaN pixel that can for example crop up when outputting through the ScanlineRender node.
So what does it look like and why is it bad? On the left, the pixel sampler has selected a single NaN pixel being output through the ScanlineRender node and you can see that the information being displayed for that pixel is "nan" in each channel. And on the right is with VectorBlur added:

As you can see any kind of filtering will turn up as nast...

Use of expressions to modify animation curves
Sun, 04 Jul 2010 03:04:35 +0100
Timing changes can be quite a headache in most compositing packages.
Here's a few cases where the use of expressions can be of great help when dealing with time modifiers (frame holds, time offsets, time warps…)

1- Freezing an animation to a certain frame (FrameHold)

The syntax curve(frame) is one of the simplest and yet most useful ways to handle time within an expression. It means "take the value of this animation (curve), at this frame".
This can be used on any animated knob, but it's mo...

External Recipes
Thu, 01 Jul 2010 09:39:42 +0100
This is a great source for python snippets:
http://code.activestate.com/recipes/langs/python/

Switching Nodes with $gui variable
Mon, 14 Jun 2010 10:00:22 +0100

Switch node states or node tree branches automatically between GUI and render use with the $gui variable

Have a slow operator or process in your script that you want to be off when working but on when you send it to the farm or render locally via the command line? Having trouble remembering to switch these functions on? Or do you want to have read nodes with local paths / server paths that switch automatically when sent to a farm?
Now you can!
With the $gui expression. In the example below I...

setting context to node, knob or curve object
Mon, 14 Jun 2010 00:27:34 +0100
I often need to run code from within a group or gizmo instead of the top level (so nuke.allNodes() would return all nodes in a group rather than the top level for instance).
For groups I used to doe the ol' future import thingy:

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from __future__ import with_statement
with nuke.toNode( 'MyGroup' ):
print nuke.allNodes()

However, this won't work with gizmos:

Here you can use nuke.runIn() like so:

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def getAllNodes():
...

Getting the index context of a Knob
Fri, 11 Jun 2010 06:01:42 +0100

Scope:
There seems to be no Knob python method to get the context of a specific index inside a knob with multiple values (like an XYZ_Knob).

nuke.thisKnob() would get you the knob something is executed from, but not the index within the knob.

If, for example, you call a command in the Animation menu by right clicking on translate.y, or box.r, you'll only get the translate or the box knob, but not the subfield inside it.

However, The "animations" command in TCL does see...

value vs knob command
Sat, 05 Jun 2010 10:39:53 +0100
The simplicity of tcl's command based nature makes it nice and easy to use in Nuke's text knobs, such as labels (you can actually use tcl that way in pretty much any knob in Nuke that can take an expression).
The value and knob commands in particular are very handy to show node properties in the DAG.
In a node's label, simply type the following:

[value <knob name>]

Here is an example for the exposure node's "mode" knob:

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[value mode]
...

transformThis - example for smart node creation
Sat, 05 Jun 2010 00:59:38 +0100
Here is simple recipe for your menu.py, to make a hotkey that creates a normal Transform node for 2D nodes (just like th default 't' does), but if a 3D node is selected, it will create a TransformGeo node instead:

To find out if the selected node is a 3D node, I usually just check for a knob that 2D nodes never have. Let's use the 'render_mode' knob:

'render_mode' in nuke.selectedNode().knobs()

This returns a boolean (True or False) so we can use ...

Smoothing Animation Curves
Thu, 03 Jun 2010 12:00:15 +0100
Smoothing an animation curve can be done through the animation curve's “Edit/Filter” option.
However, this will move the original keyframes which seems a little destructive and doesn't allow a nice fine tuning workflow (other than jumping up and down on the undo button and trying again with a different value).

So here is an expression based solution that uses a user knob value to smooth the curve “live”:

In my Tracker node I have this animation curve:

I have also created two floating poin...

SwitchMatte
Sun, 30 May 2010 10:09:09 +0100

create whatever nodes you need for a certain effect. I.e. let's build Shake's SwitchMatte real quick:
select only the node that should be part of the effect and go to Other/Group (or cmd/ctrl + g or ).

The selected nodes will be tugged away into a group node. No worries, you can always open up the group to get to the nodes if you need.
To quickly build an interface for your group node to control the internal nodes, right click anywhere into the Group node's panel and chose 'Manager...

inrange - Check if a Frame is Within a Certain Range
Sun, 30 May 2010 07:45:23 +0100
Checking whether a certain frame or number is within a given range is often needed, and often resulting expressions are unnecessarily complex. Here is a simple solution:

This will get you the script's current frame:

frame

this will return true if the current frame is between 1 and 10 (inclusive):

inrange( frame, 1, 10 )

The latter is handy in nodes' disable knob to switch them on and off depending on a frame range:...