Expression Node

I created this small guide because during my period of work at Trixter, I learnt how powerful the Expression node can be. So I tried to collect as many tools as possible. In the links below you can find all the websites where I found info and code. I would also like to thank the Trixter comp team for the incredible workshops about the Expressions.

You can download the folder from the link below:
Download from Nukepedia

HOW TO INSTALL IT?

Installing the package is really easy, because all the paths and folders are already set up.

1. Extract the folder from the .zip file
2. Drag and drop the folder into your .nuke folder
#path would be something like this:

#Linux: /home/login name/.nuke
#Mac OS X: /Users/login name/.nuke
#Windows: C:\Users\user name\.nuke

Expression Node Collection for Nuke - HOW TO INSTALL IT?

3. Add this code to your init.py file
Expression_path = "/Users/yourPath/.nuke/Expression"
nuke.pluginAddPath(Expression_path)

4. Run Nuke

New on this site · Math in Nuke

The maths behind these Expression nodes, explained page by page with labs:

Expressions & Curves – lerp, smoothstep, waves and noise for any knob
Merge & Premultiplication – what over really computes, and what happens when alpha leaves 0–1
The Math of Keying – Keylight, IBK, ChromaKeyer and the other keyers, measured
Vectors – normals, position and motion passes, dot and cross product

Useful Links

Overview

You will find some text called

Show/Hide node script

Click on it to show/hide the script of each node. Copy and Paste it in the Node Graph of Nuke! If you want the whole collection, download it from Nukepedia at the link above

Click on the links below to go directly to the section you want:

Expression Node Collection for Nuke - Show/Hide node script

01. Creations

In this first category you can create different elements only with the Expression Node. Here you will find some of the tools in the collection.

RANDOM
Create random colors for every pixel/every frame

Show/Hide node script

set cut_paste_input [stack 0]
version 10.5 v2
push $cut_paste_input
Expression {
 expr0 random
 expr1 random
 expr2 random
 expr3 random
 name Random_every_pixel
 selected true
 xpos 1125
 ypos 232
}
Expression {
 inputs 0
 expr0 random(frame)*random
 expr1 random(frame)*random
 expr2 random(frame)*random
 expr3 random(frame)*random
 name Random_every_frame
 selected true
 xpos 1123
 ypos 189
}

LINES
Create horizontal/vertical lines with different width and smoothness.

CIRCLES

RADIAL

POINTS
Create points with different color and opacity. Combined with a Convolve Node and a Shape you can create different types of walls.

Show/Hide node script

set cut_paste_input [stack 0]
version 10.5 v2
push $cut_paste_input
Expression {
 expr0 fmod(x,offsetX)==0?fmod(y,offsetY)==0?random_colors?random:value:0:0
 expr1 fmod(x,offsetX)==0?fmod(y,offsetY)==0?random_colors?random:value:0:0
 expr2 fmod(x,offsetX)==0?fmod(y,offsetY)==0?random_colors?random:value:0:0
 expr3 fmod(x,offsetX)==0?fmod(y,offsetY)==0?random_colors?1:value:0:0
 name Points
 selected true
 xpos 396
 ypos -174
 addUserKnob {20 User}
 addUserKnob {7 value}
 value 1
 addUserKnob {6 random_colors l "random colors" -STARTLINE}
 random_colors true
 addUserKnob {7 offsetX R 0 100}
 offsetX 200
 addUserKnob {7 offsetY R 0 100}
 offsetY 200
}

BRICKS
Wall of bricks that you can create combining Expression and UV Map Nodes

Show/Hide node script

set cut_paste_input [stack 0]
version 10.5 v2
push $cut_paste_input
Expression {
 temp_name0 dimension_width
 temp_expr0 size*width_brick
 temp_name1 difference_size
 temp_expr1 size
 temp_name2 dimension_height
 temp_expr2 size
 expr0 "floor(y/size)%2 == 0? (x%(dimension_width*scale))/(difference_size*width_brick*scale) : ((x+offset)%dimension_width)/(difference_size*width_brick)"
 expr1 "floor(y/size)%2 == 0? (y%dimension_height)/(difference_size) : ((y)%dimension_height)/(difference_size)"
 name bricks
 selected true
 xpos 131
 ypos -105
 addUserKnob {20 User}
 addUserKnob {7 size R 0 200}
 size 216
 addUserKnob {7 offset R 0 100}
 offset 132
 addUserKnob {7 scale R 0 6}
 scale 1
 addUserKnob {26 ""}
 addUserKnob {7 width_brick R 0 5}
 width_brick 1.3
 addUserKnob {3 random_value l INVISIBLE +INVISIBLE}
 random_value 61
}

TRUNC
Round to the nearest integer not larger in absolute value

02. Alpha

Some of the operations you can do with the Alpha channel:

03. Pixel

In this third section, Pixel, we are going to work with Pixels. This part is really good for Tech Checks of your shots.

ABSOLUTE VALUE
Returns the absolute value of the floating-point number x

Show/Hide node script

set cut_paste_input [stack 0]
version 10.5 v2
BackdropNode {
 inputs 0
 name BackdropNode3
 tile_color 0x7171c600
 label ABS
 note_font_size 42
 selected true
 xpos -311
 ypos -252
 bdwidth 274
 bdheight 394
}
StickyNote {
 inputs 0
 name StickyNote1
 label "Return the Absolute value (always positive values)"
 selected true
 xpos -290
 ypos 98
}
Constant {
 inputs 0
 color 1
 name Constant2
 selected true
 xpos -218
 ypos -143
}
Multiply {
 channels rgba
 value -1
 name Multiply1
 label -1
 selected true
 xpos -218
 ypos -30
}
Expression {
 expr0 abs(r)
 expr1 abs(g)
 expr2 abs(b)
 expr3 abs(a)
 name ABS
 selected true
 xpos -218
 ypos 47
}

INF NAN NEGATIVE PIXELS
Find the infinite, NaN and Negative Pixels in your image.

Show/Hide node script

set cut_paste_input [stack 0]
version 10.5 v2
BackdropNode {
 inputs 0
 name BackdropNode17
 tile_color 0x7190c6ff
 label check
 note_font_size 42
 selected true
 xpos 347
 ypos -340
 bdwidth 279
 bdheight 237
 z_order 1
}
push $cut_paste_input
Dot {
 name Dot1
 selected true
 xpos 478
 ypos -269
}
set N1e6e4590 [stack 0]
Expression {
 expr0 isinf(r)?1000:0
 expr1 isinf(g)?1000:0
 expr2 isinf(b)?1000:0
 expr3 isinf(a)?1000:0
 name Expression17
 label INF
 selected true
 xpos 357
 ypos -210
}
Blur {
 channels rgba
 size 20
 name Blur204
 label "\[value size]"
 selected true
 xpos 357
 ypos -172
}
push $N1e6e4590
Expression {
 expr0 isnan(r)?1000:0
 expr1 isnan(g)?1000:0
 expr2 isnan(b)?1000:0
 expr3 isnan(a)?1000:0
 name Expression16
 label NAN
 selected true
 xpos 504
 ypos -215
}
Blur {
 channels rgba
 size 20
 name Blur205
 label "\[value size]"
 selected true
 xpos 504
 ypos -169
}

04. Keying and Despill

Some useful tools for the Keying and Despill operations.

BLUE DESPILL
Different despill techniques for blue screen.

Show/Hide node script

set cut_paste_input [stack 0]
version 10.5 v2
ColorWheel {
 inputs 0
 gamma 0.45
 name ColorWheel3
 selected true
 xpos 1466
 ypos -179
}
Dot {
 name Dot3
 selected true
 xpos 1500
 ypos -66
}
set N2eb56c50 [stack 0]
Expression {
 expr2 b>(g+2*r)/2*LimitPercentage?(g+2*r)/2*LimitPercentage:b
 expr3 b-(2*r+g)*LimitPercentage/2
 name DoubleRedAve2
 tile_color 0xff01
 selected true
 xpos 1688
 ypos 63
 addUserKnob {20 User}
 addUserKnob {7 LimitPercentage l "fine tune" R 0.5 1.5}
 LimitPercentage 1
}
push $N2eb56c50
Expression {
 expr2 b>(g+r)/2*LimitPercentage?(g+r)/2*LimitPercentage:b
 expr3 b-(r+g)*LimitPercentage/2
 name Average
 tile_color 0xff01
 selected true
 xpos 1576
 ypos 64
 addUserKnob {20 User}
 addUserKnob {7 LimitPercentage l "fine tune" R 0.5 1.5}
 LimitPercentage 1
}
push $N2eb56c50
Expression {
 expr2 b>(2*g+r)/2*LimitPercentage?(2*g+r)/2*LimitPercentage:b
 expr3 b-(r+2*g)*LimitPercentage/2
 name DoubleGreenAve
 tile_color 0xff01
 selected true
 xpos 1466
 ypos 63
 addUserKnob {20 User}
 addUserKnob {7 LimitPercentage l "fine tune" R 0.5 1.5}
 LimitPercentage 1
}
push $N2eb56c50
Expression {
 expr2 b>g*LimitPercentage?g*LimitPercentage:b
 expr3 b-g*LimitPercentage
 name GreenLimitsBlue
 tile_color 0xff01
 selected true
 xpos 1354
 ypos 63
 addUserKnob {20 User}
 addUserKnob {7 LimitPercentage l "fine tune" R 0.5 1.5}
 LimitPercentage 1
}
push $N2eb56c50
Expression {
 expr2 b>r*LimitPercentage?r*LimitPercentage:b
 expr3 b-r*LimitPercentage
 name RedLimitsBlue
 tile_color 0xff01
 selected true
 xpos 1246
 ypos 63
 addUserKnob {20 User}
 addUserKnob {7 LimitPercentage l "fine tune" R 0.5 1.5}
 LimitPercentage 1
}

GREEN DESPILL
Different despill techniques for green screen.

Show/Hide node script

set cut_paste_input [stack 0]
version 10.5 v2
ColorWheel {
 inputs 0
 gamma 0.45
 name ColorWheel2
 selected true
 xpos 869
 ypos -127
}
Dot {
 name Dot2
 selected true
 xpos 903
 ypos -11
}
set N2eb50ba0 [stack 0]
Expression {
 expr1 g>(b+2*r)/3*LimitPercentage?(b+2*r)/3*LimitPercentage:g
 expr3 g-(r+b)*LimitPercentage/2
 name DoubleRedAve
 tile_color 0xff0001
 selected true
 xpos 1091
 ypos 143
 addUserKnob {20 User}
 addUserKnob {7 LimitPercentage l "fine tune" R 0.5 1.5}
 LimitPercentage 1
}
push $N2eb50ba0
Expression {
 expr1 g>(2*b+r)/3*LimitPercentage?(2*b+r)/3*LimitPercentage:g
 expr3 g-(r+b)*LimitPercentage/2
 name DoubleBlueAve
 tile_color 0xff0001
 selected true
 xpos 979
 ypos 143
 addUserKnob {20 User}
 addUserKnob {7 LimitPercentage l "fine tune" R 0.5 1.5}
 LimitPercentage 1
}
push $N2eb50ba0
Expression {
 expr1 g>(b+r)/2*LimitPercentage?(b+r)/2*LimitPercentage:g
 expr3 g-(r+b)*LimitPercentage/2
 name AverageGreen
 tile_color 0xff0001
 selected true
 xpos 869
 ypos 143
 addUserKnob {20 User}
 addUserKnob {7 LimitPercentage l "fine tune" R 0.5 1.5}
 LimitPercentage 1
}
push $N2eb50ba0
Expression {
 expr1 g>b*LimitPercentage?b*LimitPercentage:g
 expr3 g-b*LimitPercentage
 name BlueLimitsGreen
 tile_color 0xff0001
 selected true
 xpos 759
 ypos 143
 addUserKnob {20 User}
 addUserKnob {7 LimitPercentage l "fine tune" R 0.5 1.5}
 LimitPercentage 1
}
push $N2eb50ba0
Expression {
 expr1 g>r*LimitPercentage?r*LimitPercentage:g
 expr3 g-r*LimitPercentage
 name RedLimitsGreen
 tile_color 0xff0001
 selected true
 xpos 650
 ypos 143
 addUserKnob {20 User}
 addUserKnob {7 LimitPercentage l "fine tune" R 0.5 1.5}
 LimitPercentage 1
}

05. Transform

Tools you can use to transform and manipulate your image.

06. 3D and Deep

Some useful tools for 3D space and Deep Compositing.

NORMAL PASS - RELIGHT
Use the Normal Pass to create a new light in the alpha channel.

Show/Hide node script

set cut_paste_input [stack 0]
version 10.5 v2
push $cut_paste_input
add_layer {normal normal.red normal.green normal.blue normal.alpha}
Shuffle {
 in normal
 name Shuffle2
 label "\[value in]"
 selected true
 xpos 1370
 ypos 205
}
Expression {
 expr3 max((r*norm.r)+(g*norm.g)+(b*norm.b),0)
 name Expression1
 label RELIGHT
 selected true
 xpos 1370
 ypos 259
 addUserKnob {20 User}
 addUserKnob {7 round l left/right R -100 100}
 round 1
 addUserKnob {7 around l up/down R -100 100}
 around 1
 addUserKnob {26 ""}
 addUserKnob {7 rad}
 rad {{cos(radians(around))}}
 addUserKnob {7 lx}
 lx {{rad*cos(radians(round))}}
 addUserKnob {7 ly}
 ly {{sin(radians(around))}}
 addUserKnob {7 lz}
 lz {{rad*sin(radians(round))}}
 addUserKnob {18 norm}
 norm {{lx/sqrt(pow2(lx)+pow2(ly)+pow2(lz))} {ly/sqrt(pow2(lx)+pow2(ly)+pow2(lz))} {lz/sqrt(pow2(lx)+pow2(ly)+pow2(lz))}}
 addUserKnob {6 norm_panelDropped l "panel dropped state" -STARTLINE +HIDDEN}
}

COORDINATES
Create a map of coordinates.

C4x4
Matrix 4x4 to project the object in the 3D space and apply a distortion.

UV Map

Show/Hide node script

set cut_paste_input [stack 0]
version 10.5 v2
push $cut_paste_input
Group {
 name UV_Map
 help "Create an uvmap from the input format or the selected format that can be used for example for baking transformations and applying them through a STmap node.\nUse the overscan to create values outside of the viewing window and the 0-1 range."
 note_font "Bitstream Vera Sans"
 selected true
 xpos 1062
 ypos 295
 mapsize {0.15 0.15}
 addUserKnob {20 tab l "UV Map"}
 addUserKnob {41 format T Constant1.format}
 addUserKnob {41 scale l overscan T Reformat1.scale}
 addUserKnob {6 alpha l "alpha 1" +STARTLINE}
}
 Input {
  inputs 0
  name Input1
  xpos 620
  ypos -370
 }
 Shuffle {
  red black
  green black
  blue black
  alpha black
  name Shuffle1
  xpos 620
  ypos -309
 }
 Constant {
  inputs 0
  name Constant1
  xpos 479
  ypos -214
 }
 Switch {
  inputs 2
  which {{"\[exists parent.input0]"}}
  name Switch1
  xpos 620
  ypos -191
 }
 Reformat {
  type scale
  black_outside true
  pbb true
  name Reformat1
  xpos 620
  ypos -71
 }
 Reformat {
  type scale
  scale {{1/Reformat1.scale} {1/Reformat1.scale}}
  resize none
  black_outside true
  pbb true
  name Reformat2
  xpos 620
  ypos -37
 }
 Shuffle {
  alpha white
  name Shuffle13
  tile_color 0xffffff00
  label "\[value in]"
  xpos 620
  ypos 12
  disable {{!parent.alpha}}
 }
 Expression {
  expr0 (x+0.5)/width
  expr1 (y+0.5)/height
  name Expression2
  xpos 620
  ypos 75
 }
 Output {
  name Output1
  xpos 620
  ypos 127
 }
end_group

Deep to Depth
Convert the Deep into Depth

Show/Hide node script

set cut_paste_input [stack 0]
version 10.5 v2
push $cut_paste_input
DeepToImage {
 name DeepToImage1
 selected true
 xpos 785
 ypos 230
}
AddChannels {
 channels depth
 name AddChannels1
 selected true
 xpos 785
 ypos 277
}
Expression {
 channel3 depth
 expr3 "deep.r == 0 ? inf : deep.r"
 name DeepToDepth
 selected true
 xpos 785
 ypos 336
}

Deep Thickness
Smooth the front and back layers. Really useful to smooth elements inside deep smoke.

Show/Hide node script

set cut_paste_input [stack 0]
version 10.5 v2
push $cut_paste_input
DeepExpression {
 temp_name3 t
 temp_expr3 "\[value tickness]/2"
 chans1 deep
 deep.front deep.front-t
 deep.back deep.back+t
 name DeepThickness
 selected true
 xpos 918
 ypos 244
 addUserKnob {20 Thickness}
 addUserKnob {7 thickness R 0 100}
}

Expression Node Collection

My personal collection of tools with the Expression Node

Expression Node

HOW TO INSTALL IT?

Useful Links

Overview

Show/Hide node script

Show/Hide node script

Show/Hide node script

Show/Hide node script

Show/Hide node script

Show/Hide node script

Show/Hide node script

Show/Hide node script

Show/Hide node script

Show/Hide node script

Show/Hide node script

Show/Hide node script

Questions about this tutorial?