Eyeon:Manual/Tool Reference/Misc/Custom Tool

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Custom [Cu]


The Custom tool is quite likely the most complex, and the most powerful, tool in Fusion. Any user moderately experienced with scripting, or C++ programming, should find the structure and terminology used by the Custom tool to be familiar.

The Custom tool is used to create custom expressions and filters to modify an image. In addition to providing three image inputs, the Custom tool will allow for the connection of up to eight numeric inputs and as many as four XY position values from other controls and parameters in the flow.

Per-pixel calculations can be performed on the Red, Green, Blue, Alpha, Z, Coverage, UV texture coords, XYZ Normals, Background RGBA and XY Vector channels of the images.


Custom Controls Tab

Point In 1-4, X And Y

These four controls are 2D X and Y center controls that are available to expressions entered in the Setup, Intermediate and Channels tabs as variables p1x, p1y, ...., p4x, p4y. They are normal positional controls and can be animated or connected to modifiers as any other tool might.

Number In 1-8

The values of these controls are available to expressions entered in the Setup, Intermediate and Channels tabs as variables n1, n2, n3, ..., n8. They are normal slider controls, and can be animated or connected to modifiers exactly as any other tool might.

These controls can be renamed using the options in the Config tab to make their meanings more apparent, but expressions will still see the values as n1, n2, ..., n8.

Custom Setup Tab

Setup 1-4

Up to four separate expressions can be calculated in the Setup tab of the Custom tool. The Setup expressions are evaluated once per frame, before any other calculations are performed. The results are then made available to the other expressions in the Custom tool as variables s1, s2, s3 and s4.

Note: Because these expressions are evaluated once per frame only and not for each pixel, it makes no sense to use per-pixel variables like x & y or channel variables like r1,g1,b1 etc. Allowable values include constants, variables like n1..n8, time, w & h etc, and functions like sin() or getr1d().

Custom Inter Tab

Intermediate 1-4

An additional four expressions can be calculated in the Inter tab. The Inter expressions are evaluated once per pixel, after the Setup expressions are evaluated but before the Channel expressions are evaluated. Results are available as variables i1, i2, i3 and i4.

Custom Config Tab

The Config tab allows customization of the controls in the Controls tab, simplifying adjustments to the tool. Sliders and point controls can be renamed and hidden. If different types of controls are needed, the UserControls script may be used to add them. The existing sliders can be linked to the new control with expressions, as in this example.

Random Seed

Use this to set the seed for the rand() and rands() functions. Click the Randomize button to set the seed to a random value. This control may be needed if multiple Custom tools are required with different random results for each.

Number Controls

There are eight sets of Number controls, corresponding to the eight Number In sliders in the Controls tab. Untick the Show Number checkbox to hide the corresponding Number In slider, or edit the Name for Number text field to change its name.

Point Controls

There are four sets of Point controls, corresponding to the four Point In controls in the Controls tab. Untick the Show Point checkbox to hide the corresponding Point In control and its crosshair in the Display view. Similarly, edit the Name for Point text field to change the control's name.

Channels Tab

RGBA, Z, UV Expressions And XYZ Normal Expressions

The Channel tab is used to set up one expression per each available channel of the image. Each expression is evaluated once per pixel, and the result is used to create the value for that pixel in the output of the image.

Color Channel expressions (RGBA) should return Floating Point values between 0.0 and 1.0, and all other expression values must produce values between -1.0 and 1.0. The Channel expressions may use the results from both the Setup expressions (as variables s1-s4) and Inter expressions (as variables i1-i4).

Custom Tool Syntax

, ,
Value Variables
n1..n8Numeric Inputs
p1x..p4xPosition Values (X-axis)
p1y..p4yPosition Values (Y-axis)
s1..s4Setup Expression Results
i1..i4Inter Expression Results
timeCurrent Frame
xHorizontal co-ordinate of the current pixel, between 0.0 and 1.0
yVertical co-ordinate of the current pixel, between 0.0 and 1.0
w (or w1..w3)Width of Image (for image1..image3)
h (or h1..h3)Height of Image (for image1..image3)
ax (or ax1..ax3)Image Aspect X (for image1..image3)
ay (or ay1..ay3)Image Aspect Y (for image1..image3)


Use w & h and ax & ay without a following number to get the dimensions and aspect of the primary image.
Channel (Pixel) Variables
c1..c3Current Channel (for image1..image3)
r1..r3Red (for image1..image3)
g1..g3Green (for image1..image3)
b1..b3Blue (for image1..image3)
a1..a3Alpha (for image1..image3)
z1..z3Z-Buffer (for image1..image3)
cv1..cv3Coverage (for image1..image3)
u1..u3U Coordinate (for image1..image3)
v1..u3V Coordinate (for image1..image3)
nx1..nx3X Normal (for image1..image3)
ny1..ny3Y Normal (for image1..image3)
nz1..nz3Z Normal (for image1..image3)
bgr1..bgr3Background Red (for image1..image3)
bgg1..bgg3Background Green (for image1..image3)
bgb1..bgb3Background Blue (for image1..image3)
bga1..bga3Background Alpha (for image1..image3)
vx1..vx3X Vector (for image1..image3)
vy1..vy3Y Vector (for image1..image3)


Use c1, c2, c3 to refer to the value of a pixel in the current channel. This makes copy/pasting expressions easier. For example, if c1/2 is typed as the red expression, the result would be half the value of the red pixel from image 1, but if the expression is copied to the blue channel, now it would have the value of the pixel from the blue channel.
To refer to the red value of the current pixel in input one, type r1. For the image in input 2, it would be r2.
get[ch][#]b(x, y)Read pixel at x,y, or 0 if out of bounds.
e.g. getr1b(0,0)
get[ch][#]d(x, y)Read pixel at x,y or edge pixel if out of bounds.
e.g. getr1d(0,0)
get[ch][#]w(x, y)Read pixel at x,y or wrap if out of bounds
e.g. getr1w(0,0)


There are a variety of methods used to refer to pixels from other locations than the current one in an image.
In the above description [ch] is a letter representing the channel to access, and [#] is a number representing the input image. So to get the red component of the current pixel (equivalent to 'r'), you would use getr1b(x,y). To get the alpha component of the pixel at the center of image 2 you would use geta2b(0.5, 0.5).
output the red value of the pixel at position x, y, if there were a valid pixel present. It would output 0.0, if the position were beyond the boundaries of the image (all channels).
output the red value of the pixel at position x, y. If the position specified were outside of the boundaries of the image, the result would be from the outer edge of the image (RGBA only).
output the red value of the pixel at position x, y. If the position specified were outside of the boundaries of the image, the x and y co-ordinates would wrap around to the other side of the image and continue from there (RGBA only).
To access other channel values with these functions, substitute the r in the above examples with the correct channel variable. (r, g, b, a and, for the getr1b() functions only, z, etc...) as shown above. Substitute the 1 with either 2 or 3 in the above examples to access the images from the other image inputs.
Mathematical Expressions
piThe value of pi
eThe value of e
log(x)The base-10 log of x
ln(x)The natural (base-e) log of x
sin(x)The sine of x (x is degrees)
cos(x)The cosine of x (x is degrees)
tan(x)The tangent of x (x is degrees)
asin(x)The arcsine of x, in degrees
acos(x)The arccosine of x, in degrees
atan(x)The arctangent of x, in degrees
atan2(x,y)The arctangent of x,y, in degrees
abs(x)The absolute (positive) value of x
int(x)The integer (whole) value of x
frac(x)The fractional value of x
sqrt(x)The Square Root of x
rand(x,y)A random value between x and y
rands(x,y,s)A random value between x and y, based on seed s
min(x,y)The minimum (lowest) of x and y
max(x,y)The maximum (highest) of x and y
dist(x1,y1,x2,y2)The distance between point x1,y2 and x2,y2
dist3d(x1,y1,z1,x2,y2,z2)The distance between 3D points x1,y2,z1 and x2,y2,z2
noise(x)A smoothly varying Perlin noise value based on x
noise2(x, y)A smoothly varying Perlin noise value based on x and y
noise3(x, y, z)A smoothly varying Perlin noise value based on x, y and z
if(c, x, y)returns x if c <> 0, otherwise y
Mathematical Operators
!x1.0 if x = 0, otherwise 0.0
-x(0.0 - x)
+x(0.0 + x) i.e. effectively does nothing
x^yx raised to the power of y
x*yx multiplied by y
x/yx divided by y
x%yx modulo y, i.e. remainder of (x divided by y)
x+yx plus y
x-yx minus y
x<y1.0 if x is less than y, otherwise 0.0
x>y1.0 if x is greater than y, otherwise 0.0
x<=y1.0 if x is less than or equal to y, otherwise 0.0
x>=y1.0 if x is greater than or equal to y, otherwise 0.0
x=y1.0 if x is exactly equal to y, otherwise 0.0
x==y1.0 if x is exactly equal to y, otherwise 0.0, identical to above
x<>y1.0 if x is not equal to y, otherwise 0.0
x!=y1.0 if x is not equal to y, otherwise 0.0, i.e. identical to above
x & y1.0 if both x and y are not 0.0, otherwise 0.0
x && y1.0 if both x and y are not 0.0, otherwise 0.0, i.e. identical to above
x | y1.0 if either x or y (or both) are not 0.0, otherwise 0.0
x || y1.0 if either x or y (or both) are not 0.0, otherwise 0.0


The following examples are intended to help you understand the various components of the Custom tool.


To rotate an image, we need the standard equations for 2D rotation:

x' = x * cos(theta) - y * sin(theta)
y' = x * sin(theta) + y * cos(theta)

Using the n1 slider for the angle theta, and a sample function, we get (for the red channel)

getr1b(x * cos(n1) - y * sin(n1), x * sin(n1) + y * cos(n1))

This will calculate the current pixel's (x,y) position rotated around the origin at (0,0) (the bottom-left corner), and then fetch the red component from the source pixel at this rotated position. For centred rotation, we need to subtract 0.5 from our x and y coordinates before we rotate them, and add 0.5 back to them afterwards:

getr1b((x-.5) * cos(n1) - (y-.5) * sin(n1) + .5, (x-.5) * sin(n1) + (y-.5) * cos(n1) + .5)

Which brings us to the next lesson: Setup and Intermediate expressions. These are useful for speeding things up by minimising the work that gets done in the channel expressions. The Setup expressions are executed only once, and their results don't change for any pixel, so you can use these for s1 and s2 respectively:


Intermediate expressions are executed once for each pixel, so you can use these for i1 and i2:

(x-.5) * s1 - (y-.5) * s2 + .5
(x-.5) * s2 + (y-.5) * s1 + .5

These are the x & y parameters for the getr1b() function, from above, but with the Setup results, s1 and s2, substituted so that the trig functions are executed only once per frame, not every pixel. Now you can use these intermediate results in your channel expressions:

getr1b(i1, i2)
getg1b(i1, i2)
getb1b(i1, i2)
geta1b(i1, i2)

With the Intermediate expressions substituted in, we only have to do all the adds, subtracts and multiplies once per pixel, instead of four times per pixel. As a rule of thumb, if it doesn't change, do it only once.

This is a simple rotation that doesn't take into account image aspect at all. It is left as an exercise to the reader to include this (sorry). Another improvement could be to allow rotation around different points than the center.


Our second example duplicates the functionality of a 3x3 Custom Filter tool set to averages the current pixel together with the eight pixels surrounding it. To duplicate it with a Custom tool, add a Custom tool to the Flow, and enter the following expressions into the Setup tab.

(Leave the tool disconnected to prevent it from updating until we are ready.)


These two expressions will be evaluated at the beginning of each frame. S1 divides 1.0 by the current width of the frame, and S2 divides 1.0 by the height. This provides a Floating Point value between 0.0 and 1.0 that represents the distance from the current pixel to the next pixel along each axis.

Now enter the following expression into the first text control of the Channel tab (r)

 (getr1w(x-s1, y-s2) + getr1w(x, y-s2) + getr1w(x+s1, y-s2) + 
  getr1w(x+s1, y) + getr1w(x-s1, y) + r1 + 
  getr1w(x-s1, y+s2) + getr1w(x, y+s2) + getr1w(x+s1, y+s2)) / 9

This expression adds the nine pixels above the current pixel together by calling the getr1w() function nine times and providing it with values relative to the current position. Note that we referred to the pixels by using x+s1, y+s2 rather than using x+1, y+1.

Fusion refers to pixels as Floating Point values between 0.0 and 1.0, which is why we created the expressions we used in the Setup tab. If we had used x+1, y+1 instead, the expression would have sampled the exact same pixel over and over again. (The function we used wraps the pixel position around the image if the offset values are out of range.)

That took care of the red channel, now use the following expressions for the green, blue and alpha channels.

 (getg1w(x-s1, y-s2) + getg1w(x, y-s2) + getg1w(x+s1, y-s2) + 
  getg1w(x+s1, y) + getg1w(x-s1, y) + g1 + 
  getg1w(x-s1, y+s2) + getg1w(x, y+s2) + getg1w(x+s1, y+s2)) / 9

 (getb1w(x-s1, y-s2) + getb1w(x, y-s2) + getb1w(x+s1, y-s2) + 
  getb1w(x+s1, y) + getb1w(x-s1, y) + b1 + 
  getb1w(x-s1, y+s2) + getb1w(x, y+s2) + getb1w(x+s1, y+s2)) / 9
 (geta1w(x-s1, y-s2) + geta1w(x, y-s2) + geta1w(x+s1, y-s2) + 
  geta1w(x+s1, y) + geta1w(x-s1, y) + a1 + geta1w(x-s1, y+s2) + 
  geta1w(x, y+s2) + geta1w(x+s1, y+s2)) / 9

It is time to view the results. Add a Background tool set to solid color and change the color to a pure red. Add a hard edged rectangular Effects Mask and connect it to the expression just created.

For comparison, add a Custom Filter tool and duplicate the settings from the image above. Connect a pipe to this tool from the background to the tool and view the results. Alternate between viewing the Custom tool and the Custom Filter while zoomed in close to the top corners of the Effects Mask.

Of course, the Custom Filter tool renders a lot faster than the Custom tool we created, but the flexibility of the Custom tool is its primary advantage. For example, you could use an image connected to input 2 to control the median applied to input one by changing all instances of getr1w, getg1w, and getb1w in the expression to getr2w, getg2w, and getb2w, but leaving the r1, g1, and b1s as they are.

This is just one example, the possibilities of the Custom tool are limitless.

The contents of this page are copyright by eyeon Software.

Tips for Custom Tool (edit)

Adding CustomTool to comp through Python Script:

# Python Script
# The script name of CustomTool is Custom
customTool = comp.AddTool("Custom")
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