Writing coloring algorithms

Coloring algorithms are put in coloring algorithm files with the .ucl extension. They can have the 

following sections, in this order:

G     

global

G     

init

G     

loop

G     

final

G     

default

If a coloring algorithm does not start with a label, it is assumed to start with the final section (in 

that case, the init and loop sections are not allowed).

The optional setting within parentheses after the entry identifier specifies whether the coloring 

algorithm can be used for inside coloring, outside coloring, or both. The possible values are:

INSIDE

The coloring algorithm is only intended for coloring the inside of a fractal.

OUTSIDE

The coloring algorithm is only intended for coloring the outside of a fractal.

If the setting is omitted, or has another value, the coloring algorithm is supposed to be useful for 

both inside and outside coloring. See also 

Inside and outside

.

The global section is executed only once per image and can be used to fill look up tables and 

initialize read only variables. See 

Global sections

.

The init section is executed only once per pixel, and is useful for initializing variables.

The loop section is executed once per iteration, right after the loop section of the fractal formula 

has been executed. It can read the current value of 

#z

 and perform some calculations on it.

The final section is executed afterwards to determine the actual index into the gradient (this index is 

further transformed by the various settings on the Inside or Outside tabs). The index is a float value 

and should be written to the predefined symbol 

#index

. If the settings on the Inside or Outside tab 

are set to their default values (Density = 1, Transfer = Normal and Offset = 0), the entire gradient 

range corresponds to the range 0..1 of the index value.

To create a 

direct coloring algorithm

, use the predefined symbol 

#color

 instead of #index.

It is also possible to set the predefined symbol 

#solid

 to true: this gives the pixel the 

solid color

 set 

in the Inside or Outside tab of the 

Layer Properties

 tool window.

The default section can contain the following settings:

G     

helpfile

G     

helptopic

G     

precision

G     

render

G     

title

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