Inside and outside

To calculate a pixel in a fractal, Ultra Fractal iterates the fractal formula selected in the Formula tab 

of the 

Layer Properties

 tool window. The formula is executed multiple times, each time using the 

result from the previous calculation as input.

The formula is iterated until the maximum iteration count (set in the Formula tab) is reached, or until 

the bail out condition (specified by the fractal formula) is met. If the bail out condition is met, the 

pixel is colored as an outside pixel. Otherwise, it is colored as an inside pixel.

Most classic fractal types, such as the 

Mandelbrot set

, are actually a set of points. A pixel can either 

be inside or outside the set. If a pixel is inside, it belongs to the Mandelbrot set, for example. 

In this image of the Mandelbrot set, the inside area is black. The 

outside area is colored according to the number of iterations 

required to meet the bail out condition.

By iterating the fractal formula, Ultra Fractal decides whether a pixel is inside or outside the set. The 

pixels that are inside are colored according to the settings in the Inside tab of the Layer Properties 

tool window. The pixels that are outside are colored according to the settings in the Outside tab.

The Inside and Outside tabs are identical and provide the same options and settings. Since the 

outside area is usually the most interesting area, you will probably use the Outside tab more often.

Notes

G     

Some coloring algorithms can only be used in the Inside tab, or only in the Outside tab.

G     

Some fractal formulas can change the meaning of inside and outside areas. For example, 

they can be intended to work together with a special outside coloring algorithm, and ignore 

the settings for inside areas. This is usually noted in the comments at the top of the formula.

Next: 

Working with coloring algorithms

See Also

Maximum iterations

Coloring algorithms

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