Sterling Program Instructions

by Tad Boniecki at
Updated in January 2017

Sterling2 is based on Sterling, a fractal-generating program written in 1999 by Stephen C. Ferguson. Apart from the name, the program looks just like the original Sterling. Note that I have not changed the formula descriptions - these are incorrect in Sterling2. The only part that has changed are the 50 formulae that one can choose from.

These instructions apply equally to Sterling and to Sterling2, as the two programs are identical except for having different formulas.

The first thing I do when I fire up Sterling (or Sterling2) is to maximise the program window. Then I either select a formula and paint a fractal or, more often, I open an existing fractal image and work on that. Both procedures are described below.

Starting from scratch
Choose a formula from Form I, Form II or Form III. Then select a rendering from Rend I or Rend II. Alternately, you can skip these two steps and begin working on the fractal that the program presents to you immediately.

Working on an existing fractal image
Click on File and then on Load From Parameter File. Select a file with extension ".loo". Note that the File -> Open command is not very useful because it only shows you the image, ie it does not allow you to modify it.

Changing the size of the fractal image
When Sterling starts it paints a tiny image. This has the advantage of rendering quickly, but it is hard to work with. So usually, one of the first things to do is to change the image size. I use my screen resolution of 1280 x 1024, but you may want to use a smaller size to save time rendering. To change the render size, click on the centre yellow icon that shows three squares. Then specify the width and height in pixels and click Apply. Close the XYSize window. The fractal will now render in the size you specified. It's a good idea to maximise the image window as well.

This is the most frequent operation involved in fractal generation. There are two ways to zoom into an existing image in Sterling. By default, a single left-click inside the image will enlarge the area around the point where you click. This is quick and simple. However, this method does not suit me at all. I prefer to draw a zoom window with the mouse, so that I can specify exactly which area I want to enlarge to full-screen. To do this, right click on the image and select "Rectangle Mode" and de-select "Zoom In/ Out mode". Then left click inside the image and draw the zoom window with the mouse. Finally, double click inside the zoom window. Unfortunately, each time you open a parameter file Sterling reverts to Zoom In/Out mode.

If you have zoomed in too far and want to zoom back out a bit, then draw a window larger than the current render size (you may have to decrease this first) and then double click inside that.

Saving an image
Once you have an image you like and want to keep, click on File -> Save As. The program will by default save a bmp image or you can specify jpg. I recommend bmp as this is lossless. Whatever name and format you specify for the image, Sterling will save another file of the same name with extension loo. This is the parameter file, which allows you to modify or redraw the fractal at a later time. You may want to save an image that you want to develop further in the future. If you make a lot of fractals then you may want to use a systematic naming method.

Colour controls
You may well create an interesting shape but with yucky colours. There are three ways to change colours in Sterling.
A) Click on the red, blue and green crayon icon and move one or more of the six sliders. This method gives quite a lot of control. If you like bright colours then make the saturation 100%.
B) Select a different colour from Color I or Color II. I recommend #8, 10, 11 and 12.
C) Click on rgb and select a different combination from the six possibilities.
Whichever method you use, it's a good idea to make the fractal small until you get colours you like. I recommend 600 x 400, as this size or smaller will render immediately. Otherwise, it may take a long time to find a pleasing version. You can also change the colours of a fractal using any graphics program, eg Photoshop. This is called "post-processing".

These change the way that a given formula is drawn. I recommend trying #26. Many of the images on the display pages were made using this render. I also recommend numbers 8 and 14-17.

The Image menu
This has three useful functions. If you tick Julia Mode and click on Draw then the program draws the Julia version of the fractal, which will be quite different. Likewise, ticking Inside Out draws a quite different version of the same fractal. Reset Co-ordinates is useful if you want to get back to the initial view of the fractal, ie zoom back out.

Julia mode
There are myriad Julia versions of every Sterling2 fractal. You can exercise fine control over the image by clicking on Fractal Parameters (the icon under Form II). By changing the Julia x or Julia y parmeters you will alter the image.

If the program gives an error when you ask it to render a Julia fractal inside out, there is a work-around. Switch off Julia mode, render the fractal as a small image then zoom into it and specify Julia mode for the zoom. This will also give an error, but if you zoom in again then the program will render the image inside out in Julia mode.

These can do something interesting.

Improving the image
Have a try at anti-aliasing. Sterling images are particularly good candidates for anti-aliasing. Render the image at 16 times the size (eg 5120x4096 if your intended resolution is 1280x1024). Then do Image->Anti-alias 4:1. You can save this version. To continue working on the image you will need to redraw it, so make the resolution smaller and hit Apply.

The Lyapunov options
The menu options Lyapunov, LyapunovDerivative and LyapunovMapping only apply to renders 30 to 32. Once you use these renders you have to reload a parameter file to switch off Lyapunov.

General Pointers
I suggest zooming into the most interesting or complicated part of the fractal. Perseverence is not always rewarded - sometimes I spend an hour and fail to make even one image that I like. At other times I hit a seam of excellent material that produces one good image after another. Be flexible and keep trying. Once you have made a few dozen good images you can use these as a base from which to make further images, by zooming in or changing parameters like colour, render, and transform. The easiest way to create a good new fractal is to modify an existing one.