fracexpl - JavaScript Fractal Explorer

This repository is the project home for fracexpl.js, a fractal explorer designed to be embedded in a web page. The design and user interface is taken from the Java applet developed by Peter Van Roy and others at RPI to accompany the "African Fractals" lessons by Ron Eglash. See Ron Eglash's web page (http://homepages.rpi.edu/~eglash/eglash.htm) and the Culturally Situated Design Tools website (https://csdt.rpi.edu/) for more information and full credits for the original applet.

For a live example (using src/example.html) see https://span.uncg.edu/fractals/example.html.

Usage

To include the fractal explorer in a web page, you must do two things:

1. Include the JavaScript source in the head section of your web page, and include a copy of Bootstrap CSS (required for button styling and a few other visual elements). You must have the button images (button1.png through button6.png) in the same directory as the JavaScript source.

2. Include an empty div with class=fractaltool, which can take some optional data properties:

• data-width: The width of the fractal explorer canvas in pixels. The minimum width is 640, and the default is 800 if this is not specified.

• data-height: The height of the fractal explorer canvas in pixels. The minimum height is 320, and the default is 600 if this is not specified.

• data-seed: The name of a seed to load into the fractal explorer when it is initialized. This must be a built-in fractal name, from the list given below.

• data-seedlist: A comma-separated list of fractals to include in the dropdown list of standard fractals that can be loaded in edit mode.

• data-mode: Set to "draw" to start the fractal explorer in drawing mode (by default it starts in edit mode).

• data-levels: Initial number of levels of recursion for drawing mode (default is 1).

The JavaScript will will insert the fractal explorer into the div once the page has loaded. See src/example.html for an example.

Built-in Fractals

The following fractal seeds are hard-coded into the fracexpl.js file, and can be used by including the name as data-seed or in the list of names in data-seedlist. These seeds were converted from the original Java applet seeds, extracted from data files supplied by Ron Eglash. Most are used in the "African Fractals" lessons -- see those lessons for more information.

• 3crosses
• baila
• blanket
• bullhorn
• cantorpaper
• carpet
• chaetophora
• cnegative
• cpositive
• davincitree2
• davincitree3
• davincitree4
• dendrite
• ethiopian2
• ethiopian
• fern
• fractalsprials
• ghanahorns
• goldenrec
• kitwe
• koch
• kochsmall
• logone
• lungs
• mokoulek
• nankani
• negative
• neuron
• positive
• queenanne
• riverbasin
• sierpinski
• sprout
• turbulence
• villi
• sharkfin

Room for Improvement

The code is fully functional for use in the original application, the "African Fractals" lessons from Ron Eglash. The JavaScript code is organized around a general multi-modal editor, with each of the two basic modes (draw mode and edit mode) defined in a JavaScript class. Below are some directions for future improvements or extensions:

Extension for variable-width drawing lines

The original Java applet had an option for the drawing linewidth to decrease with each level of recursion. This property is preserved in the standard seed definitions, stored as thicknessType, but this is not actually used in drawing and there is no way to enable/disable this in edit mode. Adding support would involve modifying the drawing function (which should be easy) and adding the control in edit mode.

General code cleanup

There are two main places where the code could benefit from better design. First, classes were defined for each mode (edit mode and draw mode), and the actual seed definition data is somewhat arbitrarily stored in the draw mode object. Having a separate FractalSeed class that is separate from either mode would be better. Second, generated DOM elements are given ids that are not necessarily unique if there are multiple fractal explorer instances on a single page. This doesn't seem to cause a problem, since these elements aren't reference by id, but nonetheless id attributes should be distinct on principle.

Better double-click handling

On a double-click, JavaScript delivers both Click and DblClick events. While this is inherrent in JavaScript, and the current code appears to handle this OK, it seems like there should be a better way to distinguish between single clicks and double clicks.

License

fracexpl.js is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License (GNU GPL) as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. The code is distributed WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU GPL for more details.

As additional permission under GNU GPL version 3 section 7, you may distribute non-source (e.g., minimized or compacted) forms of that code without the copy of the GNU GPL normally required by section 4, provided you include this license notice and a URL through which recipients can access the Corresponding Source.