The Original Concept: A Moving Artery

While browsing through my collection of FLA files, I stumbled on an experiment called vein-1 that was created by a fellow Flash developer, Mike Johnson. I was inspired to recreate it in ActionScript 2 and spice up the implementation. The result was a perpetually moving artery with branches of veins and capillaries branching from it at random points (see Figure 1).

Figure 1: The original experiment—a perpetually moving artery with branching veins

Briefly, the VeinManager class instantiates a single instance of a Vein class, which becomes the artery. In each frame, the Vein class randomly alters its angle of movement, and draws a line segment with a random length along that angle. It also randomly instantiates new Vein classes with a lower thickness, and the same initial angle and location as the artery. These child veins then carry out the same functions (drawing line segments and creating children of their own) for a random number of frames.

This experiment obviously generated a lot of line segments, and would quickly overwhelm the ability of Flash Player to composite the vectors. To reduce the impact of vector compositing, the Vein instances in the original experiment fade and remove themselves from the Stage after a few seconds. In Flash Player 8, I was able to make the veins persistent by using a custom bitmap caching routine.