Plasma effect

The plasma effect is a computer-based visual effect animated in real time. It uses cycles of changing colours warped in various ways to give an illusion of liquid, organic movement.

A still screenshot of a typical plasma effect.

Plasma was probably invented by demo coders for use in their demos where the effect was heavily used, especially in the early 1990s. The effect was particularly common on the Commodore Amiga where it could be implemented very efficiently by using the features of the proprietary display hardware. Plasma can also be implemented easily in software rendering by using sinus tables and pseudocolor palettes, and it has also been the first true demo effect for many beginning PC democoders.

The fractal software Fractint also incorporates an algorithm known as "plasma", which, when combined with the color cycling feature of the software, can provide a result which resembles a typical plasma effect used in demos. The technical basis, however, is completely different, and a color cycling plasma is somewhat less dynamic than a demo plasma.

Synopsis

A plasma effect rendered in ASCII art by the AAlib library.

As there are many "hacked" approaches for implementing a plasma effect, this outline of an algorithm will just describe the theroetical basis for the effect. In order to achieve a sufficiently fast and good looking real time implementation (especially on the limited hardware available at the time this effect was at the height of its popularity in the 1990s), one would often do "non-correct" approximations to this algorithm. This, however, can often be done without noticeable visual differences.

This algorithm is given in two dimensions, but could easily be adopted to any number of dimensions for any number of color channels.

Let $f(x,y)$ be a multi-frequency noise function of two 2 variables (e.g., a perlin noise function). Let each color component $c$ at the pixel $(x,y)$ be a linear function of the expression $sin(f(x,y)*freq_{c})$.

See also

Diamond-square algorithm is a fractal that the plasma effect can be applied to with nice results.

External links

• Java applet demonstrating plasma effect

• Plasma Pong, a variation of Pong that utilizes real-time fluid dynamics to drive the game environment