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Plasma effect

Demoscene

Concepts

•

Demo

• Intro

• Demoparty

• Effects

• Demogroup

• Compo

• Music disk

• Diskmag

• Module file

•  Tracker

Alternative demo platforms

• Amiga

• Apple IIGS

• Atari ST

• Commodore 64

• Vic-20

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•  Text mode

• ZX Spectrum

Current parties

• Alternative Party

• Assembly

• Buenzli 

• Evoke

•  The Gathering

• Revision

• Sundown

• X

Past parties

• Breakpoint

•  The Party

Websites

•

Scene.org

• Mod Archive

Software

• ProTracker

• Scream Tracker

• Fast Tracker

• Impulse Tracker

• ModPlug

• Renoise

•  Tracker musicians

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• Demosceners

• v

• t

• e

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

A still screenshot of a typical plasma effect.

Animated color cycling feature as in Fractint

Plasma was probably invented by demo coders for use in their demos wherethe effect was heavily used, especially in the early 1990s. The effect wasparticularly common on the Commodore Amiga where it could beimplemented very efficiently by using the features of the proprietary displayhardware. Plasma can also be implemented easily in software rendering byusing sinus tables and pseudocolor palettes, and it has also been the firsttrue 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 thesoftware, can provide a result which resembles a typical plasma effect usedin demos. The technical basis, however, is completely different, and a colorcycling plasma is somewhat less dynamic than a demo plasma.

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Synopsis

A plasma effect rendered in ANSI 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 theoretical basis for theeffect. In order to achieve a sufficiently fast and good-looking real-timeimplementation (especially on the limited hardware available at the time thiseffect was at the height of its popularity in the 1990s), one would often do"non-correct" approximations to this algorithm. This, however, can often bedone without noticeable visual differences.

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

Let be a multi-frequency noise function of two 2 variables (e.g., a

perlin noise function). Let each color component at the pixel be a

linear function of the expression .