Demo effect
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Demo effect is computer-based
real-time Real-time or real time describes various operations in computing or other processes that must guarantee response times within a specified time (deadline), usually a relatively short time. A real-time process is generally one that happens in defined ...
visual effects Visual effects (sometimes abbreviated VFX) is the process by which imagery is created or manipulated outside the context of a live-action shot in filmmaking and video production. The integration of live-action footage and other live-action foota ...
found in
demos Demos may refer to: Computing * DEMOS, a Soviet Unix-like operating system * DEMOS (ISP), the first internet service provider in the USSR * Demos Commander, an Orthodox File Manager for Unix-like systems * plural for Demo (computer programming) ...
created by the
demoscene The demoscene is an international computer art subculture focused on producing demos: self-contained, sometimes extremely small, computer programs that produce audiovisual presentations. The purpose of a demo is to show off programming, visual ...
. The main purpose of demo effects in demos is to show off the skills of the programmer. Because of this, demo coders have often attempted to create new effects whose technical basis cannot be easily figured out by fellow programmers. Sometimes, particularly in the case of severely limited platforms such as the
Commodore 64 The Commodore 64, also known as the C64, is an 8-bit home computer introduced in January 1982 by Commodore International (first shown at the Consumer Electronics Show, January 7–10, 1982, in Las Vegas). It has been listed in the Guinness ...
, a demo effect may make the target machine do things that are supposedly beyond its capabilities. The ability to creatively overcome major technical limitations is greatly appreciated among demosceners. Modern demos are not as focused on effects as the demos of the 1980s and 1990s. Effects are rarely stand-alone content elements anymore, and their role in programmer showcase has diminished, particularly in PC demos. As for today, PC demosceners are more likely to demonstrate their programming skills with
procedural content generation In computing, procedural generation is a method of creating data algorithmically as opposed to manually, typically through a combination of human-generated assets and algorithms coupled with computer-generated randomness and processing power. In ...
or 3D engine features than with superior visual effects.


Hardware considerations

There are demos written for many different devices that vary considerably in their graphical features and data processing capabilities. The variability in hardware also reflects in types of effects invented for each platform as well as in the methods used in the implementation. The demoscene took off on home computers such as the
Commodore 64 The Commodore 64, also known as the C64, is an 8-bit home computer introduced in January 1982 by Commodore International (first shown at the Consumer Electronics Show, January 7–10, 1982, in Las Vegas). It has been listed in the Guinness ...
and the
Amiga Amiga is a family of personal computers introduced by Commodore in 1985. The original model is one of a number of mid-1980s computers with 16- or 32-bit processors, 256 KB or more of RAM, mouse-based GUIs, and significantly improved graphi ...
, which had relatively advanced and very "hackable" custom chips and CPUs. Before the widespread use of advanced computer aided design for
integrated circuits An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuits on one small flat piece (or "chip") of semiconductor material, usually silicon. Large numbers of tiny ...
, chips were designed by hand and so often had many undocumented or unintended features. A lack of standardisation also meant that hardware design tended to reflect the designers own ideas and creative flair. For this reason, most "old school" demo effects were based on the creative exploitation of the features of particular hardware. A lot of effort was put into the
reverse-engineering Reverse engineering (also known as backwards engineering or back engineering) is a process or method through which one attempts to understand through deductive reasoning how a previously made device, process, system, or piece of software accompli ...
of the hardware in order to find undocumented possibilities usable for new effects. The
IBM PC The IBM Personal Computer (model 5150, commonly known as the IBM PC) is the first microcomputer released in the IBM PC model line and the basis for the IBM PC compatible de facto standard. Released on August 12, 1981, it was created by a team ...
compatibles of the 1990s, however, lacked many of the special features typical for the home computers, instead using standard parts. This was compensated for with a greater general-purpose computing power. The possibility of advanced hardware trickery was also limited by the great variability of PC hardware. For these reasons, the PC democoders of the
DOS DOS is shorthand for the MS-DOS and IBM PC DOS family of operating systems. DOS may also refer to: Computing * Data over signalling (DoS), multiplexing data onto a signalling channel * Denial-of-service attack (DoS), an attack on a communicat ...
era preferred to focus on pixel-level software rendering algorithms. Democoders have often looked for challenge and respect by "porting" effects from one platform to another. For example, during the "golden age" of the Amiga demos, many well-known Amiga effects were remade with
Atari ST The Atari ST is a line of personal computers from Atari Corporation and the successor to the Atari 8-bit family. The initial model, the Atari 520ST, had limited release in April–June 1985 and was widely available in July. It was the first pers ...
, Commodore 64 and PC, some of which were considered inferior in the key features required in the effects in question. Since the mid-1990s, when the PC had become a major platform, demos for the Amiga and the C-64 started to feature PC-like "pixel effects" as well.


Early history

The earliest computer programs resembling demo effects predate the demoscene for several decades. Perhaps the earliest example of these so-called
display hack A screensaver (or screen saver) is a computer program that blanks the display screen or fills it with moving images or patterns when the computer has been idle for a designated time. The original purpose of screensavers was to prevent phosphor ...
s is a program called ''Bouncing Ball'' on the Whirlwind computer in the early 1950s. Another famous display hack, '' munching squares'', was originally created on the
PDP-1 The PDP-1 (''Programmed Data Processor-1'') is the first computer in Digital Equipment Corporation's PDP series and was first produced in 1959. It is famous for being the computer most important in the creation of hacker culture at Massachusetts ...
in ca. 1962.


"Old school" effects

These effects were typical in the 1980s and the early 1990s and were first implemented on either the Commodore 64, Atari ST or the Amiga. They often relied on the systems custom hardware or were considered difficult because of it. For example, 3D objects rendered in dots are somewhat tricky on systems without byte-per-pixel displays or limited video memory bandwidth, or systems with slow and/or limited (e.g. 8 bit, no FPU) CPUs. *
Raster bar The raster bar (also referred to as rasterbar or copperbar) is an effect used in demos and older video games that displays animated bars of colour, usually horizontal, which additionally might extend into the border, a.k.a. the otherwise unalte ...
s, also called copper bars on the Amiga. * Scrollers of various kinds. * Moving sprites, with the competition usually focused on the number of visible sprites per frame. * Starfields, such as parallax-scrolling and perspective starfields. * Smooth horizontal waving of graphics images in a per-scanline basis * Shadebobs *
Infinite bobs Infinite may refer to: Mathematics *Infinite set, a set that is not a finite set * Infinity, an abstract concept describing something without any limit Music * Infinite (group), a South Korean boy band *''Infinite'' (EP), debut EP of American ...
* Plasma effect * Kefrens bars * Moire patterns, particularly circles * Text zoomers * Simple rotating 3D objects rendered in dots, lines or filled polygons. *
Spline effect Spline may refer to: Mathematics * Spline (mathematics), a mathematical function used for interpolation or smoothing * Smoothing spline, a method of smoothing using a spline function Devices * Spline (mechanical), a mating feature for rotating e ...
*
Vector graphics Vector graphics is a form of computer graphics in which visual images are created directly from geometric shapes defined on a Cartesian plane, such as points, lines, curves and polygons. The associated mechanisms may include vector display a ...
** Glenz, partially see-through models with a "diamond-like" look. First seen in the "Transformer" part of Kefrens' "Megademo 8", coded by Promax. Named by Photonhttp://eab.abime.net/showpost.php?s=37be17e022def6d7a146dfc49fc05b8e&p=461890&postcount=8 from the Swedish word "Gläns" (glisten or glitter) ** Blenk, shiny metallic aluminum-like models, from Swedish "Blänk" (shiny), also named by Photon ** Rubber, Twisting and/or elastic models. Also sometimes referred to as Gel


Chunky-pixel effects

Effects based on software rendering into chunky-pixel
framebuffer A framebuffer (frame buffer, or sometimes framestore) is a portion of random-access memory (RAM) containing a bitmap that drives a video display. It is a memory buffer containing data representing all the pixels in a complete video frame. Modern ...
s were typical in the mid and late 1990s and were usually first implemented on the PC or Falcon030. They became popular as systems with pixel-addressable high speed video memory and faster processors (to allow for more demanding real-time calculations) became common. * Effects based on static screen-to-texture lookup tables ** Texture-mapped tunnels and other objects rotating around their axis of symmetry ** Wobblers, rotators and other similar effects for 2D images ** Objects that reflect or refract underlying bitmap images * Texture-mapped tunnel with freely moving camera, typically based on realtime raytracing * Rotozoomer * Mandelbrot zoomer *
Fire effect Fire is the rapid oxidation of a material (the fuel) in the exothermic chemical process of combustion, releasing heat, light, and various reaction products. At a certain point in the combustion reaction, called the ignition point, flames are pr ...
and other effects based on 2D filters and feedback * Heightfield landscape (often called "
voxel In 3D computer graphics, a voxel represents a value on a regular grid in three-dimensional space. As with pixels in a 2D bitmap, voxels themselves do not typically have their position (i.e. coordinates) explicitly encoded with their values. Ins ...
landscape") * 2D
bump mapping Bump mapping is a texture mapping technique in computer graphics for simulating bumps and wrinkles on the surface of an object. This is achieved by perturbing the surface normals of the object and using the perturbed normal during lighting cal ...
*
Metaballs In computer graphics, metaballs are organic-looking ''n''-dimensional isosurfaces, characterised by their ability to meld together when in close proximity to create single, contiguous objects. In solid modelling, polygon meshes are commonly ...
Some of these effects were later ported to
planar Planar is an adjective meaning "relating to a plane (geometry)". Planar may also refer to: Science and technology * Planar (computer graphics), computer graphics pixel information from several bitplanes * Planar (transmission line technologies), ...
pixel machines such as the
Amiga Amiga is a family of personal computers introduced by Commodore in 1985. The original model is one of a number of mid-1980s computers with 16- or 32-bit processors, 256 KB or more of RAM, mouse-based GUIs, and significantly improved graphi ...
, without relying on chunky to planar conversion. For example, the group Sanity implemented a rotozoomer using a combination of pre-rendered planar bitmaps and
copper Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkis ...
effects.


3D rendering

3D computer graphics 3D computer graphics, or “3D graphics,” sometimes called CGI, 3D-CGI or three-dimensional computer graphics are graphics that use a three-dimensional representation of geometric data (often Cartesian) that is stored in the computer for th ...
has been featured in demos since the late 1980s. Nowadays, a general-purpose 3D engine is an integral part of most new demos. In the late 1980s and early 1990s, rotating 3D objects were considered effects in their own right due to the difficulty of calculating and rendering them. In particular, most systems did not have a floating point unit. Rather than general-purpose 3D algorithms, democoders often used special-purpose tricks highly optimized for the rotation and rendering of a particular object such as a
cube In geometry, a cube is a three-dimensional solid object bounded by six square faces, facets or sides, with three meeting at each vertex. Viewed from a corner it is a hexagon and its net is usually depicted as a cross. The cube is the only r ...
or a
sphere A sphere () is a Geometry, geometrical object that is a solid geometry, three-dimensional analogue to a two-dimensional circle. A sphere is the Locus (mathematics), set of points that are all at the same distance from a given point in three ...
. Since even drawing dots, lines or filled polygons was a difficult task in itself competition often revolved around simply optimising the drawing routines while using pre-calculated maths. To a casual viewer, many demo effects look like something attainable by a general-purpose 3D engine. However, classic effects with an apparent 3D look often have no real-time 3D calculation whatsoever. For example, static screen-to-texture look-up tables can be used with symmetrical 3D objects that rotate around their axis of symmetry. Before the advent of mass-marketed 3D acceleration hardware, democoders often focused on lighting and shading techniques in software 3D engines, including
Gouraud shading Gouraud shading, named after Henri Gouraud, is an interpolation method used in computer graphics to produce continuous shading of surfaces represented by polygon meshes. In practice, Gouraud shading is most often used to achieve continuous li ...
,
Phong shading In 3D computer graphics, Phong shading, Phong interpolation, or normal-vector interpolation shading is an interpolation technique for surface shading invented by computer graphics pioneer Bui Tuong Phong. Phong shading interpolates surface norm ...
,
texture mapping Texture mapping is a method for mapping a texture on a computer-generated graphic. Texture here can be high frequency detail, surface texture, or color. History The original technique was pioneered by Edwin Catmull in 1974. Texture mapping ...
,
bump mapping Bump mapping is a texture mapping technique in computer graphics for simulating bumps and wrinkles on the surface of an object. This is achieved by perturbing the surface normals of the object and using the perturbed normal during lighting cal ...
,
environment mapping In computer graphics Computer graphics deals with generating images with the aid of computers. Today, computer graphics is a core technology in digital photography, film, video games, cell phone and computer displays, and many specialized a ...
, radiosity and even real-time ray tracing. General-purpose 3D engines are very seldom called "effects", although the rendered scenes often contain something that can be regarded as such.


See also

*
Display hack A screensaver (or screen saver) is a computer program that blanks the display screen or fills it with moving images or patterns when the computer has been idle for a designated time. The original purpose of screensavers was to prevent phosphor ...
*
Algorithmic art Algorithmic art or algorithm art is art, mostly visual art, in which the design is generated by an algorithm. Algorithmic artists are sometimes called ''algorists''. Overview Algorithmic art, also known as computer-generated art, is a subset o ...


References

{{DEFAULTSORT:Demo Effect * Demoscene