Page 154 - DCAP104_EXPOSURE_TO_COMPUTER_DISCPLINES

Unit 7: Graphics and Multimedia

Hypertext languages are not graphics file formats, like the GIF or DXF formats. Instead, they are Notes
programming languages, like PostScript or C. As such, they are specifically designed for serial
data stream transmission. That is, you can start decoding a stream of hypertext information as
you receive the data. You need not wait for the entire hypertext document to be downloaded
before viewing it.
The term hypermedia refers to the marriage of hypertext and multimedia. Modern hypertext
languages and network protocols support a wide variety of media, including text and fonts, still
and animated graphics, audio, video, and 3D data. Hypertext allows the creation of a structure
that enables multimedia data to be organized, displayed, and interactively navigated through
by a computer user.
Hypertext and hypermedia systems, such as the World Wide Web, contain millions of information
resources stored in the form of GIF, JPEG, PostScript, MPEG, and AVI files. Many other formats
are used as well.
7.3.10 3D Formats

Three-dimensional data files store descriptions of the shape and color of 3D models of imaginary
and real-world objects. 3D models are typically constructed of polygons and smooth surfaces,
combined with descriptions of related elements, such as color, texture, reflections, and so on, that
a rendering application can use to reconstruct the object. Models are placed in scenes with lights
and cameras, so objects in 3D files are often called scene elements.

Rendering applications that can use 3D data are generally modeling and animation programs,
such as NewTek’s Lightwave and Autodesk’s 3D Studio. They provide the ability to adjust the
appearance of the rendered image through changes and additions to the lighting, textures applied
to scene elements, and the relative positions of scene elements. In addition, they allow the user
to animate, or assign motions to, scene elements. The application then creates a series of bitmap
files, or frames, that taken in sequence can be assembled into a movie.

It’s important to understand that vector data historically has been 2D in nature. That is, the creator
application with which the data originated made no attempt to simulate 3D display through the
application of perspective. Examples of vector data include CAD drawings and most clip art
designed to be used in desktop publishing applications. There is a certain amount of confusion in
the market about what constitutes 3D rendering. This is complicated by the fact that 3D data is now
supported by a number of formats that previously stored only 2D vector data. An example of this
is Autodesk’s DXF format. Formats like DXF are sometimes referred to as extended vector formats.
7.3.11 Virtual Reality Modeling Language (VRML) Formats

VRML (pronounced “vermel”) may be thought of as a hybrid of 3D graphics and HTML. VRML
v1.0 is essentially a subset of the Silicon Graphics Inventor file format and adds to it support for
linking to Uniform Resource Locators URLs in the World Wide Web.
VRML encodes 3D data in a format suitable for exchange across the Internet using the Hypertext
Transfer Protocol (HTTP). VRML data received from a Web server is displayed on a Web browser
that supports VRML language interpretation. We expect that VRML-based 3D graphics will soon
be very common on the World Wide Web.
This book does not contain an in-depth discussion of VRML for some of the same reasons that we
do not provide detailed descriptions of hypertext, hypermedia, and 3D formats.
7.3.12 Audio Formats

Audio is typically stored on magnetic tape as analog data. For audio data to be stored on media
such as a CD-ROM or hard disk, it must first be encoded using a digital sampling process similar

LOVELY PROFESSIONAL UNIVERSITY 147