|Principle: rays are cast and traced
in groups based on some geometric constraints. For instance:
on a 320x200 display resolution, a ray-caster traces only 320 rays
(the number 320 comes from the fact that the display has 320 horizontal
pixel resolution, hence 320 vertical column).
||Principle: each ray is traced
separately, so that every point (usually a pixel) on the
display is traced by one ray. For instance: on a 320x200 display
resolution, a ray-tracer needs to trace 320x200 (64,000) rays. (That
is roughly 200 times slower than ray-casting.)
|Formula: in most cases, inexact.
||Formula: in most cases, exact.
|Speed: very fast compared to ray-tracing;
suitable for real time process.
||Speed: slow; unsuitable for real
time process (at least not until we got a 500Ghz machine).
|Quality: resulting image is not
very realistic. Often, they are blocky (Figure
||Quality: resulting image is very
realistic - sometimes too realistic (Figure 4).
|World: limited by one or more
geometric constraints (simple geometric shapes).
||World: almost any shape can be
|Storage: small. Rendered images
are not stored on disk. Normally, only the map is stored, and corresponding
images are generated "on the fly."
||Storage: Rendered images are stored
on disk and loaded when needed. Presently, no hardware is fast enough
for "on the fly" rendering.
|Examples: Wolfenstein 3D (iD Software),
Shadow Caster (Raven), Arena (Bethesda), Doom (iD Software), Dark
||Examples: Examples: 7th Guest
(Trilobyte), Critical Path (Mechadeus), 11th Hour (Trilobyte), Myst
(Cyan), Cyberia (Xatrix).
Scene from Wolfenstein 3D (iD Software). Notice the blocky look.
The objects (gun) and enemies (a dog) are just transparent bitmaps
being scaled and blitted (i.e.: pasted) over the background.|
Scene from the game 7th Guest (Virgin Software/Trylobyte). The result
of the rendering is stunning. However, player's movement is restricted
to a pre-determined path (because the amount of pre-rendered images