"johns" <johns321@[EMAIL PROTECTED]
> wrote in message
news:c889124f-3fa8-41fb-9db5-ddf10c558c3f@[EMAIL PROTECTED]
>> I think you have the term "ray tracing" confused with
>> the concept opf a "vector-scan display."
>
> Yes. What is the difference?
Two completely different things.
"Ray-tracing" is a technique used in computer graphics in
which light is modeled as individual "rays," which are mathematically
"traced" from their source, as they reflect off various objects in the
scene, and then to the viewpoint of the hypothetical viewer
or camera (or the other way around). Imagine starting with a particular
spectrum and intensity of light, and both are modified as the rays
are reflected by the objects in their path. Do this with a very large
number of rays, and you can get a very good-looking image including
natural-appearing reflections, shadows, and so forth. It can also produce
accurate modeling of refractive effects - e.g., the appearance of objects
as seen through a lens, or water. (It turns out that the "rays" are most
commonly traced from the supposed viewer or camera point back to the
source, rather than vice-versa, for reasons of computational efficiency.)
A "vector-scan display" is a type of display device (now
for the most part obsolete, at least in its CRT-based form,
although there have been some laser-based displays which
are basically "vector-scan" devices). Instead of building
up an image as a regular pattern of lines, and varying the
intensity of the light as that pattern is scanned (as in a
raster-scan CRT), a vector-scan display works by essentially
"painting" the outlines of objects to be displayed on the screen,
typically (as noted) a fairly long-persistence CRT. This method
works very well for making clear, sharp images of a simple
"line drawing" sort, but producing images of "solid" objects
and doing full color are both virtually impossible.
Bob M.
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