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Amiga Plus Extra 1996 #6
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AmigaPlus-eXtra-6-96.iso.7z
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programme
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a-render
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ray_tracing.doc
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1987-03-22
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What is Ray Tracing ?
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The basic idea of ray tracing is to trace light rays through a scene
to determine the visibility of an object on the screen. The object
is then shaded according to surface characteristics and each light's color
and location.
Ray tracing is based on the principles of light and optics. It is used
to create extremely complex pictures in true 3-D. The pictures get their
realism from the reflections and refractions ray-tracing generates by
following the laws of optics.
The way that you describe your picture is by building what we call
'objects' in 3-D. 3-D means that the objects have width, height, and
depth. It means objects can be close and look larger, or distant and
smaller. After you have built some objects, you place them in the 3-D
world. This means each object has a location, size, and rotation. After
you describe this information, and your lights, you are ready to 'render'
the scene.
Since the number of light rays entering a scene may be considered
infinite, a shortcut is used, namely, tracing the light rays backwards thru
the scene. With this method, a ray is traced from the eye, through a pixel
in the view plane (the monitor screen) and intersected with the objects in
the 3-D world. Of the objects that do intersect the viewing ray, the
visible surface would be the one that is closest to the eye and therefore
is the one that we shade according to the lights. This process is repeated
for each pixel in the view plane. See LIGHT.DOC for details on the shading
process.
With ray tracing, while we can describe objects to the computer, and
generate images that look quite real, remember that these objects do not
need to exist at all, a 'world' can be created in your computer's memory
that exists nowhere else.
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Brief history of the development of ray-tracing:
Who have been the researchers in the ray-tracing field ?
- The major researchers of this sort of graphic program have traditionally
been major colleges and companies.
Who have been the people to use ray-tracing the most?
- Today's major applications of ray-tracing are commercial production
(TV commercials and movies) and mechanical design for industrial
use. Industry analysts predict a far greater usage in design (CAD/CAM)
areas than in production applications. Medical applications are also
growing.
There have been a small number of researchers in this field.
- The number of researchers making major contributions in this area has
been small, and they have names like Phong, Whitted, Sutherland,
Sproull, Gouraud, Hall, Catmull, Greenberg, Blinn, and Crow. See the
references listed for more info on their juicy papers, but be ready to
put on your thinking cap. Try your nearest University library first.