Perhaps he really is looking for Ray Casting (in the context of surfaces,
versus volumes) if he's looking for an alternative to Ray Tracing.

http://en.wikipedia.org/wiki/Ray_casting

Excerpt:
Ray casting is not a synonym for ray
tracing<http://en.wikipedia.org/wiki/Ray_tracing_%28graphics%29>,
but can be thought of as an abridged, and significantly faster, version of
the ray tracing algorithm. Both are image
order<http://en.wikipedia.org/wiki/Image_and_object_order_rendering>algorithms
used in computer
graphics <http://en.wikipedia.org/wiki/Computer_graphics> to
render<http://en.wikipedia.org/wiki/Rendering_%28computer_graphics%29>three
dimensional scenes to two dimensional screens by following
rays <http://en.wikipedia.org/wiki/Ray_%28optics%29> of
light<http://en.wikipedia.org/wiki/Light>from the
eye <http://en.wikipedia.org/wiki/Projective_geometry> of the observer to a
light source. Ray casting does not compute the new direction a ray of light
might take after intersecting a surface on its way from the eye to the
source of light. This eliminates the possibility of accurately rendering
reflections <http://en.wikipedia.org/wiki/Reflection_%28physics%29>,
refractions <http://en.wikipedia.org/wiki/Refractions>, or the natural
falloff of shadows <http://en.wikipedia.org/wiki/Shadow>; however all of
these elements can be faked to a degree, by creative use of
texture<http://en.wikipedia.org/wiki/Texture_%28computer_graphics%29>maps
or other methods. The high speed of calculation made ray casting a
handy rendering method in early real-time 3D video games.


-Rob


On Mon, Feb 1, 2010 at 3:17 AM, Chris Barber <chris at cb1inc.com> wrote:

>  Do you mean ray marching? http://en.wikipedia.org/wiki/Volume_ray_casting
>
> *
>
> *
> On 1/31/10 11:53 PM, Ryan Hanson wrote:
>
> To the people who went to the penguins unbound thingy on Saturday.
> I'm trying to figure out the other alternative to Ray Tracing that used
> stepping.
>
> I tried searching for Ray Stepping but I didn't find anything.
>
> Any help?
>
> Thanks
>
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