[cad-linux] Re: Fwd: AECCafe News September 13

> BMRT is a true raytracer.  it does not fake it the way that=20
> renderman does=20
> even though it uses the same language.  in fact Pixar=20
> uses(they used to=20
> employ it's creator)BMRT when more accurate rending is=20
> required.  search for=20
> bmrt & bugslife.

Thanks for the info. However, raytracing only gets me halfway there. :) =
With raytracing, you get hard-line shadows, true reflections, and glass =
refractions. You don't necessarily get caustics and you certainly don't =
get 'bounced' light, where sunlight shining on a wall will light the =
whole room via transmitting of the light bouncing off it's white =
surfaces.

In other words, raytracing looks very much like being in outer-space, =
hence why a lot of 3D renderings look flat and glossy, and why when =
doing architectural 3D renderings you're forced into faking light. In =
the above example, if I'm trying to render a room with a skylight, I'll =
need two lights- one to be the sun, and the other 'fake' light to show =
the effect of the sunlight bouncing off that wall into the rest of the =
room. Seeing that I'm just guessing at the amount of light coming off =
the wall, and faking it, and can't possibly follow up and place a light =
in every location light may be bouncing, I wind up with a 'fake' =
representation of what's going on it the room. Which, if your animating =
or producing a game, is fine, but if the intent is to see if enough =
light will reach certain parts of the room then it's not much of a help.

Radiance raytraces then goes one step further; it calcs out the bouncing =
of the light around the room, so you can really just use one light, the =
sun, and don't have to fake anything. Radiance will allow you calc out =
what happens to the light in the room, it's bouncing, and even it's =
transmission through different kinds of glazing, so I can take my =
skylight into effect. It's really cool and really hard to learn :).

Here's some links if you want to check it out sometime:

Main site: http://radsite.lbl.gov/radiance/

Community site: http://www.radiance-online.org/

a company that uses Radance: http://www.visarc.com/

it's currently owned by Berkeley Livermore Labs, but will be released =
under the GPL at the end of the year.

Jeffrey McGrew

Other related posts: