In article <web.4497a173bda360d27d55e4a40@news.povray.org>, 
alp### [at] zubenelgenubi34spcom says...
> Patrick Elliott <sel### [at] rraznet> wrote:
> 
> > No it couldn't, because graphics cards ***do not*** raytrace, then
> > scanline.
> 
> I think what's actually being referred to is using the GPU (in sufficient
ly
> modern cards) as a fast vector processor that can be programmed to carry
> out arbitrary (i.e. not triangular or scanliney) calculations. I would
> actually read the headlines on that site (http://www.gpgpu.com) to see wh
at
> is being talked about. GPU pipelines are still single-precision though, a
nd
> POVRay uses double-precision maths throughout. It would be a massive job 
in
> any case, and easier to buy more CPUs.
> 
Ah.. Yeah, that could be it. Not that one couldn't sacrifice "some" 
precision to gain speed that way, but it wouldn't be the same result. 
Though.. It does provide an interesting solution if you want to create a 
game based renderer that uses POV-Ray like function, but not quite the 
same level of accuracy. Not sure how much it would truly improve the 
speed though. If it could let you do refraction and reflection in a few 
seconds on a complex scene, instead of minutes, it might be worth it for 
an idea I had, but I wouldn't expect real time from it. lol

> > That is the other thing you don't get. At some point you still have to
> > do the math. You can do it the way POV-Ray does and produce "exact"
> > mathematical versions, or you can use the math the generate
> > "approximations" that the GPU can handle. And it will always be an
> > approximation. You can't do true physical models of real world objects,
> > which are "not" made up of bunches of triangles
> 
> I don't agree. Raytracing is absolutely an approximation (e.g. no forward
> light without photon maps, ignores wave physics of light, etc). Also, the
> use of triangles is a separate issue (you can clearly raytrace triangles)
.
> I would say that real-world objects are not made up of any sort of
> primitive that POVRay or other renderers use, triangles included.
> Certainly, I've never seen a perfect box{} in the real world (checks
> furniture).
> 
If you want to be picky, then yes. The point though is that between the 
two approximations, true raytracing is closest to reality, even if you 
have to round the edges of some things to make them, "not perfect 
boxes". And the overhead... Like I have told several people, what you 
can do in about 50 lines of POV-Ray code would take a 1.5MB mesh file, 
not including textures, on most GPU based systems. From a purely 
practical standpoint, GPUs are not practical for photorealism, even if 
they are currently faster at producing results.

-- 
void main () {

    call functional_code()
  else
    call crash_windows();
}

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