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Alain <ele### [at] netscape net> wrote:
> Gravity lense, in any direction not directly aimed at it's center.
Except that gravity does not make anything go in a circular path except
in very exceptional circumstances (which in case of light could happen
only at a certain distance from a black hole).
--
- Warp
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In article <4400447f@news.povray.org>, war### [at] tagpovrayorg says...
> Nekar Xenos <go_### [at] yahoocom> wrote:
> > I meant to replace my intitial suggestion with the second one. Is it not
> > possible to test intersection of a circle with an object? Please excuse me,
> > but I (obviosly)don't know how a raytracer is programmed. How is
> > intersection of a straight ray done? I was thinking of just replacing the
> > formula for the straight ray with the formula of a circle.
>
> How would a ray travelling in a circular path be any feasible way of
> emulating variable ior? I'm not even sure it's physically possible to
> have an object with an ior such that light travels in a circular path
> through it regardless of the direction.
>
Now... A Spline Path could work though, maybe? I mean your basically just
doing the same thing you do with any object, make a determination of
where it is likely to intersect. I am sure you could find some averaging
function to determine where the bounding box intersection is for a
"straight" line that would hit the same point. As well as something to
find the final "direction". If no other objects are intersected, you just
continue the ray from that final point on the surface of the object. If
intersection tests of a bounding box for something inside is detected,
then you calculate along the spline path, until you hit. When it leaves
the interior of the object you stop doing the extra calculations and
continue on a normal strait path.
Or something more or less like that. The only real question is, given an
object, can you determine an averaged IOR for the ray and a final
direction, allowing you to shortcut the calculations when no
intersections are possible. Of course, I don't know how media might be
effected by such a thing...
--
void main () {
call functional_code()
else
call crash_windows();
}
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Patrick Elliott <sha### [at] hotmailcom> wrote:
> Now... A Spline Path could work though, maybe?
And sampling along a spline (iow. splitting the spline into very small
parts and making a whole ray-scene intersection test for each small part)
is exactly what would make it prohibitively slow.
Would it really be worth the effort?
Radiosity requires lots of sampling, but the results can be spectacular.
Media also requires lots of sampling, but the results can also be quite
spectacular. Variable IOR would probably require even more sampling, yet
I highly doubt the end result will look any spectacular.
--
- Warp
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"Warp" <war### [at] tagpovrayorg> wrote in message
news:44014e05@news.povray.org...
> Patrick Elliott <sha### [at] hotmailcom> wrote:
>> Now... A Spline Path could work though, maybe?
>
> And sampling along a spline (iow. splitting the spline into very small
> parts and making a whole ray-scene intersection test for each small part)
> is exactly what would make it prohibitively slow.
> Would it really be worth the effort?
>
> Radiosity requires lots of sampling, but the results can be spectacular.
> Media also requires lots of sampling, but the results can also be quite
> spectacular. Variable IOR would probably require even more sampling, yet
> I highly doubt the end result will look any spectacular.
>
> --
> - Warp
Heat haze, bullet trails and sunsets can all be quite spectacular. I tried
doing a planetary scene coming in from outer space and landing on the
planet. I got double sun mirages at stages, maybe variable ior could have
fixed it?
--
-Nekar Xenos-
----------------------------------------
"The truth is out there..."
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Among other things, Warp saw fit to write:
> And sampling along a spline (iow. splitting the spline into very small
> parts and making a whole ray-scene intersection test for each small part)
> is exactly what would make it prohibitively slow.
> Would it really be worth the effort?
>
> Radiosity requires lots of sampling, but the results can be spectacular.
> Media also requires lots of sampling, but the results can also be quite
> spectacular. Variable IOR would probably require even more sampling, yet
> I highly doubt the end result will look any spectacular.
Could it maybe be "faked" in some way, similarly to how the caustics keyword
fakes photons?
I'm not sure what kind of effect it would give, I'm just throwing some white
noise into the discussion :-)
--
light_source{9+9*x,1}camera{orthographic look_at(1-y)/4angle 30location
9/4-z*4}light_source{-9*z,1}union{box{.9-z.1+x clipped_by{plane{2+y-4*x
0}}}box{z-y-.1.1+z}box{-.1.1+x}box{.1z-.1}pigment{rgb<.8.2,1>}}//Jellby
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In article <44014e05@news.povray.org>, war### [at] tagpovrayorg says...
> Patrick Elliott <sha### [at] hotmailcom> wrote:
> > Now... A Spline Path could work though, maybe?
>
> And sampling along a spline (iow. splitting the spline into very small
> parts and making a whole ray-scene intersection test for each small part)
> is exactly what would make it prohibitively slow.
> Would it really be worth the effort?
>
But, is it actually slower than for a regular line? I mean, sure, the
calculation may require a few more math steps, but intersections still
require the same sort of testing, even for a straight line right? Maybe I
am wrong.
> Radiosity requires lots of sampling, but the results can be spectacular.
> Media also requires lots of sampling, but the results can also be quite
> spectacular. Variable IOR would probably require even more sampling, yet
> I highly doubt the end result will look any spectacular.
>
Depends. What about an object where the variable IOR is based on a
pattern, similar to what you can do with media? Right now you can't even
simulate that, at least unless you wanted to glue together hundreds of
discrete objects, all approximate shapes and all with different IORs. We
really can't be sure what effect would result, without trying it. And for
that matter, from what I understand, there are real world materials that
actually have a "different" IOR depending on the angle of incidence of
the light hitting it (I think I remember reading about some anyway).
--
void main () {
call functional_code()
else
call crash_windows();
}
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In article <l2l### [at] badulaqueunexes>, me### [at] privacynet says...
> Among other things, Warp saw fit to write:
>
> > And sampling along a spline (iow. splitting the spline into very small
> > parts and making a whole ray-scene intersection test for each small part)
> > is exactly what would make it prohibitively slow.
> > Would it really be worth the effort?
> >
> > Radiosity requires lots of sampling, but the results can be spectacular.
> > Media also requires lots of sampling, but the results can also be quite
> > spectacular. Variable IOR would probably require even more sampling, yet
> > I highly doubt the end result will look any spectacular.
>
> Could it maybe be "faked" in some way, similarly to how the caustics keyword
> fakes photons?
>
> I'm not sure what kind of effect it would give, I'm just throwing some white
> noise into the discussion :-)
>
Well, as I pointed out in a reply, yeah, for some cases, others, like a
complex pattern based IOR would be either impossible or prohibitively
complex to manage, nor could any simulation deal with materials with odd
properties, like IOR differing by the angle light enters.
--
void main () {
call functional_code()
else
call crash_windows();
}
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Patrick Elliott <sha### [at] hotmailcom> wrote:
> But, is it actually slower than for a regular line? I mean, sure, the
> calculation may require a few more math steps, but intersections still
> require the same sort of testing, even for a straight line right? Maybe I
> am wrong.
You have to test a straight line against the scene once. A spline would
have to be tested hundreds or thousands of times.
--
- Warp
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Warp wrote:
> Radiosity requires lots of sampling, but the results can be spectacular.
> Media also requires lots of sampling, but the results can also be quite
> spectacular. Variable IOR would probably require even more sampling, yet
> I highly doubt the end result will look any spectacular.
This is probably the best argument against it I've heard. I'm sure
someone will eventually write a patch to do it, and we'll see at that
point whether your argument is justified.
Personally, I think that if used well, it could aid in realism the same
way that radiosity, focal blur, et al can - that is, when the viewer
doesn't realize that the effect is there, that's when it has the
greatest benefit.
...Chambers
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Warp nous apporta ses lumieres en ce 27/02/2006 01:09:
> Patrick Elliott <sha### [at] hotmailcom> wrote:
>
>>But, is it actually slower than for a regular line? I mean, sure, the
>>calculation may require a few more math steps, but intersections still
>>require the same sort of testing, even for a straight line right? Maybe I
>>am wrong.
>
>
> You have to test a straight line against the scene once. A spline would
> have to be tested hundreds or thousands of times.
>
You'd need some spacing for the tests. To small and it takes for ever. To large and
you can go right
trough several objects. Then, it a test get inside an object, take a new point between
the last and
next to last, test again until you reach a sufficient confidence value.
It will take very long if you only have simple primitives, and now the fun beggin when
you add
torus, superellipsoids, sphere_sweeps and the nightmare is on you as soon as you add
some
isosurfaces. And you *think* that radiosity with photons, scathering media,
reflections and
transparcy, togheter with many area_lights, and area_light photons make for long
render time? Does
anybody have a cluster of 100GHz computers at hand?
--
Alain
-------------------------------------------------
REMEMBER: WHATEVER HAPPENS, HAPPENS FOR A REASON.
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