distant light a la lightwave.  i'm told that lightwave has a light
source called distant light.  it acts like the sun as all of its rays
are parallel.  you specify the angle in relation to the horizontal plane
and voila, parallel light from a distance.  i think this would be much
easier than making a cylindrical light with the parallel and/or orient
keywords.  has this been thought of before?  am i in left field?

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ryan constantine <rco### [at] yahoocom> wrote:
: i think this would be much
: easier than making a cylindrical light

  Why it would be much easier? I don't have any difficulty in specifying
a cylindrical light with parallel rays.

-- 
main(i,_){for(_?--i,main(i+2,"FhhQHFIJD|FQTITFN]zRFHhhTBFHhhTBFysdB"[i]
):_;i&&_>1;printf("%s",_-70?_&1?"[]":" ":(_=0,"\n")),_/=2);} /*- Warp -*/

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In article <39FF45E7.3A076D7B@yahoo.com>, ryan constantine 
<rco### [at] yahoocom> wrote:

> distant light a la lightwave.  i'm told that lightwave has a light
> source called distant light.  it acts like the sun as all of its rays
> are parallel.  you specify the angle in relation to the horizontal plane
> and voila, parallel light from a distance.  i think this would be much
> easier than making a cylindrical light with the parallel and/or orient
> keywords.  has this been thought of before?  am i in left field?

How is specifying "parallel" and a "point_at" vector so difficult? And 
how is this "distant light" feature any different? And why are you 
trying to use a cylinderical light source? Just use a point source for 
the sun...
And "orient" doesn't have anything to do with parallel light_sources, it 
only affects area lights.

-- 
Christopher James Huff
Personal: chr### [at] maccom, http://homepage.mac.com/chrishuff/
TAG: chr### [at] tagpovrayorg, http://tag.povray.org/

<><

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Hi,

Chris Huff wrote:

> How is specifying "parallel" and a "point_at" vector so difficult? And
> how is this "distant light" feature any different? And why are you
> trying to use a cylinderical light source? Just use a point source for
> the sun...
> And "orient" doesn't have anything to do with parallel light_sources, it
> only affects area lights.

3D Studio VIZ 3 have also a kind of "parallel-spot" to simulate a sun. It
looks like a cylinderical light with a start-, end-point and a radius. I
have't used the light (cyl.) in POV before, but i don't think, that this one
can do soft shadows.

Paul

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> 3D Studio VIZ 3 have also a kind of "parallel-spot" to simulate a sun. It
> looks like a cylinderical light with a start-, end-point and a radius. I
> have't used the light (cyl.) in POV before, but i don't think, that this
one
> can do soft shadows.

It can if you add an area light attribute to it.

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Btw, it's a common misconception that light rays coming from the Sun are
parallel.

  Actually the Sun is an area light. Its size is significant and thus the
rays coming from it are not parallel. Light rays coming from opposite sides
of the Sun disk hit a point in the Earth at different angles.

  Thinking about it, there should not be big difference between a circular
light source with the radius of the Sun at a distance of the Sun from the
Earth, and a circular light source at 1km of distance and respectively
smaller radius (so that its apparent size is the same), given that our
scene is some meters wide.

-- 
main(i,_){for(_?--i,main(i+2,"FhhQHFIJD|FQTITFN]zRFHhhTBFHhhTBFysdB"[i]
):_;i&&_>1;printf("%s",_-70?_&1?"[]":" ":(_=0,"\n")),_/=2);} /*- Warp -*/

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>   Btw, it's a common misconception that light rays coming from the Sun are
> parallel.

What I don't understand is why it's so common, it should be obvious; all you
have to do is look up when there's some clouds passing by.

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In article <3a0031f5@news.povray.org>, Warp <war### [at] tagpovrayorg> 
wrote:

>   Btw, it's a common misconception that light rays coming from the Sun 
> are parallel.

It is? I have never heard of anyone saying that...only of people using 
parallel lights to simulate the large distance. Not very accurate, but 
still sometimes useful when the true scale gives precision problems.

-- 
Christopher James Huff
Personal: chr### [at] maccom, http://homepage.mac.com/chrishuff/
TAG: chr### [at] tagpovrayorg, http://tag.povray.org/

<><

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"Jetlag" <bga### [at] microsoftcom> wrote in message
news:3a008179@news.povray.org...
> >   Btw, it's a common misconception that light rays coming from the Sun
are
> > parallel.
>
> What I don't understand is why it's so common, it should be obvious; all
you
> have to do is look up when there's some clouds passing by.

    Look at the sky at sunset and wonder why the western clouds throw
shadows that -diminish- in width as they reach the opposite horizon.

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In article <3a008179@news.povray.org>, "Jetlag" <bga### [at] microsoftcom> 
wrote:

> What I don't understand is why it's so common, it should be obvious; all 
> you have to do is look up when there's some clouds passing by.

Umm, if you are talking about what I think you are(the visible "beams" 
of light caused by partial clouds and atmospheric scattering), that is a 
completely different illusion, caused by perspective. The beams appear 
to come from a point because they appear smaller and closer together the 
further away they are...the same effect that shows in railroad tracks, 
checkered planes, etc. If the light was parallel, you would still get 
that effect. I don't know how much a difference the divergence makes, 
but I doubt it would be obvious without side-by-side comparisons of 
images. It might be an interesting POV project though...

-- 
Christopher James Huff
Personal: chr### [at] maccom, http://homepage.mac.com/chrishuff/
TAG: chr### [at] tagpovrayorg, http://tag.povray.org/

<><

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