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The docs say that the cylinder light syntax is exactly like the spotlight
syntax. How can this be so? The radius keyword in the spotlight is the
radius angle of the cone surface from the reflective vector. There is no
such thing for a cylinder. Same with the falloff keyword.
What effect do these keywords have on a cylinder light? When toying with
it, it seems that the falloff has the most effect on the look of the light,
and radius seems to have no effect. Anyway, you get the idea. How is the
cylinder light supposed to be used?
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On Wed, 6 Feb 2002 11:53:21 -0500, "cadman" <cad### [at] graffiti net> wrote:
> How is the
> cylinder light supposed to be used?
I think it could be better if you send such question to
povray.documentation.inbuilt or povray.newuser.
(note - theres is example of how it should be used in insert menu)
The only bug-kind thing I can find it this subject is: there is no example for
cylinder light in /scenes/lights directory.
ABX
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From: Felix Wiemann
Subject: Re: Looking for more info on cylinder lights
Date: 6 Feb 2002 14:47:20
Message: <3c618848@news.povray.org>
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> I think it could be better if you send such question to
> povray.documentation.inbuilt or povray.newuser.
>
> (note - theres is example of how it should be used in insert menu)
>
> The only bug-kind thing I can find it this subject is: there is no example
for
> cylinder light in /scenes/lights directory.
>
> ABX
The doc should be understandable by new users. I think the whole section
should be changed, but perhaps that's better discussed in p.d.inbuilt.
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I found the section on cylinder lights bewildering too.
"Felix Wiemann" <Fel### [at] gmxnet> wrote in message
news:3c618848@news.povray.org...
> > I think it could be better if you send such question to
> > povray.documentation.inbuilt or povray.newuser.
> >
> > (note - theres is example of how it should be used in insert menu)
> >
> > The only bug-kind thing I can find it this subject is: there is no
example
> for
> > cylinder light in /scenes/lights directory.
> >
> > ABX
>
> The doc should be understandable by new users. I think the whole section
> should be changed, but perhaps that's better discussed in p.d.inbuilt.
>
>
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On Wed, 6 Feb 2002 11:53:21 -0500, "cadman" <cad### [at] graffitinet>
wrote:
>The docs say that the cylinder light syntax is exactly like the spotlight
>syntax.
It is.
>How can this be so?
Because they act exactly the same from the point of emission to the
point_at point.
>The radius keyword in the spotlight is the radius angle of the cone
>surface from the reflective vector. There is no such thing for a cylinder.
There is, it is the visible angle, as seen from the point of emission,
of the cross-section of the cylinder containing the point_at point.
Simple, eh? :))
>Same with the falloff keyword.
Exactly.
>What effect do these keywords have on a cylinder light? When toying with
>it, it seems that the falloff has the most effect on the look of the light,
>and radius seems to have no effect. Anyway, you get the idea. How is the
>cylinder light supposed to be used?
A cylinder light *is* a spotlight, from the point of view of
controlling parameters and lighting behaviour. The only difference is
that the cone of light is trimmed with an infinite cylinder, but this
does not affect the light distribution within it. The axis of this
cylinder is colinear with the vector between the emission point and
point_at, and the radius of the cylinder is exactly the radius of the
cone at its focal plane (if that could be said for a spotlight :) )
If my babblings make it more clear, then the docs could use a
refreshment.
Peter Popov ICQ : 15002700
Personal e-mail : pet### [at] vipbg
TAG e-mail : pet### [at] tagpovrayorg
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in news:ibl46u8d5hlp57c9qeek37243llng00l4l@4ax.com Peter Popov wrote:
> There is, it is the visible angle, as seen from the point of emission,
> of the cross-section of the cylinder containing the point_at point.
> Simple, eh? :))
>
Peter, I have a problem visualising this and the rest of the cylinder
light. Could you illustrate it with a sketch?
Ingo
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>
> If my babblings make it more clear, then the docs could use a
> refreshment.
Scary as it may seem, your babblings make sense. To a simple man such as
myself, it would be better to revamp the cylinder light syntax such that it
makes sense, rather than refresh the docs. E.g. the radius keyword would
specify the radius of the cyliner, as would falloff. This would seem to
make for a lot less math to figure "The axis of this cylinder is colinear
with the vector between the emission point and point_at, and the radius of
the cylinder is exactly the radius of the cone at its focal plane (if that
could be said for a spotlight :) )"
Thanks for listening.
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On 7 Feb 2002 16:11:45 -0500, ingo <ing### [at] homenl> wrote:
>Peter, I have a problem visualising this and the rest of the cylinder
>light. Could you illustrate it with a sketch?
I'll try rendering something tomorrow (it's 1:17 am now, yawn)
Peter Popov ICQ : 15002700
Personal e-mail : pet### [at] vipbg
TAG e-mail : pet### [at] tagpovrayorg
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It was pointed out to me that cylinder lights in 3.5 are true
cylinders and not what they were in 3.1. I did some tests (visualized
them in media) and it seems to me to be so. So y'all might as well
forget about my babblings unless you need 3.1 clarified ;)
Peter Popov ICQ : 15002700
Personal e-mail : pet### [at] vipbg
TAG e-mail : pet### [at] tagpovrayorg
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Indeed...
So what does the radius keyword mean, then? I pointed a cylinder light at a
plane with concentric rings @ 1 unit intervals, and changing the radius
corresponded to about 1/10 of a unit hotspot. Does this seem confusing to
anyone else?
"Peter Popov" <pet### [at] vipbg> wrote in message
news:hkia6ugh4oe010bf4f70t1d5km1t5mianp@4ax.com...
> It was pointed out to me that cylinder lights in 3.5 are true
> cylinders and not what they were in 3.1. I did some tests (visualized
> them in media) and it seems to me to be so. So y'all might as well
> forget about my babblings unless you need 3.1 clarified ;)
>
>
> Peter Popov ICQ : 15002700
> Personal e-mail : pet### [at] vipbg
> TAG e-mail : pet### [at] tagpovrayorg
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