other than a cylinder
one that I can really use like aim it at a spot and have it work like a 
laser
thanks

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Attachments:
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Preview of image '7937psacantilevera.gif'

"Flaming Monarch" <fla### [at] gatescom> wrote in message
news:3CE### [at] gatescom...
> other than a cylinder
> one that I can really use like aim it at a spot and have it work like a
> laser
> thanks


Hmm... are you trying to create a light-source that will automatically
bounce off mirrors, refract, etc?

AFAIK, while mirrors do reflect objects, without advanced stuff like photons
/ rad, the light itself will not bounce (thus lighting other objects). If
all you need to achieve is the laser "effect", the cylinders might work the
most directly.

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Yes, a cylinder light will do the trick.

However, since cylinder lights are really pointlights with their effect
constrained by a cylinder, I believe they don't work as expected with
photons. That means you won't be able to make them bounce off of mirrors and
such, unless I'm mistaken.

 - Slime
[ http://www.slimeland.com/ ]

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"Slime" <slm### [at] slimelandcom> wrote in message
news:3cea9597@news.povray.org...
> Yes, a cylinder light will do the trick.
>
> However, since cylinder lights are really pointlights with their effect
> constrained by a cylinder, I believe they don't work as expected with
> photons. That means you won't be able to make them bounce off of mirrors
and
> such, unless I'm mistaken.

Actually I think it works as expected, see image.
The green cylinder is where the spot comes from. In it is a point light.
The overall light doesn't cast photons for speeds sake.

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A cylindrical light source could be better for a laser.

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> A cylindrical light source could be better for a laser.

That's what I said, cylindrical =)

Ooh, you misunderstood my "cylinder lights are really point light sources
with their effect constrained by a cylinder." What I meant by this, is that
internally, POV-Ray takes two steps to see if a point is lit by a
cylindrical light source:

1. check to see if the point is contained within the cylinder that you've
defined for the cylindrical light source.
2. if it is, check to see if there's a straight line from the point to the
light source's origin.

The problem is that all of the rays aren't parallel. Points that are very
close to the light source's position, but still inside the cylinder, might
be lit up unexpectedly because they're being lit *from the center of the
cylinder*, not parallel to the cylinder.

A cylinder light with an infinitely large cylinder behaves identically to a
regular point light source.

This works well enough normally. But when there are photons, I'm not sure
how it behaves, since photons may be reflected. It's no longer able to
perform step number one since the photons are likely to be out of the
cylinder but still legitimate, so if you put a reflective object close to
the light source, it might behave strangely. It's hard to explain what I
mean.

Here's what I mean: if you put a cylindrical light source with radius one at
the origin and shine it at a perfectly transparent plane at z=3 (with no
refraction or reflection), and make it shoot photons at that plane, I think
the other side of the plane will look like there was a point light source at
the origin, and the plane had a dark, shadow-casting pigment everywhere
except for a transparent hole with radius one at x=y=0.

Try that same image you just posted with a cylinder light source and no
actual cylinder object, and see if it still works. It might; I'm not sure.
Move the light real close to the photon reflecting object to see.

 - Slime
[ http://www.slimeland.com/ ]

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"Flaming Monarch" <fla### [at] gatescom> wrote in message
news:3CE### [at] gatescom...
> other than a cylinder
> one that I can really use like aim it at a spot and have it work like a
> laser
> thanks

IMHO you'd be better of writing macros to handle using cylinders. Any other
approach is presumably going to require scattering media (if you want the lasers
to be visible) and photons (if mirrors are involved), so render times are going
to shoot through the roof.

Now, a nice set of laser-macros that trace a path would be nice - is there a way
to return the reflection component of a surface?

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"Tom Melly" <tom### [at] tomandlucouk> wrote in message
> IMHO you'd be better of writing macros to handle using cylinders. Any other
> approach is presumably going to require scattering media (if you want the
lasers
> to be visible) and photons (if mirrors are involved), so render times are
going
> to shoot through the roof.
>
> Now, a nice set of laser-macros that trace a path would be nice - is there a
way
> to return the reflection component of a surface?
>


You could calculate if from the normal returned by trace(). . . but you probably
already knew that.

Batronyx ^"^


--
light_source{0,1}#macro c(J,a)sphere{0,1pigment{rgb z}scale a translate J+O}
#end#macro B(R,V,O)c(0,4)intersection{c(V,R)difference{c(-z*4x+10)c(-z*4.1x+
10)c(0<7.5,45,5>)}}#end B(12,0z*25)B(8y*4<0,12,50>)          // Batronyx ^"^

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I think he was referring to the amount of reflection, as
reflection .4 or even in version 3.5 reflection{.2,.7} would
be something far different from 100% mirror-like reflection...

AFAIK it is not possible to return those, unless you use
trace on objects, of which you have set the reflection inside
an array. A macro could trace the object, check the reflection
in the array, and return intersection point, surface normal, and
reflection value.

Batronyx wrote:

> "Tom Melly" <tom### [at] tomandlucouk> wrote in message
> > IMHO you'd be better of writing macros to handle using cylinders. Any other
> > approach is presumably going to require scattering media (if you want the
> lasers
> > to be visible) and photons (if mirrors are involved), so render times are
> going
> > to shoot through the roof.
> >
> > Now, a nice set of laser-macros that trace a path would be nice - is there a
> way
> > to return the reflection component of a surface?
> >
>
> You could calculate if from the normal returned by trace(). . . but you probably
> already knew that.
>
> Batronyx ^"^
>
> --
> light_source{0,1}#macro c(J,a)sphere{0,1pigment{rgb z}scale a translate J+O}
> #end#macro B(R,V,O)c(0,4)intersection{c(V,R)difference{c(-z*4x+10)c(-z*4.1x+
> 10)c(0<7.5,45,5>)}}#end B(12,0z*25)B(8y*4<0,12,50>)          // Batronyx ^"^

--
Tim Nikias
Homepage: http://www.digitaltwilight.de/no_lights/index.html
Email: Tim### [at] gmxde

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"Tim Nikias" <tim### [at] gmxde> wrote in message
news:3CEC3A25.46062591@gmx.de...
> I think he was referring to the amount of reflection, as
> reflection .4 or even in version 3.5 reflection{.2,.7} would
> be something far different from 100% mirror-like reflection...
>
> AFAIK it is not possible to return those, unless you use
> trace on objects, of which you have set the reflection inside
> an array. A macro could trace the object, check the reflection
> in the array, and return intersection point, surface normal, and
> reflection value.
>

Yeah, that makes more sense upon re-reading. <DOH!> Thanks for setting me
straight.

Let me see if I follow you correctly here; you might not need an array for a
single simple object with an explicit reflection value set in the texture, but
an array would be handy for a union/merge object and/or complex texture mapped
objects right?  If so, how might you get the values for variable reflection,
and/or the interpolated values within a pigment_pattern or image_pattern? The
eval_pigment() function in functions.inc ?

Batronyx ^"^

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