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Ive been trying to make a cone of light that visible, coming from a
flashlight, i really dont know that much yet, ive only had about a month or
so experience with pov-ray. heres the source that im working with, im only
putting the part im having trouble with:
#declare Light_Cone =
cone { <0,1.928,0>, .182
<0,25,0>, 2.5
texture { pigment { White }
finish { ambient 6 }
}
}
light_source {
<0,1.928,0>
color White
spotlight
point_at <0,25,-20>
radius .182
falloff 5.725
looks_like { object { Light_Cone } }
}
the problem is that it doesnt show up at all in rendering. i know thats not
a very much help, but i would appreciate any ideas any one has. thanx!
~Nick~
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"Nick Holcomb" <enr### [at] PunkAss com> wrote :
>
> the problem is that it doesnt show up at all in rendering. i know thats
not
> a very much help, but i would appreciate any ideas any one has. thanx!
Where is your camera? Does it look at the cone?
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Your cone isn't pointint at the right position.
While your spotlight points at <0,25,-20>, your
cone just points to <0,25,0>. Looks_like doesn't
rotate objects, it just uses them as defined.
And perhaps scaling isn't right, though I'm not
sure without a look at your scene. The cone's
end is only 2.5, but perhaps that is wanted...
Nick Holcomb had this problem:
> #declare Light_Cone =
> cone { <0,1.928,0>, .182
> <0,25,0>, 2.5
> texture { pigment { White }
> finish { ambient 6 }
> }
> }
>
> light_source {
> <0,1.928,0>
> color White
> spotlight
> point_at <0,25,-20>
> radius .182
> falloff 5.725
> looks_like { object { Light_Cone } }
> }
>
--
Tim Nikias
Homepage: http://www.digitaltwilight.de/no_lights/index.html
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You have the cone surface intersecting the light source
cone { <0,1.928,0>, .182
light_source { <0,1.928,0>
It may help if you move the light or end the of the cone just a little.
I found that if a plane intersects a light source some strange things can
happen. Sometimes little black artifacts sometimes it acts like there no light
at all.
--
Have Fun!
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In article <3CA2CAA6.20C1614C@joplin.com>,
Leroy Whetstone <lrw### [at] joplincom> wrote:
> I found that if a plane intersects a light source some strange things can
> happen. Sometimes little black artifacts sometimes it acts like there no light
> at all.
This is just another case of the coincident surface problem...POV
doesn't know which side of the surface the light is on, so it
unpredictably gets shadowed by it depending on how the precision errors
work out.
--
Christopher James Huff <chr### [at] maccom>
POV-Ray TAG e-mail: chr### [at] tagpovrayorg
TAG web site: http://tag.povray.org/
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Christopher James Huff wrote:
> This is just another case of the coincident surface problem...POV
> doesn't know which side of the surface the light is on, so it
> unpredictably gets shadowed by it depending on how the precision errors
> work out.
Why not assume it's on both sides? Or neither...
--
Tim Cook
http://empyrean.scifi-fantasy.com
-----BEGIN GEEK CODE BLOCK-----
Version: 3.12
GFA dpu- s: a?-- C++(++++) U P? L E--- W++(+++)>$
N++ o? K- w(+) O? M-(--) V? PS+(+++) PE(--) Y(--)
PGP-(--) t* 5++>+++++ X+ R* tv+ b++(+++) DI
D++(---) G(++) e*>++ h+ !r--- !y--
------END GEEK CODE BLOCK------
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That's the typical coincidence surface problem:
POV-Ray has no means of checking if two
objects actually have coincident surfaces. It just
happens to hit one or the other by random.
This is also true for internal calculations of light,
I guess.
"Timothy R. Cook" wrote:
> Why not assume it's on both sides? Or neither...
--
Tim Nikias
Homepage: http://www.digitaltwilight.de/no_lights/index.html
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In article <3CA3AA9A.D891977D@scifi-fantasy.com>,
"Timothy R. Cook" <tim### [at] scifi-fantasycom> wrote:
> Christopher James Huff wrote:
> > This is just another case of the coincident surface problem...POV
> > doesn't know which side of the surface the light is on, so it
> > unpredictably gets shadowed by it depending on how the precision errors
> > work out.
>
> Why not assume it's on both sides? Or neither...
Because then you would never get any shadows. ;-)
POV doesn't know the light is "on" the surface, so it can't just avoid
that surface. If you made the surface shadowless, the problem would go
away, but that has other obvious problems.
--
Christopher James Huff <chr### [at] maccom>
POV-Ray TAG e-mail: chr### [at] tagpovrayorg
TAG web site: http://tag.povray.org/
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Christopher James Huff wrote:
> POV doesn't know the light is "on" the surface, so it can't just
> avoid that surface.
But the light (if we're talking about a point light) is a known
single point! It's easy to test if it's on the surface!
--
Tim Cook
http://empyrean.scifi-fantasy.com
-----BEGIN GEEK CODE BLOCK-----
Version: 3.12
GFA dpu- s: a?-- C++(++++) U P? L E--- W++(+++)>$
N++ o? K- w(+) O? M-(--) V? PS+(+++) PE(--) Y(--)
PGP-(--) t* 5++>+++++ X+ R* tv+ b++(+++) DI
D++(---) G(++) e*>++ h+ !r--- !y--
------END GEEK CODE BLOCK------
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In article <3CA3D327.77480C19@scifi-fantasy.com>,
"Timothy R. Cook" <tim### [at] scifi-fantasycom> wrote:
> But the light (if we're talking about a point light) is a known
> single point! It's easy to test if it's on the surface!
POV would have to check that point against the bounding box of every
object in the scene, and then against the surface of any objects it
might be on. This would slow things down noticeably, just to handle what
is really a degenerate case.
And then, the correct thing to do would be to always consider the light
shadowed by the object, otherwise you will get wrong shadows with
objects like a torus, where other parts of the object should cast
shadows from a point just above the surface. Of course, this wouldn't be
very useful...it would just slow things as mentioned above, and replace
user complaints about lights not lighting properly with complaints about
lights not lighting at all.
You could also mess around slightly with the depth values, basically
have POV lie to itself it doesn't "see" intersections that are very
close to the light source. The point is this just isn't necessary...just
don't put your lights on a surface! That situation never occurs in
reality and there is no reason to bother handling it.
--
Christopher James Huff <chr### [at] maccom>
POV-Ray TAG e-mail: chr### [at] tagpovrayorg
TAG web site: http://tag.povray.org/
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