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I haven't seen anyone mention negative light sources. Or maybe I'm the only
one that thinks it's really cool. I haven't thought of a practical use of
this, aside from looking weird, but I'm sure you could do something with it.
camera {location <0, 5, 5> look_at <0, 0, 0>}
light_source {500, 1}
light_source {<-500, 500, 500>, 1}
light_source {<0, 500, -500>, -1}
sphere {0, 1 translate <0, 1, 0> pigment {rgb 1}}
cylinder {0, <0, -1, 0>, 30 pigment {rgb 1}}
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"Ben Lauritzen" <loo### [at] yahoo com> wrote in message
news:3a690da4@news.povray.org...
> I haven't seen anyone mention negative light sources. Or maybe I'm the only
> one that thinks it's really cool. I haven't thought of a practical use of
> this
Yep, some people know of it anyway, it's just not written up in the
documentation I guess.
I put it to use for making light beams with varied concentric intensity.
Another way of doing so would have been to use caustics made from a spotlight
shining through a clear refractive lens with a onion normal, for example.
Can also darken places of a room for effect. So there are "practical" uses.
Bob H.
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Ben Lauritzen wrote:
> I haven't seen anyone mention negative light sources. Or maybe I'm the only
> one that thinks it's really cool. I haven't thought of a practical use of
> this, aside from looking weird, but I'm sure you could do something with it.
>
> camera {location <0, 5, 5> look_at <0, 0, 0>}
> light_source {500, 1}
> light_source {<-500, 500, 500>, 1}
> light_source {<0, 500, -500>, -1}
> sphere {0, 1 translate <0, 1, 0> pigment {rgb 1}}
> cylinder {0, <0, -1, 0>, 30 pigment {rgb 1}}
>
> [Image]
Hadn't though to try a negative light source yet. I like it.
You can do really cool effects with unusual lighting. The camera here is
looking at a white plane, all of the patterns are the result of shadows from an
object not in the frame. Is there anyway to make the camera not see certain
objects, so that they affect the scene without being seen? Sorta how the camera
doesn't see a light source.
Dan
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how strange, I just read something about this the other day!
(http://povplace.addr.com/tips/lighting.htm)
Steve
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"Dan Johnson" <zap### [at] hotmail com> wrote in message
news:3A69598E.602102D3@hotmail.com...
>
> Hadn't though to try a negative light source yet. I like it.
>
> You can do really cool effects with unusual lighting.
> Is there anyway to make the camera not see certain
> objects, so that they affect the scene without being seen? Sorta how the
camera
> doesn't see a light source.
It helps when you have a nice effect scene like this.
Yes, you can use MegaPov to do so anyway, by applying the 'no_image' keyword to
your object(s).
Bob H.
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In article <3a693c10$1@news.povray.org>, "Bob H."
<per### [at] aol com?subject=PoV-News:%20&body=Relating%20to%20POV-Ra
y:> wrote:
> Yep, some people know of it anyway, it's just not written up in the
> documentation I guess.
It is mentioned indirectly...the docs refer to the fact that you can
specify negative values in colors, but I didn't see any specific
mentions of negative light sources...which is strange, because I'm sure
I saw them mentioned in there before.
--
Christopher James Huff
Personal: chr### [at] mac com, http://homepage.mac.com/chrishuff/
TAG: chr### [at] tag povray org, http://tag.povray.org/
<><
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Just playing.
#version unofficial MegaPov 0.6;
camera {location 100 look_at 0}
$seed1=seed(1305987);
$A=0;
#while (A < 30)
$A=A+1;
light_source {
<100*rand(seed1)-50,100*rand(seed1),100*rand(seed1)-50>,
<2*rand(seed1)-1,2*rand(seed1)-1,2*rand(seed1)-1>
spotlight
point_at <100*rand(seed1)-50,-100*rand(seed1),100*rand(seed1)-50>
radius 90*rand(seed1)
falloff 90*rand(seed1)}
cylinder {
$pos1=<100*rand(seed1)-50,30*rand(seed1),100*rand(seed1)-50>;
pos1,
<pos1.x,pos1.y+40*rand(seed1),pos1.z>,
5*rand(seed1)
pigment{rgb<2*rand(seed1)-1,2*rand(seed1)-1,2*rand(seed1)-1>}
no_image
}
#end
cylinder{0,y*-1,300 pigment{rgb 1}}
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In article <3a69c4ba@news.povray.org>, "Ben Lauritzen"
<loo### [at] yahoo com> wrote:
> Just playing.
Hmm, I wonder what this would look like if you put it inside a plain
white sphere with double_illuminate...
--
Christopher James Huff
Personal: chr### [at] mac com, http://homepage.mac.com/chrishuff/
TAG: chr### [at] tag povray org, http://tag.povray.org/
<><
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"Dan Johnson" <zap### [at] hotmail com> wrote in message
news:3A69598E.602102D3@hotmail.com...
<snip>
> Is there anyway to make the camera not see certain
> objects, so that they affect the scene without being seen? Sorta how the
camera
> doesn't see a light source.
>
> Dan
>
I think that if you make an object's bounding box not surround the object,
then it will not show up in the image. For that object to have shadows, you
need to have the bounding box in between the object and the light. but not
in between the camera and the light.
I remember a long time ago people doing "vampire" objects (which do not have
an image in a mirror) by this method.
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> Hmm, I wonder what this would look like if you put it inside a plain
> white sphere with double_illuminate...
Quite ugly actually, but that's my opinion.
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