Is there a way to construct a 1-way mirror so that the camera "sees" objects 
through the backside of a mirror that reflects image rays from the object on 
the front side?

Thanks in advance.

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"Catseye" <jpf### [at] comcastnet> wrote:
> Is there a way to construct a 1-way mirror so that the camera "sees" objects
> through the backside of a mirror that reflects image rays from the object on
> the front side?

Hm... that's probably trivial (in the original latin sense, meaning "having
three ways"):

(a) make two copies of your mirror object; make one look like an actual mirror
and apply the no_image keyword, so it is seen in reflections and refractions
but not directly; make the other one look like a window and apply the
no_reflection keyword, so it is seen directly but not in reflections or
refractions

(b) use a plane cut to size with clipped_by (effectively giving you just an
infinitesimal thin square; you can also use two triangles as an alternative),
using a mirror texture and a transparent (or semi-transparent) inside_texture.
(Make sure you get the sides right ;))

(c) ... um... well... okay, maybe it isn't really TRIvial after all :)

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"Catseye" <jpf### [at] comcastnet> schreef in bericht 
news:49642023@news.povray.org...
> Is there a way to construct a 1-way mirror so that the camera "sees" 
> objects through the backside of a mirror that reflects image rays from the 
> object on the front side?
>
> Thanks in advance.
>

Easy. Use interior_texture, like this for example, a mirror box in which you 
can look, so-called Infinity Box. I took this from an old scene of mine:

//--start code--
// for the outside texture of the box, use:
#declare Glass_1 =
      texture {
         pigment {
            color rgbft <1.0, 1.0, 1.0, 1.0, 1.0>
         }
         finish {
            ambient 0
            diffuse 0.0
            phong 0.3
            phong_size 90.0
            reflection 0.0
         }
      }

// for the interior_texture of the box, use this...
#declare Chrome_Metal_3 =
      texture {
         pigment {
            color rgb <0.0, 0.0, 0.0>
         }
         finish {
            ambient 0
            diffuse 0.0
            brilliance 20.0
            phong 1.0
            phong_size 90.0
            specular 1.0
            roughness 0.0004
            reflection 1
         }
      }

 box {
  <-1, -1, -1>, <1, 1, 1>
  texture { Glass_1 }
  interior_texture { Chrome_Metal_3 }
  interior { ior 0.95 }
  hollow
  scale <1.0, 1.0, 1.0>
 }

//--end of code--

In this special case, you would need a light inside the box, but this code 
gives you the idea on how to proceed towards a one-way mirror.

Thomas

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clipka wrote:
> "Catseye" <jpf### [at] comcastnet> wrote:
>> Is there a way to construct a 1-way mirror so that the camera "sees" objects
>> through the backside of a mirror that reflects image rays from the object on
>> the front side?
> 
> Hm... that's probably trivial (in the original latin sense, meaning "having
> three ways"):
>
> <snip>
>
> (c) ... um... well... okay, maybe it isn't really TRIvial after all :)
> 
	Sure is, search the archives for the so-called "vampire" effect
(should be around 1999-2000, *before* povray got no_image,
no_reflection and inside_texture).

		Jerome
- --
mailto:jeb### [at] freefr
http://jeberger.free.fr
Jabber: jeb### [at] jabberfr
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Catseye nous illumina en ce 2009-01-06 22:23 -->
> Is there a way to construct a 1-way mirror so that the camera "sees" objects 
> through the backside of a mirror that reflects image rays from the object on 
> the front side?
> 
> Thanks in advance. 
> 
> 
You can do it the way actual one-way mirrors work.

Have a surface with a relatively low reflection value. The material is similar 
to the lenses of sun glaces. The side where the camera is located is in relative 
darkness. The side facing the mirror have a strong illumination.

The mirror will be constructed similarly to :
difference{
	box{<10,10,1><-10,-10,0>pigment{rgbt 0.5}} // Some darkened "glass"
	box{<11,11,1.1><-11,-11,0.9>pigment{rgbt 1}finish{reflection 0.5}} // The 
mirror part, toward the rest of the scene.
	}
With the camera toward -z.


You still have a reflection of what is on the camera side, but the dark surface 
and the difference in illumination contribute to make it barely noticeable.

-- 
Alain
-------------------------------------------------
'the' is a registered trademark of Microsoft Corporation

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In principle in ray-tracing, you could use one-sided polygons, right?  Right-handed
polygons for one side, left-handed for the other side, of the transmitting/reflecting
surface.

POV doesn't support one-sided polygons, however, I believe.

Dan

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Dan Connelly <djc### [at] yahoocom> wrote:
> In principle in ray-tracing, you could use one-sided polygons, right?  Right-handed
polygons for one side, left-hande
d for the other side, of the transmitting/reflecting surface.
>
> POV doesn't support one-sided polygons, however, I believe.

Well, it supports two-(different)-sided triangles, by specifying both texture{}
and inside_texture{}

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clipka wrote:
> Dan Connelly <djc### [at] yahoocom> wrote:
>> In principle in ray-tracing, you could use one-sided polygons, right?  Right-handed
polygons for one side, left-hande
> d for the other side, of the transmitting/reflecting surface.
>> POV doesn't support one-sided polygons, however, I believe.
> 
> Well, it supports two-(different)-sided triangles, by specifying both texture{}
> and inside_texture{}
> 

This would be a way to do it, then....

Dan

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"Catseye" <jpf### [at] comcastnet> wrote:
> Is there a way to construct a 1-way mirror so that the camera "sees" objects
> through the backside of a mirror that reflects image rays from the object on
> the front side?
>
> Thanks in advance.

plane object, clipped_by box object (not subtraction or union) with texture and
interior_texture.  This gets a rectangular one way mirror, no thickness though.

plane{z,0 clipped_by{box{<-30,-30,-10><30,30,10>}}
  texture{
    pigment{rgbt 1}
    finish{ambient 0 diffuse 0}
  }
  interior_texture{
    pigment{rgb 1}
    finish{ambient 0 diffuse 0 reflection{1}}
  }
}


-tgq

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