Hi,
i have a problem with two objects, one of these is transparent (object 1),
the other is not (object 2).
when i look through object 1 i can also look through object 2.
and see the background, which should be invisible.

(camera )------------> (object1) ---------> (object2) ----->(background)

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Uwe Lohrey wrote:

> Hi,
> i have a problem with two objects, one of these is transparent (object 1),
> the other is not (object 2).
> when i look through object 1 i can also look through object 2.
> and see the background, which should be invisible.
>
> (camera )------------> (object1) ---------> (object2) ----->(background)

The following is presuming, since you didn't provide much
info, that you have a plane beneath object 1 and 2. If you don't
I, we, would need more info to help you adequately.

  What is happening here I believe is when you have the camera
close to the same level as the horizon, both front and rear,
and you are looking at an object, also located near the plane,
you see a reflection of the horizon behind the camera, being
reflected off the objects in the scene.
  It becomes really pronounced when highly reflective surfaces
are being used. In your case you are seeing the light
reflected off of object #2 and passing back through #1 to the
camera

Render the following for an illustrated example:

camera{location<0,  1, -10>look_at y*1}
light_source{  <0, 10,-500>rgb 1}
light_source{  <0,500,   0>rgb 1}

plane{y,0 pigment{rgb .75}}

sphere {<0,1,0>,1
pigment{rgb 1}
finish {ambient .2 diffuse 0 reflection 1}}


  The above illustrates how the camera picks
up the reflected image of the horizons edge
almost precisely at the level where the distant
horizon visually intersects the the object in
line of sight.
    Try one time changing the look_at, to point up
a little bit, or just place a vertical plane
somewhere behind the camera's location and see
if it goes away.

If this is not the scenario more input is needed from you.

Ken

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