Alain Martel <kua### [at] videotronca> wrote:

> > The attached image shows two renderings of the same scene.  The right image is
> > the same as the left, except that I added a completely transparent box, whose
> > purpose was to support media with some ground fog:
> >
> > box {
> >     -size/2, size/2
> >     texture { pigment { color rgbt 1 } }
> >     translate <0, size.y/2, 0>
> > }
> >
> > As you can see, the box shows up as a mirror instead of being transparent.
> >
> > The scene is fairly complex, but here are a few details that might help point
> > out to the experts what the problem might be:
> >
> > 1.  The whole scene is inside of a mesh-based sky sphere, but I verified that
> > the problem shows up even if that is turned off.
> > 2.  I have enabled radiosity, but I verified that the problem shows up without
> > it as well.
> > 3.  The light source is a sun emulator using a parallel area_light at a far
> > distance from the scene
> >
> > I also tried using rgbf 1.0 as the pigment for the box, but I get the same
> > problem.
> >
> > Any ideas?  It's driving me crazy
> >
> > -- Chris R.
>
> That looks like it could be a coincident surface issue.
> Try placing the box slightly lower so that it's bottom face is just
> under the ground or slightly higher so that it don't touch the ground.
> Some options :
> box {
>     -size/2-0.1*y, size/2 // lower
>     texture { pigment { color rgbt 1 } }
>     translate <0, size.y/2, 0>
> }
>
> box {
>     -size/2+0.1*y, size/2 //higher
>     texture { pigment { color rgbt 1 } }
>     translate <0, size.y/2, 0>
> }
>
> box {
>     -size/2, size/2
>     texture { pigment { color rgbt 1 } }
>     translate <0, size.y/2-0.1, 0> // lower
> }
>
> box {
>     -size/2, size/2
>     texture { pigment { color rgbt 1 } }
>     translate <0, size.y/2+0.1, 0> //higher
> }

Thanks, I thought about that too, but I simplified the scene to the point where
there were no more coincident surfaces and it still happened.

-- Chris R.

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