By golly, they *are* holes. How strange. Because they're (a) the holes that
should be there, plus (b) holes that exactly mimic where i see other parts
of the isosurface when the plane is not cut out from it. (try rendering the
scene without the plane, and remember where peices of the isosurface are,
and then rerender the scene with the plane cut out, and you'll see that the
places where the peices used to be but aren't are now holes in other parts
of the isosurface hit by the same ray.)

Looking at it from the opposite side, however, doesn't show the extra holes
that I explained in (b). set background{rgb 1} and change the camera
location from <0,0,-15> to <0,0,15> and you'll see that those holes
disappear. If you then set the plane's normal from <1,1,-.5> to <1,1,.5>,
you'll see that new holes have been cut out on the side that we were
originally looking at.

I still think there's something strange here. I can render some images if
need be.

- Slime
[ http://www.teja.nu/slime/ ]
[ http://www.teja.nu/slime/images/ ]

"Mike Williams" <mik### [at] nospamplease> wrote in message
news:yrU33AA5+pr7### [at] econymdemoncouk...
> Wasn't it Slime who wrote:
>
> >The isosurface in this scene has a plane cut out from it. The light
source
> >is at the same location as the camera, so no shadows should be visible.
> >However, the isosurface seems to be showing shadows from the part of it
that
> >has been off by the plane.
>
> They're not shadows, they're holes. You're looking through the holes and
> seeing the background. They happen to look black in this scene because
> your background is black.
>
> (1) Add "background {rgb <0,0,1>}" and almost all the "shadows"
> disappear.
>
> (2) Add "max_gradient 3" and the few remaining "shadows" also disappear.
> I recommend explicitly setting a sensible max_gradient for all 3.5
> isosurfaces.
>
> (3) Add "max_trace 3" to render the whole of the surface. Max_trace is
> required for all CSG operations involving isosurfaces.
>
> --
> Mike Williams
> Gentleman of Leisure

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