"Neil Kolban" <kol### [at] kolbancom> wrote in message 
news:42002dbf$1@news.povray.org...
> Folks,
> I wanted to subtract from an object an "indentation" of a complex shape. 
> Reading about CSGs and difference, it clearly stated that only solid 
> objects that have clearly defined insides and outsides could be used. 
> Looking at the manual, it seems to say that height_fields are solid 
> objects.
>
> Can anyone confirm or deny that a height_field can be used as an object 
> that I can remove from another using a CSG difference?
>

I have had really bizarre things happen when I have tried to use 
heightfields to subtract from a CSG object.  I had a very simple 
heightfield, which was simply a white circle with a black background.  I 
tried differencing it from a CSG box.  One of the bizarre effects was that 
no matter what I did, the hole cut by the heightfield would extend all the 
way through to the other side of the object.  It didn't seem to matter how 
small I made the heightfield or how deep I made the box.

Using the following code, it's pretty easy to demonstrate the problem. 
Hole.png is simply a white circle on a black background.  The same thing 
appears to happen under 3.5, 3.6.1, and MegaPov 1.1.

//replace the "basic scene" sphere with this
difference {
  box { 0, 1 pigment {Red} }
  height_field {
    png "hole.png"
    rotate x*-90
    scale 0.5
  }
  rotate y*180
}

-- 
Jeremy
www.beantoad.com

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