In article <3caa034f@news.povray.org>,
 "Patrick Dugan" <pat### [at] usnetcomcorpcom> wrote:

> #declare One =
> difference {
>    height_field {
>       tga "MyPicture.tga"
>       smooth
>       hierarchy on
>       translate <-0.5, -0.5, -0.5>
>       rotate <-90,0,0>
>       scale <0.3,1,0.1>
>       photons {target reflection on}
>    }
>    box{<-0.2,-0.6,-0.02>,<0.2,0.6,2> pigment {rgbft <1,1,1,0,1>}
>       no_shadow no_reflection no_image photons {collect off}
>    }
>     bounded_by { box{<-5,-5,-5>,<5,5,5>}}
> }

A point is considered "inside" a height_field if it is "below" it. If 
the height_field is not rotated or sheared, all points -y of some part 
of the surface are inside it.

POV seems to have a hard time with this fact in this case, it knows the 
height field isn't bound to a cubic space and that the difference 
surface may occur anywhere, so it considers it to be infinite when 
computing the bounding boxes. A better solution might be to use a box 
extending very far downward for the CSG bounding computations, or to 
limit the height_field object to a cube.

-- 
Christopher James Huff <chr### [at] maccom>
POV-Ray TAG e-mail: chr### [at] tagpovrayorg
TAG web site: http://tag.povray.org/

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