"marabou" <not### [at] availableyet> wrote in message news:3bfbf8ed@news.povray.org...
>
> hello,
> i made a shape with bicubic_patch and failed as i tried to difference it
> from a box:
>
> difference{
> box{<0,0,0>,<1,1,1> pigment{color Green}}
> object{
>         a_bicubic_object
> }
> }//difference
>
> the result was an empty scene.
> is there any way to come by this problem?

As warp explained, this won't work directly. However, heightfields _do_
difference correctly. Depending on what you want to do, this will work: render
an orthographic view of your patch object, with the cutting side pointing
towards the camera, and a black to white gradient assigned to the patch -- back
to front with respect to the camera view -- and use ambient one and no lights.
Use the resulting image as a heigtfield and difference it from the cube. In 3.5
or MegaPOV, using max_extents on your patch object can help you get the proper
scaling values for the heightfield.

Hope that helps :)

Batronyx ^"^

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