"scott" <sco### [at] scottcom> wrote in message news:48e34c55@news.povray.org...
>>  Their problem is that automatically creating rounded corners for any
>> given object:
>>
>> 1) is impossible in the general case,
>> 2) in many cases where it's possible it results in extremely slow 
>> renders,
>
> Those first two are not really problems though - ie we shouldn't say not 
> to include a feature because it won't work with all possible objects and 
> might result in extremely slow renders sometimes.
>
>> 3) would require tesselating the object and rendering the resulting mesh
>>   (with the corner modifications).
>
> That's not the only way to do it.
>
>>  POV-Ray, however, handles mathematical primitives (such as boxes and
>> planes) and their CSG. Rounding their corners is a problem which is
>> several orders of magnitude harder.
>
> But not impossible, look at any CAD software that manages it with 
> mathematically defined CSG.  The problem I see with POV, is how to specify 
> which edges you want to be rounded, so far we have no way of specifying 
> edges in the SDL.
>
> I have no idea how CSG objects are stored internally in CAD software, but 
> at each stage of the CSG you can somehow specify edges and faces etc to 
> apply rounds and chamfers to.  I don't know how you would attempt to 
> replicate this in a text-based way.
>
> Internally, the POV engine would need to see what faces were connected to 
> the specified edge, and remove/generate the correct geometry to round that 
> edge.

The main problem, scott, is that POV generally doesn't work with 
faces/surfaces. It works in solids.

As far as I can see, the only generalisable methods of doing this are:
    1) Use CSG to break up the intersection into parts and build the rounded 
bits by hand or
    2) Create an isosurface that closely follws the outline of the CSG 
objects but smooths it out.

I beleive there are attempts at both in the POV object library.

Rarius

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