Warp wrote:
> Jim Charter <jrc### [at] msncom> wrote:
> 
>>This is done using isosurface's
> 
> 
>   Somehow I have always had a problem with this answer (to the question
> "can I bend an object" or similar). There are several reasons for this.
> 
>   Firstly, and most importantly, the answer is, strictly speaking,
> incorrect. You cannot take any given existing POV-Ray object and somehow
> magically bend it "using isosurfaces". Isosurfaces cannot modify existing
> objects in any way.
>   What you would have to do in order to simulate this is to remodel your
> entire object using isosurface functions. This is not always even
> possible, and in many cases even when possible it's prohibively
> laborious. With some object it doesn't even make any sense, such as
> with meshes.
> 
>   Secondly, it's not the best solution in all cases nor the most efficient.
> For example, if you want to bend a mesh or a heightfield it's usually
> much easier and a lot more efficient to just move the vertex points
> (assuming you have the vertex points and you can change them with
> either POV-SDL or an external program; with heightfields you usually
> can use the heightfield macros in the POV-Ray include library).
>   Sometimes, when bending simple primitives, it's much more efficient
> to model the bent result instead of trying to bend the original
> (typical example: bending a cylinder is better done with a torus
> segment).
> 
>   Thirdly, although this is completely irrelevant and only a question
> of semantics, you are not truely "bending" an isosurface: You are
> creating a new isosurface function which looks like a bent version
> of the original
> 
>   In any case, I think it would be much better to answer like:
>   "One possible solution is to model your object using isosurface
> functions. Isosurfaces can be bent easily."
> 
I think you are being a little extreme.  True, it comes down to the 
semantics of what is meant by "a primitive object in POV", but he seemed 
to indicate that he mostly meant "not triangles".  But I take your point 
that I may think of an isosurface, which happens to define a cube let's 
say, as being more similar to a POV "box" than it actually is.  Also if 
you want to get picky, he never said "bend", he said "warp" or "modify" 
and even specified "using noise or turbulence".  And that is precisely 
what some of Christoff's code does.  So I think it was a reasonable 
answer to the question as asked.  I had also considered mentioning that 
macros have been written which dice and recombine primitives to similate 
a skewed effect, but I didn't want to attempt and exhaustive treatment, 
just answer what he seemed to be asking.

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