[Fluxus] Pdata-Question

[David Griffiths]

Hi Luis,

On Mon, 2010-08-02 at 17:51 +0000, Luis navarro del angel wrote:
> Hi Gabor, 
> 
> Thanks a lot for the corrections in the spiral code, it looks great!!
> 
> I have another question, when I use the pdata-map! I only can make
> work the array type "p" by putting (rndvec). Otherwise if I put only
> numbers in the vector it doesn't do anything. I think I'm missing
> something about the pdata, I already read the pdata and the
> deformation part of the manual, but I can't get it at all.
> 
> I also understand that using pdata-set! we can access to a determined
> vertex, but if we use pdata-map! all the vertices are going to be
> modified, am I right??

That is correct.

> For example, if in this code I replace the "(rndvec)" for a "(vector 1
> 3 0)", nothing happens:
> 
> (clear)
> 
> (define s (build-sphere 10 10))
> 
> (with-primitive s
>       (pdata-map! 
>           (lambda (p)
>                 (rndvec))
>  "p"))

Well, what's happening when you use (vector 1 3 0) is that all the
vertices are collapsing onto that one point, so there is nothing
visible.

If you try using (vadd p (vector 1 3 0)) the sphere should move by that
amount, as it's being added to all the vertices - which is maybe what
you were expecting...

cheers,

dave

> 
> Thanks, 
> 
> Luis