[Fluxus] pdata size behavior

[Glauber Alex Dias Prado]

Dave Griffiths <dave at pawfal.org> writes:

> btw - I didn't check that script for non-square dimensions, so probably
> some w's and h's will need flipping.

i will use only squared i think, at least for the moment :).

>
> cheers,
>
> dave
>
> On Tue, 2010-05-25 at 12:13 +0300, Dave Griffiths wrote:
>> Hi Glauber,
>> 
>> This is due to the fact that (build-seg-plane) returns a primitive which
>> is an un-indexed quad list - the vertices are not shared between the
>> faces.
>> 
>> The best way to deal with this is to make an indexed polygon object
>> yourself with build-polygons, and stitch the vertices together with the
>> index - for example:
>> 
>> (define (build-mesh-plane w h)
>>     (let ((p (build-polygons (* w h) 'quad-list)))
>>         (with-primitive p
>>             (pdata-index-map!
>>                 (lambda (i p)
>>                     (vector (modulo i w) (quotient i w) 0))
>>                 "p")            
>>             (poly-set-index     
>>                 (build-list
>>                     (* (- w 1) (- h 1) 4)
>>                     (lambda (i)
>>                         (let ((f (+ (quotient i (* 4 (- w 1))) (quotient i 4))))
>>                             (list-ref (list f (+ f 1) (+ f w 1) (+ f w))
>>                                 (modulo i 4))))))
>>             (recalc-normals 1)) p))
>>

wow, thank you :).

>> 
>> (clear)
>> (hint-wire)
>> (wire-colour 0)
>> (define p (build-mesh-plane 10 10))
>> 
>> (with-primitive p
>>     (pdata-map!
>>         (lambda (p)
>>             (vadd p (vmul (srndvec) 0.2)))
>>         "p")            
>>         (recalc-normals 1))
>> 
>> On Mon, 2010-05-24 at 19:41 -0300, Glauber Alex Dias Prado wrote:
>> > Hey ppl,
>> > 
>> > I was figuring out how to make a kohonen map
>> > <http://en.wikipedia.org/wiki/Kohonen_map> using pdata to represent my
>> > err data, but this is a bit tricky as there are much more pdata than
>> > vertices, and preferably i would like a one-to-one mapping:
>> > 
>> > (clear)
>> > (hint-none)
>> > (hint-wire)
>> > (point-width 4)
>> > (hint-points)
>> > ;(translate (vector 0 0 9))
>> > 
>> > (define grid
>> >     (build-seg-plane 10 10))
>> > 
>> > above is just the grid which i would like to manipulate as if it were a
>> > matrix of vertices, but:
>> > 
>> > (with-primitive grid
>> > 	(pdata-size))
>> > returns 400
>> > 
>> > and i would like something like 100 at least for vertex position
>> > manipulation, so is those 400 related to all (t p n c) pdatas and there
>> > are only 100 for "p"?
>> > 
>> > I guess not, so i might be using the wrong primitive type for this
>> > maybe?
>> > 
>> > does someone know what kind of primitive i could have a
>> > one-vertex-per-pdata representation? 
>> 
>>