[PD] Vertex transformations

Stefan Turner stefan_turner at yahoo.co.uk
Wed Mar 31 15:52:57 CEST 2004


Thanks for the reply. If it's of any use, an idea I
had for transforming vertex positions and colours is
just something like:

 | [1.2\ [3.4\
 |  |     |
[transform-vertex $fx $fy+$f1 $fz*$f2]
[model whatever.obj]

where 'transform-vertex' takes any number of floats
referenced $f1, $f2...etc (like expr: apologies if I
got the syntax wrong, I don't have pd on this
computer) and has $fx,$fy,$fz for the current vertex
coords. The example above would therefore shift by 1.2
in the y axis and scale by 3.4 in the z axis. A
similar thing could be done with colours. I think even
though this is quite simple it would do for many

This could be more useful in conjunction with a
'gem-moses' which would act as two 'separators', the
relevant one being chosen depending upon the vertex
position, or something along these lines. (I am not
sure if this would work as I know nothing about how
Gem builds the rendering network etc.)

I would try to code these myself but I don't think I
am up to doing externals yet... Anyway these are just 
ideas and I'm sure you have something similar going
on. Good luck and make sure you tell us all when
you've got something!


 --- chris clepper <cgc at humboldtblvd.com> wrote: > On
Mar 30, 2004, at 8:36 AM, Stefan Turner wrote:
> > Hey,
> >
> > Any chance of some more info on how this might
> work?
> > Would there be a new object to apply any
> > transformation to vertex positions and colours, or
> > would it be based on getting and setting arrays? I
> > think both could be quite useful, with the
> > 'transform-vertex' (or whatever) object being
> > (presumably) more efficient and ok for simpler
> stuff,
> > and arrays for anything more complicated.
> Nothing about vertex arrays is set at this point. 
> Right now it's just 
> a collection of objects on my HD that I'm trying to
> make into a 
> coherent set of tools for 'dynamic geometry'.  The
> current idea is to 
> have a set of vertex generators like a grid or a
> .obj model loader and 
> a set of vertex manipulators for color, position and
> so on.  The idea 
> is to process vertex, color, normal and texture
> coordinate data just 
> like pixels or audio.  Pd/GEM is not a very
> effective environment for 
> representing large data sets to the user, so very
> fine editing of the 
> data might not be all that possible.  The goal is to
> have a way to 
> algorithmically alter geometry over time - think
> about something like 
> newwave or Cyrille's pmpd applied any model you load
> into GEM and you 
> start to get the idea.  There will probably be lots
> and lots of of 
> problems to solve before these objects become all
> that useful.
> > Sorry for all the questions, but this sounds just
> like
> > what GEM is currently lacking (for my needs).
> Sorry if
> > any of this has been answered: I haven't been able
> to
> > find much about it.
> By all means let us know what you find lacking about
> GEM.  The past 
> year has been spent getting 'the basics' on each
> platform up to par and 
> improving performance and stability.  Now it's time
> to get some really 
> interesting things going.
> cgc
> > Cheers,
> > Stefan
> >

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