[Pdmtl] [PD] [PD-announce] four more fractal videos, and reposting the two previous ones

jack at rybn.org jack at rybn.org
Ven 4 Fév 11:45:29 EST 2011

> On Fri, 4 Feb 2011, jack at rybn.org wrote:
>>> On Fri, 4 Feb 2011, patko wrote:
>>> Même les polygones concaves sont pas supportés directement par OpenGL
>>> !
>> It is easy to draw a concave polygon with [polygon] in GEM !
> Then why is your patch doing it by gluing many small triangles instead of
> one big 192-sided polygonal contour ?
This is an other method to draw Koch fractal.
In fact, everything depends of the shape of the polygon. In some case it
is possible to draw concave polygon, in other, it is not possible (it is
possible to do it anyway with certain methods).

I didn't mean simply something that
> looks like a concave polygon, I mean a method of building a shape that
> involves drawing a single list of vertices.
> That's because if one tries to make something 192-sided with a single
> [polygon], you write [polygon 192] and you have 193 inlets that have to be
> connected !
With [GEMglVertex3f] you can draw the polygon with dynamic patching.
> Ok, *some* concave polygons are supported by GEM/GL. For example, in
> trianglefan mode, you set a centre, and you put triangle vertices all
> around. This means that the concavities can't go in any direction one
> could want, because in some directions, triangles will overlap areas that
> are meant to not be part of the polygon.
> Concave polygons that can't be drawn so easily, are the one that contains
> no single point from which straight lines to all vertices stay completely
> inside of the polygon. In that case, they have to be broken down in more
> complicated ways.
> Those are difficulties that can be completely avoided by using a plain
> Bresenham rasteriser such as XFillPolygon (from X11) or GridFlow's
> [#draw_polygon] (two distinct implementations of basically the same idea).
>> It is easy to build a Koch fractal with GEM. Open the patch join to this
>> message.
> Yeah, indeed one can use [gemlist].
> Now who wants to make something that looks 3-D with that ? (with
> lights...)
Don't know ! ;)
> (BTW, can you make it so you don't have to copy-paste each time you want a
> new level to the fractal ? because in my patch, I just have to change a
> number)
Sure it is possible with Lua or something else.


>   _______________________________________________________________________
> | Mathieu Bouchard ---- tél: +1.514.383.3801 ---- Villeray, Montréal, QC

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