Thanks for the solution below. It worked rather nicely. While we are
on the filling regions topic, another feature that would be nice to
have is shading/coloring the entire section of a solid. For example,
we rotate the region discussed below about the y-axis, and then we
want to plot the solid of rotation together with a cross section (say
the disk defined by 0.5<=y<=0.6). Using parametric_surface, with a
color different from one used for the solid, does a pretty good job,
but being able to do what I just proposed would be an enhancement, I
think.
Milan
* Mario Rodriguez <biomates at telefonica.net> [2007-08-26 13:33:03 +0200]:
> Milan Lukic escribi?:
> > I have had a lot of fun drawing some regions and surfaces using the
> > Draw package. Thank you Mario for the great work.
> >
> > I encountered a small problem in trying to plot the region bounded by
> > x=y-y^2 and the y-axis. Namely, implicit(x=y-y^2,x,0,1/4,y,0,1)
> > results in a Lisp error, while replacing 1/4 by 0.25 works fine.
> >
>
> This is a work-around for your particular problem, but not a general
> solution:
>
> pairs: makelist((u:t/50.0,[u-u^2,u]),t,0,50)$
> draw2d(polygon(pairs))$
>
> See also options `transparent', `fill_color', `border', `line_width',
> `line_type' and `color' to fit specific needs.
>
>
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