Re: polygon issues

[Manfred S. <man...@gm...>]

Am Mittwoch, den 15.10.2008, 12:27 -0700 schrieb Ethan Merritt:
> On Wednesday 15 October 2008 08:05:26 Manfred Schwarb wrote:
> > Hi,
> > 
> > I'm experimenting with the new polygon object and encountered two stumbling blocks.
> > 
> > 1) I'm doing something like
> >      set object 1 polygon \
> >   from screen 0.820186699373,0.915943621944 \
> >      to screen 0.816522727098,0.922822961096 \
> >      to screen 0.824158694467,0.917927083652 \
> >      to screen 0.820186699373,0.915943621944 front fc ls 3 fs solid 1.0
> > 
> >   and I get "Polygon is not closed - adding extra vertex", although my polygon is 
> >   perfectly closed?
> 
> For what it's worth, I don't get that warning message when I cut-and-paste your
> above commands. Maybe it's due to rounding error when storing floating point numbers?
> But that warning should not harm anything.
> 

I didn't try it separately, but in a gnuplot script sketched as follows
  set term png truecolor
  set multiplot
  set pm3d interpolate 40,40 explicit map
  set object 1 polygon ...
  splot ... with pm3d
  ...
I got these warnings.

It's on a x86_64 box, this may be the difference (I vaguely remember
there is some excess precision on x68_32 [-mfpmath=387] or so).
For me it was just irritating, I checked the numbers at least twice and
could not find a typo ..

But in any case, I think for
  set object 1 polygon from x1,y1 to x2,y2
i.e. drawing a simple line, this message should be suppressed.

> > 2) clipping:
> >   At the plot borders, these objects seem to be clipped (cut off). As I use these objects as 
> >   somehow generic drawing objects in a mixture with "set arrow", things become 
> >   really messy, as arrows are not clipped.
> >   What I would need are objects that are not clipped, so I can use the whole screen.
> >   Up to now I found no way to deactivate this clipping feature. Is there a way to do so?
> 
> Heh.  You have no idea how much time I spent to get that clipping to work.
> 

Hmm :-) I guess doing this clipping is a reasonable default and what
most people probably expect.

> But yes, I can imagine there are cases when clipping is undesirable.
> The question is: is that a property of the object or a property of the whole plot?
> I'll have to think about it.
> 
> Which would be more obvious in your case?
>    set clip <something>
>    plot 'foo'
> or
>    set object 1 polygon noclip ....
>    plot 'foo'
> 

The meaning of "set clip" is already complicated enough, IMHO.
So I would be in favor of the noclip argument to "set object".

But either thing would be great.

Thanks!
Manfred