filling out contours - Graphics

benner <gothic13@gmx.de> wrote:
> Hi there, I´m plotting 3D data ( just viewing the bottom from above ).
> I´ve been using pm3d for colours, but now I´d like gnuplot to have an
> exact border for the colours, not one fading into another. If I do so
> with pm3d, the trouble is, it looks terrible as one can see every
> single pixel.

While that may be so, the alternative would be a lie. The disply
would be claiming a precision of your plotted data that simply doesn't
exist. Please keep in mind that this is a scientific plotting
program. Prettiness is thus secondary to honesty.

--
Hans-Bernhard Broeker (broeker@physik.rwth-aachen.de)
Even if all the snow were burnt, ashes would remain.

> exact border for the colours, not one fading into another. If I do so
> with pm3d, the trouble is, it looks terrible as one can see every
> single pixel. I can´t afford putting dgrid3d above 150,150,2 as I have
> to plot about 400 different files, so it´s a matter of time. My idea
> was, to use the normal contour function and it works well, the only
> trouble is, I can just draw lines and stuff. Is there any way to fill
> in some colours between the lines, as that would be exactly what I

Prepare contours in an external application and draw them by "with
filledcurves".

There is an undocumented switch "set pm3d at C" for filling contours, but it
does not work properly, because gnuplot does not "close" contours around
graph boundaries.


> "humankind built the a-bomb. would a mouse ever build a mouse trap?"

mice are studying people :-))

Thanks Petr, despite the problems with "pm3d at C", it should work for
my particular problem.
@ Hans-Bernhard Broeker: I´m writing a comparison of gnuplot and its
commercial brother Tecplot, which can do what I asked for so I was just
wondering whether gnuplot can do the same. I don´t see the difference
between drawing contours simply as lines on the one hand and filling
out the space between the lines on the other hand, as long as one
remembers that e.g. "red" doesn´t mean 0.758 but any value between 0.7
ans 0.8. Maybe we just misunderstood each other or I didn´t express
myself properly. Anyway, don´t want to start a flame war here =)

> I don´t see the difference between drawing contours simply as lines on the
> one hand and filling out the space between the lines on the other hand

A (contour) line must be closed in order to be filled.

In the current gnuplot contour generator, if a contour hits graph boundary,
then it does not close this curve around respective corners of the graph
boundary. Therefore you can see crazy shapes "pm3d at C" for those contours.
Fixing this should be nice ...

---
PM

Well, I see your point. Reminds of drawing pictures in paint, trying to
fill out a certain figure and suddenly the whole screen turns black =)
I´ve been working with this pm3d at C during the day. I´ve had some
trouble with it, but basically it worked, probably cause I only have
one contour to be filled.
Thanks again for your help. By the way, how do you know this if it´s
undocumented?
I´d really like to fix this as to me it´s a big advantage for
gnuplot, but I´m just not able to do so.
Regards
benner

"humandkind built the a-bomb. would a mouse ever build a mouse trap?"

> By the way, how do you know this if it´s undocumented?

Sorry, it is documented, but only in the source code :-))
(Yes, I wrote it there.)

---
PM

benner <gothic13@gmx.de> wrote:

> By the way, how do you know this if it´s undocumented?

Well, sometimes it does help if the people manning the "help desk"
actually know what they're talking about, see? You're talking to
people who have the source code within arm's reach and work on it on a
regular basis. We don't need to read documentation --- we write it.

--
Hans-Bernhard Broeker (broeker@physik.rwth-aachen.de)
Even if all the snow were burnt, ashes would remain.