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Groups > comp.graphics.apps.gnuplot > #3616

Re: Point size default

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Le jeudi 6 avril 2017 06:25:06 UTC+2, Ethan A Merritt a écrit :
> jacques.Lebourlot@obspm.fr wrote:
> 
> > Le lundi 3 avril 2017 13:20:52 UTC+2, Karl Ratzsch a écrit :
> >> Am 03.04.2017 um 10:27 schrieb jacques.Lebourlot@obspm.fr:
> >> > 
> >> > (This was posted on "Gnuplot in Action" forum some time ago, but
> >> > did not get any answer. I need it again...)
> >> > 
> >> > Point sizes are scaled from a "default" size, but I can't find the
> >> > (terminal dependent) absolute value of this default.
> >> > 
> >> > I wish to set a single point (pt 6) in a 3D splot to get a fixed
> >> > circle of (physical) size 1, in the plane of the screen, when I
> >> > change view with the mouse. This is to illustrate 3D coordinate
> >> > systems (see the simplified example below).
> >> > 
> >> > I managed to adjust the size by trial and error (45.5*sc below)),
> >> > but it would be much more convenient to compute the scaling factor
> >> > from known values. Hence, I need the default point size...
> >> > 
> >> 
> >> Point sizes are defined per terminal, and not guaranteed to have a
> >> certain absolute size.
> >> 
> >> You can either plot with style "circles", or put the circle at the
> >> desired position directly via "set object circle".
> >> 
> >>    $zero << EOD
> >>    0
> >>    EOD
> >>    plot $zero us 1:1:(6) with circles
> >> 
> >> or
> >> 
> >>    set object 1 circle at 0,0 size 6
> >> 
> >> hth.
> >> 
> >>  Karl
> > 
> > No! Please check carefully the example given (at the end of my initial
> > message).
> > 
> > * This is a 3D plot (splot), not 2D. hence I cannot use objects.
> > * "6" is not the size, but the "point type" (pt), which is an empty
> > circle * That circle MUST have exacly a physical size of "1.0" => i.e.
> > a radius equal to the unit size of the 3 axes. * It must stay in the
> > plane of the screen when I move the 3D object with the mouse.
> > 
> > I know that sizes are terminal dependent. That is the point of the
> > question... I had to ajust things by trial and errors, by multiplying
> > an "unknown" initial size to get the desired result. That size *has*
> > to be defined (or computed) somewhere in the code, and passed to the
> > graphical engine at some point, but I am not fluent enough in C to
> > find where from the source code.
> > 
> > Thank you for taking the time to answer anyway.
> > 
> > Jacques
> 
> If you are using gnuplot 5, the following may give you some ideas 
> about other ways to create such a plot.
> 
> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
> unset border
> set angles degrees
> set view  equal xyz
> set style data lines
> set zzeroaxis
> set xyplane at 0
> unset xtics
> unset ytics
> unset ztics
> set xrange [ -1.0 : 1.0 ]
> set yrange [ -1.0 : 1.0 ]
> set zrange [ -1.0 : 1.0 ]
> #
> R = 0.3
> set object 1 circle at screen 0.5, 0.5 radius screen R
> #
> splot sample [u=0:360] '+' using (cos(u)):(0):(sin(u)) with lines, \
>              [u=0:360] '+' using (cos(u)):(sin(u)):(0), \
>              [u=0:360] '+' using (0):(cos(u)):(sin(u))
> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
> 
> There is still an issue with scaling the fixed circle radius.
> It may be possible to work out the desired screen fraction 
> dynamically using variables GPVAL_TERM_XMIN, GPVAL_TERM_XMAX, GPVAL_TERM_XSIZE, 
> but I didn't pursue that.  Those are defined for the 2D plot layout,  not 3D, 
> so additional fudge-factors would be needed.
> 
> The development version (gnuplot 5.1) allows you to give the radius in 
> plot or axis coordinates rather than screen coordinates, which may or may not
> make it easier.
> 
>      Ethan

Nice! Thank you. But I still have to find the correct R by trial and error. I will wait for the new version.

Jacques

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Point size default jacques.Lebourlot@obspm.fr - 2017-04-03 01:27 -0700
  Re: Point size default Karl Ratzsch <mail.kfr@gmx.net> - 2017-04-03 13:20 +0200
    Re: Point size default jacques.Lebourlot@obspm.fr - 2017-04-03 06:57 -0700
      Re: Point size default Karl Ratzsch <mail.kfr@gmx.net> - 2017-04-04 06:02 +0200
        Re: Point size default jacques.Lebourlot@obspm.fr - 2017-04-05 09:21 -0700
      Re: Point size default Ethan A Merritt <EAMerritt@gmail.com> - 2017-04-05 21:25 -0700
        Re: Point size default jacques.Lebourlot@obspm.fr - 2017-04-08 05:10 -0700

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