Re: please try POV-Ray and VRML terminals (Re: Now working on POV-Ray terminal)

[V. <gae...@en...>]

  Hello,

  Great to see a gnuplot output some povray. It fantastic.

  I gave it a quick look, but I won't have time to look at it again this
week.

#### My first impressions :

  No colours, and color-box, that's really sad. I guess it is just a
matter of giving it a bit more work.

  Titles should be reasonably easy to add.

  set pm3d hidden3d doesn't seem to work.

  The conventions you used to specify surface type are not quite
intuitive. There probably will be some thinking to do as to what gnuplot
instructions generate what povray material.

  I suggest trying to stick as much as possible to gnuplot standard
behaviour :

  ***  No options -> wireframe + some thing like this :
pigment {
                gradient z
                 color_map {
                [0.0  color rgb <0,0,0>]
                [0.25 color rgb <0.5,0,1>]
                [0.5  color rgb <1,0,0>]
                [0.75 color rgb <1,0.5,0>]
                [1.0  color rgb <1,1,0>]

    (of course the value of the colour map would be generated from the
gnuplot palette, possibly using gnuplot's "show palette palette <n>"
function)

  *** set p3md transparent -> only wireframe (current default behaviour).

  *** unset surface would turn the wireframe off.

#### A few comments on the code

  Looking at gnuplot's code and at the way you patched gnuplot to have
the povray terminal work, this patch seems a bit of a dirty hack. It
establishes special routines to plot vrml and povray. As Ethan points
out this will probably be very hard to maintain. The file=20
gnuplot-4.0.0/term/README defines quite clearly the way it shoud be
done. However in a povray or vrml terminal, this terminal standard
cannot be defined. I think it makes sens to separate 2D terminals (all
existing ones) and 3D terminals (vrml, povray, and hopefully more). The
core gnuplot core could be adapted to behave differently whether the
terminal is 2D or 3D (is is currently a completely 2D code) and the
actual translation of gnuplot internals in povray code could be made by
the terminal.

  Of course setting up the 3D code in gnuplot would require some work
from gnuplot devellopers, but I think it is worth the while. Especially
since the 2D code could be a projection of the 3D code. But I haven't
looked enough at gnuplots internal to know if this is possible.

  Thanks a lot for your and your student's work. I hope you will get
some help from people who know gnuplot's code better on this project. I
am willing to help (whenever I have time) with the terminal itself, but
I would rather not play with the core gnuplot function.

  Ga=EBl

PS :
  To answer ethan's suggestion about extending gnuplot's color
specifiaction to include alpha channel, yes, I think it would be great.