Re: Do we really need to replace gnuplot?

[Alexander Barth]

On 10/15/07, Shai Ayal <address@hidden> wrote:

On 10/15/07, John W. Eaton <address@hidden> wrote:
> On 15-Oct-2007, Shai Ayal wrote:
>
> | But are you willing to sacrifce offscreen rendering for them?
>
> Precisely what do you mean by offscreen rendering?

I mean the ability to produce a plot in a file (e.g ps or png) w/o the
need for opening a window or indeed using any graphical capabilities
in the computer. gnuplot does this easily, However OpenGL is meant for
screen rendering, so even if you wish to produce a png file, you must
first render the scene to the screen and then convert it to a png
file.

There might be a solution for this using OpenGL pbuffers. I'm looking into it ..

Shai

You can do off-screen rendering in opengl with GLX Pixmap and OS Mesa.
For GLX Pixmap you need a connection to a X server but no window is displayed. This is not necessary for OS Mesa. A nice overview can be found here:

http://www.mesa3d.org/brianp/sig97/offscrn.htm

Also, toolkits such as GTK (gtkglext) provide a higher level interface for off-screen pixmaps.
http://gtkglext.sourceforge.net/reference/gtkglext/gtkglext-gdkglpixmap.html

The advantage of using a toolkit for off-screen rendering is that your code is probably more portable.


Alex