RE: [Visualpython-users] Snapshots/Raytracing: Ari out of control :)

[David S. <dsc...@cm...>]

> I figured I better clear this up before it gets any more absurd.

I figured I better clear this up before it gets any more absurd :)

> 1) Raytracing. If the only reason you want to raytrace is to have
> a picture
> of what's on the screen, for goodness sake *TAKE A SCREENSHOT*.
> Ctrl-Alt-whatever in windows, use the xwd(1x) utility in Unix[1].
> I *still*
> haven't heard why anyone wants to make raytracings in the first
> place -- it
> seems like a lot of work if all you want is textures. And without
> textures,
> it's not going to look any different than the GL renderings.

Wrong.  Raytracers use analytic curved surfaces, so they will render much
better spheres, etc.  They can do specular highlights, reflection,
refraction, and all manner of other neat stuff with materials.  As I noted
in another e-mail, there's no reason that some extra attributes can't be
tacked on to Visual objects to control these features.

I think it's an excellent idea.  I just don't have time to do it myself.

> 2) Non-interactive mode (i.e. what you'd use to make VPython a
> cgi script).
> This presents a real problem. Typically a cgi script is run as
> user nobody.
> VPython wouldn't be happy under those circumstances -- it needs control of
> the console and X running -- in short, it needs the DISPLAY environment
> variable validly set.

Every GL implementation I've seen (I confess to not knowing anything about
Mesa) can create a GL context pointing at an offscreen surface and software
render to it.  I would be very surprised to learn that no one has ever
implemented a CGI script that way.

> The Visual library was *not* designed to be run in any
> non-interactive mode.

Since I designed it, I think I can confidently say that it *was* designed
with similar things in mind.  They just haven't been implemented.  If
someone is willing and competent to write some C++ code to do this, I will
be happy to explain exactly how it can be done.

> If you were willing to forgo any pretense of security (read: Ari
> says this is a *bad* idea)

Yes, this is a bad idea.  However, the existence of a bad solution doesn't
prove the nonexistence of a good solution.

Dave