[Kstars-devel] OpenGL: the beginning

[Pablo de Vicente]

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El Domingo, 30 de Noviembre de 2003 21:36, Jason Harris escribió:
> Hello,
>
> > In my case './configure' did not complain that I did not have the
> > glutg3-dev package installed so when I typed 'make', it did not work. Now
> > I have installed glutg3-dev and it compiles fine.
>
> Yes, I didn't modify the configure script for this little test.
>
> > > Right now, it just displays the coordinate grid, and you can scroll
> > > with the arrow keys and zoom in/out with the +/- keys.  It seems really
> > > smooth on my system, but I have hardware acceleration, so I don't know
> > > how software openGL compares yet.
> >
> > My laptop does not have graphics hardware acceleration and it also works
> > smoothly here.
>
> Good to hear :)
>
> >  If the way we represent objects changes perhaps we should define at
> > least two more classes, a sort of 3dStaticPoint and 3dDynamicPoint. The
> > first one should represent a vector in cartesian and spherical
> > coordinates. The second one should inherit from the first one and should
> > have a constructor with 3dStaticPoint, t0, and v, where 3dStaticPoint is
> > the (x,y,z) position at time t0 and v is (vx,vy,vz) to allow for proper
> > motions. A position for time t would be obtained by doing:
> >  r' = r + v (t-t0)
> > SkyPoint should then inherit from 3dDynamicPoint. In this way the
> > transformation of coordinates from spherical to cartesian ones will be
> > very simple. We will also need some function to compute distances from
> > magnitudes, when parallax is not available. Are there objects without a
> > measurable parallax in the modified Hipparcos catalogs you made, Jason?.
> > And I have another question, does the Hipparcos catalog have Vlsr for
> > some sources?.
>
> One problem with this is that proper motions are defined on the surface of
> the celestial sphere; constant-velocity motions in RA and Dec will diverge
> from constant-velocity motions in X,Y,Z.  So I think we should still
> represent proper motions as delta-RA, Delta-Dec and then convert to X,Y,Z.
> Unless you are talking about actually placing the stars in a 3D volume,
> using their parallax distances.  I was thinking of still placing them on
> the celestial sphere.

 Yes, I was talking about placing the stars in a 3D volume, because then by 
moving the camera you can choose the origin of coordinates in the main 
KGLWidget. For example, you can choose to see the sky from somewhere in the 
Earth (classical view) or from 30 pc away from the Sun so that you can see 
the solar system and the stars, or you can move the camera 40 yr light away 
if you want to see the sky towards the Earth from a nearby star.

  If proper motions are given in delta-Ra and delta-Dec and we had Vlsr 
(radial velocity) we could get a complete 3D velocity.

regards

Pablo.
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