[Kstars-devel] [patch] improve rendering time for stars by a factor of 20

[Jason Harris]

I'll probably add the patch soon.  I'm first trying to address a regression 
that James pointed out:

Now that we're using QPixmaps for the stars, we have the same "wobbling" 
problem we had in 3.5.  You can see this by dragging around the sky slowly 
and watching as the positions of the stars wobble slightly.  This actually 
still happens with the drawEllipse() code, but it's much less obvious.

The problem is not mitigated by activating antialiasing for slew-mode draws.  
I'm trying to find a way to force the pixmap to get resampled to the correct 
floating-point pixel coordinates, but doing so might take away (some of) the 
speed advantage we've found.  

Perhaps we can do something like store multiple versions of the pixmap cache, 
for stars centered on pixel edges vs. centered on pixel centers.

Maybe I should just commit what we have for now, and worry about the rest for 
4.1...

comments?

regards,
Jason


On Monday 24 December 2007 01:12:49 pm Akarsh Simha wrote:
> Hello
>
> > It works brilliantly here.  The patch looks pretty simple without
> > far reaching changes so I'm leaning towards including it in 4.0.
>
> Yes, it works here as well. It's much faster now, and I suppose it will
> be even better and seamless if we add the magnitude-limit at low zoom fix
> as well.
>
> I feel that important bugfixes like this should go into KDE 4.
>
> Regards
> Akarsh.