[Kstars-devel] Exporting to video

[Khudyakov Alexey]

Hi Yannis.

В сообщении от Вторник 02 февраля 2010 13:46:27 Yiannis Belias написал:
> Hi all,
>   Just FYI. Yesterday I made a video simulation[0] of the upcoming lunar
>  occultation of pleiades for my local astronomy club. So I used ktars and
>  I'd like to share a few things with you.
> 
Thank you for feedback. 

> 1. I used the script builder for start, but I found out I would have to use
>  a more "spiced up" shell script[attatched] for this job. (To tell the
>  truth, I was expecting something more javascript like...) 
>
I think you confim my suspicions about general uselessness of script builder. 
No ifs no loops no control structues at all. Pretty useless.

I'll write more in-depth e-mail on the subject later.

>  2. I had to use
>  for loops with explicit dates to increase the time interval. It would be
>  much better if I could just step forward for a specified time step.
>
Such function could be added.

> 3. I found out that when the kstars window was smaller than the capture
>  window, the output frames were blank[white] at that region. (Don't scratch
>  your heads - *netbook* :) )

>  4. The whole process of creating about 1000
>  frames is really slow.
>
Rendering is painfully slow. On my laptop it takes about a second to render 
screen with maximum stellar density. This should be improved but I don't know 
how.

>  5. I didn't find a way to display the time/date
>  info from within kstars, so I used the convert utility from imagemagick.
>
Yes there isn't function to do this.

> 6. The stars motion as you can see on the video is a bit "funky" :) I had
>  antialiasing switched off though.
> 
Without antialiasing stars positions are rounded to integer pixels. I think 
this could be fixed.

Curently stars are rendered using pixmaps. There are cached pixmap for stars 
of diferent size and color. It is possible to generate pixmaps for stars for 
each subpixel offset. This could be a speed advantage. I came up with such 
scheme to speed up drawing without sacrificing antialiasing.

There is a drawback. Cache grows up significantly. If images are generated for 
0.25 offset cache become 16x bigger. But this is not a big deal I presume.