Re: [Flightgear-devel] Making of: jitter.png (Unix)

[Roy Vegard Ovesen]

On Saturday 19 August 2006 09:44, Melchior FRANZ wrote:
> * Roy Vegard Ovesen -- Saturday 19 August 2006 09:36:
> > I've also used kst to plot properties in real-time. I used Flightgear's
> > own logging.
>
> How are you doing it? Via FIFO or by writing to a file and letting kst
> read from it?

I use FlightGear's logging system to log to a csv file, and let kst read that 
file. Kst updates as the file grows. The csv file has headings at the top and 
the first column is the time in seconds since start of fg.

I use the "Data Wizard" in kts to open the csv file. Kts recognises the column 
names and it automatically creates a culumn called INDEX. The INDEX column is 
probably supposed to be used for the horizontal x-axis, but since we already 
have a timestamp comlumn it's better to use that one for the x-axis.

It makes sense to check the "Read to end" checkmark in the select data screen 
of the wizard. After I'm done configuring kst and setting up all the plots 
that I need I save the kst plot file. The next time I start fg with logging I 
open that plot file in kst and it will of course read the data that fg is 
putting into the log file. I don't have to go through the wizard and the 
configuration of the plot layot every time.

> The most obvious way -- directly piping -- didn't work for 
> me, as kst gives up if there are no data within a few seconds. And fgfs
> takes a while to spit out anything. I "complained" to the kst mailing list
> and don't know yet what they think. But the FIFO isn't that bad for now.

I haven't tried the FIFO method, but the log file method works grat for me. 
Another advantage is that the data is stored in the log file. Not knowing 
everything about FIFOs I'm guessing that the data is only "stored" in kst 
with this method.


-- 
Roy Vegard Ovesen

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