slow graph when zooming in on x-axis

[pete]

In LabVIEW 6.1 on a Windows 2000 platform, I am using an XYgraph that displays anything between 10 and 80 curves simultaneously. Each curve has 2001 points. Even if I have only 10 curves, when I zoom in on the x-axis LabVIEW sometimes slows down terribly. Even moving the cursor takes minutes. After autoscaling the x-axis everything is back to normal, sometimes the application speeds up by itself again. What can I do about it?

[Mads]

How do you zoom, are you using the zoom tool of the graph, or is it a zoom functionality you have coded yourself?

Do you update the graph values during the zoom operation?

Have you verified that there is nothing in the rest of the application (or other apps running on the computer) that requires a lot of processing just when you are having problems zooming? If you e.g. put the 10 curves on a graph, make it the default values of the graph and copy it to another VI and then zoom (not running any code), how is the performance?

If the plots are set to be antialiased, try disabling that...Antialiasing can give a significant performance penalty in some cases...

[pete]

Thanks Mads,

Got the solution, your remark about the anti-aliasing was just the trigger.

I zoom in using the zoom tool of the graph, I don't update the data. No anti-aliasing is enabled. On a copied version as you suggested the process is still slow. On a dummy version of the vi, I switched some curves on and off, and found that it all works fine untill I have 2 ore more DASHED lines. 80 solid lines is no problem.

So it appears that zooming in on dashed lines can give some speed problems in XY graphs, using solid lines is fast.

Thanks,

Pete

[Greg_McKaskle2]

> So it appears that zooming in on dashed lines can give some speed
> problems in XY graphs, using solid lines is fast.
>

Interesting. I almost chimed in asking about dashed lines, but decided
not to since that problem had been worked around, or at least I thought
it was.

The core issue is that Microsoft video takes forever to draw dashed wide
lines that are clipped. We were seeing a ten second redraw of a pretty
simple curve. Microsoft admits the problem and says they have no plans
to change it.

Our workaround was to draw wide dashed lines one segement at a time, as
the slow part seemed to only be the polyline portion.

Please submit your VI, or just a panel with your graph copied onto it
and the value made default and file it as a bug.
We will see if we
can't find more workarounds for Microsofts wonderful graphics.

Greg McKaskle

[pete]

Hello Greg,

Sorry for my late answer, we had a national celebration day here in the Netherlands for the honour of the queen.

Anyway, I tried to remove all the unnecessary stuff from the graph vi, and implement some artificial data. However, now the problem does not occur anymore! It's still quite slow, but not as bad as before. I attach the vi anyway. It generates 80 plots of a sine wave, all having a small phase difference. You can add some 'noise', I thought that could slow the plot down but that's not the case. By clicking the control that is an array of booleans you can selecte which plot appears in the graph. By default, the first 40 are plotted and the next 40 are not. See what you can do with it.

regards,

Pete