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Intensity Graph Z Autoscale bug? [8.5.1]

Hi I am lately having hard times with intensity indicators. They seem to be quite buggy. My new discovery is strange working Z autoscale. My understanding of Z axis autoscaling is that it finds maximal and minimal magnitude in data - the minimum is assigned to the lowest element in ZScaleMarker.Values[] and maximum to the highest one. What is in between is recomputed with uniform step (I mean if there are more ZScaleMarker.Value[] elements). That's the way how intensity chart works.

But if I turn on autoscale and feed the graph it updates the ramp ticks BUT it doesn't update the ZScaleMarker.Values[] - is that expected behavior? In addition if I move the VI behind the screen border the ramp changes the color to white - I believe it is because it starts to respect the values in ZScaleMarker.Values[] (they are still 1-white, 0-black because they aren't refreshed) and thus the actual real values are out of range.

Nevertheless in all cases the data are depicted correctly only the ramp behaves weird.

 

Could somebody explain this to me?

Message Edited by ceties on 08-29-2008 08:33 AM
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I just realized that you even don't have to do the 'hide trick' - it's enough if you just stop the VI it results into white ramp as well
Message Edited by ceties on 08-29-2008 08:36 AM
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Hi ceties,

 

Just a quick note that may explain what is going on here.  Markers actually behave as if they are absolute if you use AutoScale Z.    The symptoms of this are what you seem to be describing.  I think this may be expected behavoir, but it certainly isn't intuitive.  I will take a look to see if R&D has looked at this.

 

In any case, we should be able to write to the ZScaleMarker.Values[] property to set it appropriately for our data, just as you have initialized it in your VI.

Brian A.
National Instruments
Applications Engineer
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Yep. To create own autoscale is a solution. But if that is an expected behaviour I don't understand why Intensity Chart behaves different and also why the ramp colours (not markers) doesn't update untill I 'hide it' or stop the vi...Anyway thanks for taking care of it!
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Good point.  I did find reference to Markers being absolute dismissed as expected behavior (for some reason..).  Seems like something that would be good to file as a product suggestion.  However, your point about the color not updating until the VI finishes execution needs to be addressed.  Toward that end, this was reported to R&D (# 124959) for further investigation.  

 

Cheers, 

Brian A.
National Instruments
Applications Engineer
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