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Thread: Multiple Real-Time Curves Not Overlapping Properly

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    Default Multiple Real-Time Curves Not Overlapping Properly

    Hello,

    I am trying to add two real-time plot curves to one plot object. The curves are created from captured voltages and are similar to oscilloscope curves. I need to show both curves on top of each other for reference. What is happening is each curve is only being displayed in half the width as each curve seems to be overwriting the other curve with a black rectangle, making half of it disappear during replots.

    Here is an image:

    overlapping_curves.jpg


    Is there a way, with QWT, to draw two curves on top of each other without half of the curve disappearing?

    Thanks,

    -brian

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    Default Re: Multiple Real-Time Curves Not Overlapping Properly

    Quote Originally Posted by brianbat View Post
    What is happening is each curve is only being displayed in half the width as each curve seems to be overwriting the other curve with a black rectangle, making half of it disappear during replots
    No this is not happening - nobody fills rectangles when drawing a curve. It looks more like that the bounding x interval of the curves is different: check your samples.

    Uwe

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    Default Re: Multiple Real-Time Curves Not Overlapping Properly

    As the curves are being displayed I can see the full curves being displayed with half of it is flashing on and off. Like I said when I display each curve separately I see the curve fill the entire view space so the bounding X interval is fine.

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    Default Re: Multiple Real-Time Curves Not Overlapping Properly

    No you don't see anything as the x axis is disabled.

    I would guess, that you have autoscaling enabled and the x-axis changes, when you enable/disable a curve: try your application with having the x axes visible.

    Uwe

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    Default Re: Multiple Real-Time Curves Not Overlapping Properly

    Quote Originally Posted by Uwe View Post
    No this is not happening - nobody fills rectangles when drawing a curve. It looks more like that the bounding x interval of the curves is different: check your samples.

    Uwe
    I captured three videos showing what is happening. The first two videos show the separate single plotted curves. The third video shows the two curves together in QWT and demonstrates the issue I am having.






    Added after 9 minutes:


    Quote Originally Posted by Uwe View Post
    No you don't see anything as the x axis is disabled.

    I would guess, that you have autoscaling enabled and the x-axis changes, when you enable/disable a curve: try your application with having the x axes visible.

    Uwe
    Hello, yes autoscaling is on and the x-axis was disabled. I tried enabling the x-axis and the plotted curves are still alternating on one half of the plot.
    Last edited by brianbat; 9th May 2013 at 18:59.

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    Default Re: Multiple Real-Time Curves Not Overlapping Properly

    Quote Originally Posted by brianbat View Post
    Hello, yes autoscaling is on and the x-axis was disabled. I tried enabling the x-axis and the plotted curves are still alternating on one half of the plot.
    Of course they do, but is the axis range changing, when you enable/disable curves ?

    More interesting than your videos are the bounding rectangles of your curves: I'm pretty sure the x interval is different: the x coordinates of the second curve are above the first.

    Uwe

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    Default Re: Multiple Real-Time Curves Not Overlapping Properly

    Sorry Uwe, I just understood what you meant. I set the same x values for both curves and everything is fine.

    Thanks for your help and patience.

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