How to achieve Graph background effect

[AndrewMadry]

I came across this post: 

https://forums.ni.com/t5/LabVIEW/Waterfall-display/td-p/2754750?profile.language=en

when looking for ways to do waterfall plots:

Does anyone know how to do the effect on the top graph, showing a spectrum, where the area below the plot is shaded?
Setting the background plot image property could make a vertically shaded background pattern matching the Y axis.
But this wouldn't work to make the area above the plot line transparent. I can see that it would be possible by updating the background image, to match the plot, each iteration of writing to the graph, but that seems like a lot of overhead.
Any suggestions for how this effect might be achieved?

[GerdW]

Hi Andrew,

several options:

• use the background image property of a graph and draw that image as needed
• use a 2DPictureIndicator to draw the complete graph display on your own
• use the IntensityGraph as suggested in your linked thread…
• use one of the packages at VIPM, which offer advanced graph capabilities

[wiebe@CARYA]

Another option is to make multiple plots, and set the fill options of the plots.

So you'd have your data, and then a plot with either data - x or data/n. This plot will be below the data. Set the fill options to fill from data to the plot. Repeat for each color in the gradient.

I'd probably use the picture control, because I'm familiar with it. But this trick will be a lot simpler if you can get away with it. 

[wiebe@CARYA]

This effect is more like your posted image:

The transparency is going to be difficult with this technique.

With the picture control background, coordinate conversion will be the difficult part..

[MIG · Accepted solution]

Just for fun, here is my attempt at doing it with a background picture.

[AndrewMadry]

Thankyou for great suggestions. MIGs example achieves the exact effect!

But it seems it would be a bit of overhead particularly if the graph takes up a large number of pixels on the screen. But for small graph it should be fine. Wiebe's suggestion is a clever compromise.

I also tried an effect where a single background image is written, then an extra plot is added with fill to +Inf in black. This covers up the grid lines though, so it doesn't look as nice.

I added it to MIG's example - see attached.