Why does the "alpha" function make the left and bottom borders of my figure disappear in MATLAB?

The left and bottom borders of the axes disappear (although the ticks are displayed as expected - with 'box on') when I change the transparency of the plot.

Here is my code:

       figure
       area(1:10,1:10)
       box on
       alpha(0.2)

Why does that happen?

Answer 1

[MathWorks Support Team]

This is due to a bug when using transparency in MATLAB. OpenGL does not render the borders correctly.

This issue occurs when a plot with some transparency has its edges overlapping with the edge of the figure.

Possible Workaround on Mac:

Increase the axes offset by a small value depending on the scale of your figure. For example:

       figure
       area(0:10,0:10)
       box on
       alpha(0.2)
       set(gca,'xlim',[0 10.001])
       set(gca,'ylim',[-0.001 10])

Possible workaround on Windows and Linux:

1. OpenGL is the renderer that MATLAB uses to handle transparency. By default, OpenGL runs in hardware acceleration mode to increase performance. Use OpenGL in software mode instead:

       >> opengl software

Make sure to run this command before opening a new figure.

2. Once OpenGL is set to run in software mode, slightly increase the x-axis limit to make the right border reappear:

       figure
       area(1:10,1:10)
       box on
       alpha(0.2)
       xlim([1 10.001])

This should also fix issues with the borders of the legend box.

[Adam Danz]

I've been dealing with this bug on matlab vs 2014a for a few days and wanted to share my solution.

Slightly increasing the xlim/ylim partially solved this issue for me on some occasions but unfortunately each subplot needed different tiny offset values for the axes to fully appear.

My code was setting transparency (alpha) of objects in a plot and then setting axis limits. The axes disappeared after setting the axis limits. I changed the order of these commands so that axis limits were set before setting transparency. This fixed the problem for all of my subplots that were affected by this bug. Hope that helps.

Adam Danz