fill plot and transparency < 1 removes lines of x-axis and y-axis. Why?

The following code works nicely if transparency is 1. If transparency < 1 the lines of the x and y-axis disappear. Why is that?

clear all; close all;

color = 'r';
alpha = .3;

x = linspace(0,1,10)';
y1= x.^2;
y2= 2.*x.^2;

figure;
hold on;
plot(x,0.5.*(y1+y2),'b','Linewidth',2.);
h = fill([x; flipud(x)],[y1; flipud(y2)],color);
set(h,'FaceColor',color,'EdgeColor',color,'FaceAlpha',alpha,'EdgeAlpha',alpha);
box 'on';

[GunnarG]

For the case, other people are searching for a solution:

This link shows a simple solution: just put the axes on top at the end:

set(gca, 'Layer', 'top');

Answer 1

[Walter Roberson]

I think this might be the same thing Jan described at http://www.mathworks.com/matlabcentral/answers/25028-bug-in-pcolor

OpenGL is the only renderer that supports transparency, so possibly your figure is being rendered by painters or zbuffer until you add transparency after which it hits the OpenGL-specific bug.

Answer 2

[Sean de Wolski]

http://www.mathworks.com/support/solutions/en/data/1-5X41G7/index.html