quiver arrows always appear below semitransparent layer

I am attempting to plot quiver arrows on top of a semitransparent pcolor layer. However, the arrows only appear below the semitransparent layer. It does not seem to depend on the order in which I plot the layers, and uistack has no effect. How can I get the arrows to appear on top?

figure('renderer','opengl')
imagesc(A); hold on
colormap(gray(256))
freezeColors; 

% Overlay semitransparent ice speed:
h = pcolor(x,y,speed)
colormap(jet)
shading interp
set(h,'facealpha',.4)

% overlay velocity vectors: 
hq = quiver(x,y,vx,vy,'k');

[Joseph Cheng]

odd i can't seem to recreate your results. i created this to test it out.

figure('renderer','opengl')
base = imread('circuit.tif');
imagesc(base);hold on
colormap(gray(256))
freezeColors;
trans = peaks;
trans = imresize(trans,size(base)/2);
trans = pcolor(20*trans);
colormap(jet)
shading interp, set(trans,'faceAlpha',.4);

[x,y] = meshgrid(1:5:272,1:5:280);
u = cos(x).*y;
v = sin(x).*y;
quiver(x,y(end:-1:1,:),u,v,'k')

does it still happen?

[Chad Greene]

Still happens. I have R2012b on a Mac OSX 10.8.5.

[Joseph Cheng]

odd... still can't reproduce it and i jumped all way back to 2011a. I am using windows so maybe that's it? The only thing i can think next is changing the children order as changing the renderer to either zbuffer wouldn't let you have transparency?

 get(gca,'Children') and set(gca,'Children',%reordered%)

[Chad Greene]

Strange. Reordering children doesn't work either. Perhaps it's a Mac/OpenGL issue, and indeed, I need OpenGL for the transparency. Thanks for trying, Joseph.

Answer 1

[Sean de Wolski]

Probably an OpenGL issue but one thing you can do is use quiver3 with z set to some positive amount greater than the max of surface. Set v component to zero as well.

[Chad Greene]

Good thinking, Sean. This workaround is not perfect, but it definitely gets the job done.

That's set the w component that needs to be set to zero.

In Joseph's example, his quiver line can be replaced with

quiver3(x,y(end:-1:1,:),ones(size(x)),u,v,zeros(size(x)),'k')