variable transparency in surface plot

I'm trying to represent as a colored planar surface in 3d and would like to use variable transparency across the entries using the surface command. If 'CData' is an array of size m x n x 3, does 'AlphaData' have to be three-dimensional as 'CData' or of size m x n?

The following code does not produce the intended result for 2-dimensional 'AlphaData' and makes matlab crash after executing the program if I use a 3d array for 'AlphaData':

CData = rand(4,4,3); % random color data

[X,Y] = meshgrid(0:0.25:1,0:0.25:1);
Z = zeros(size(X));

figure(1)
clf
h0 = surface(X,Y,Z,'CData',CData,'FaceColor','texturemap')
h1 = surface(X,Y,Z+1,'CData',CData,'FaceColor','texturemap')
view(10,60)

AlphaData = ones(4);
AlphaData(2:3,2:3)=.5;
set(h0,'Alphadata',AlphaData,'FaceAlpha','texturemap')
set(h1,'Alphadata',AlphaData,'FaceAlpha','texturemap')

Any helpful hints as to what goes wrong would be very much appreciated.

[Jan]

What does "Matlab crash" exactly mean?

[felix]

"Crashes" means that Matlab produces a figure but after any further action from my side (moving the mouse), a window opens stating that "Matlab has encountered an internal problem and needs to close" because of a segmentation violation.

Answer 1

[Walter Roberson]

AlphaData must be two dimensional.

For FaceColor of 'texturemap', CData does not need to be the same size as the ZData: it will be "stretched" to fit the ZData.

For FaceAlpha of 'texturemap', AlphaData does not need to be the same sze as the ZData or the CData: it will be "stretched" to fit the ZData.

[felix]

My statement of the problem was probably a bit too brief:

1. When running the code with two-dimensional AlphaData, matlab produces surfaces where the inner part (AlphaData(2:3,2:3)=0.5) is completely transparent instead of half-transparent. The same happens if I replace 0.5 by 0.99.

2. For AlphaData(2:3,2:3)=1 on the other hand, the change of transparency by the set commands should have no effects. In this case however, all surfaces become nearly transparent!