Question

Ok, so the patch function lets us draw multiple polygons with e.g.

patch(X,Y,'r')

where X and Y are m-by-n matrices. This draws n polygons with m vertices.

But what if I want each of those n polygons to have a unique alpha transparency value?

patch(X,Y,'r', ??? SOME CODE TO USE A VECTOR OF ALPHA VALUES ???)

The documentation is confusing me to death. I can’t use a for loop, since I need to draw many patch objects very quickly. Could somebody kindly provide a code example? Thanks everyone.

Answer 1

Looks like the FaceVertexAlphaData property is the key: Here is some sample code:

X = [...
    1  2  3 ; ...
    4  5  6 ; ...
    7  8  9 ; ...
    10 11 12];
Y = [...
    2  5  8; ...
    3  6  9; ...
    1  4  7; ...
    -1 3  6];
h = patch( X, Y, 'r');
set(h,'FaceAlpha','flat','FaceVertexAlphaData',[.2; .4; .8])

docsearch patch properties for more information.