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Problem with rendering patch object when FaceVertexAlphaData is given

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Sandor Toth
Sandor Toth on 19 Jan 2017
Answered: Sandor Toth on 19 Jan 2017
When I create a single patch object with different transparency and color per face, Matlab R2016b under OSX seems having a bug in rendering it. A simple example with two cubes gives the following plot, see Matlab code below.
The main problem with this image is, that the red cube should be in the front, and it is non-transparent (alpha=1), still I see the green cube behind. I tested the same code on R2015b and the rendering looks the same.
% vertices for a cube
Vcube = [0 0 0;1 0 0;1 1 0;0 1 0;0 0 1;1 0 1;1 1 1;0 1 1];
% faces for a cube
Fcube = [1:4;1 2 6 5;2 3 7 6;3 4 8 7;4 1 5 8;5:8];
% red color for the faces of the cube
Cred = repmat([1 0 0],[6 1]);
% green color for the faces of the second cube
Cgreen = repmat([0 1 0],[6 1]);
% non-transparent first cube (defined on all 6 faces)
A = ones(6,1);
% two cubes
V2 = [Vcube;bsxfun(@plus,Vcube,[2 2 -1])];
F2 = [Fcube;Fcube+8];
% color for the 2 cube
C2 = [Cred;Cgreen];
% different transparency for the two cubes, red one is non-transparent,
% green is semi transparent
A2 = [A;A/2];
clf
hPatch = patch('Vertices',V2,'Faces',F2,...
'FaceColor','flat','FaceVertexCData',C2,...
'FaceAlpha','flat','FaceVertexAlphaData',A2,...
'AlphaDataMapping','none');
axis off
axis equal
axis([-1 4 -1 4 -2 2])
view(3)
If this is a bug (I believe it is), is there any known workaround?
Thanks!

Accepted Answer

Sandor Toth
Sandor Toth on 19 Jan 2017
It seems a simple command fixed the problem:
opengl hardware
After running this command and replotting the figure, I get the following image:
Before the opengl was set to:
opengl hardwarebasic

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