Surf plot mesh looks jagged when I set FaceAlpha

Below is the example given in the "surf" documentation. The mesh looks smooth when `FaceAlpha` is not included but it looks jagged when it's transparent. Is this a graphics card issue or can it somehow be fixed?

 [X,Y] = meshgrid(-5:.5:5);
 Z = Y.*sin(X) - X.*cos(Y);
 s = surf(X,Y,Z,'FaceAlpha',0.5)

[Walter Roberson]

Let me think... You are using r2013b or r2014a or so? If so then there was bug having to do with opengl use, which gets enabled automatically when alpha is used.

[Hongbo Zhao]

I'm actually running it on R2018a. In fact when I try the example in the browser it also looks jagged https://www.mathworks.com/help/matlab/ref/surf.html?s_tid=doc_ta

Answer 1

[Leone Campos]

Based on Jan's answer I was able to solve the problem on my PC (Windows 10) using

opengl hardwarebasic

Code

from https://www.mathworks.com/help/matlab/ref/mesh.html

opengl hardwarebasic
% opengl hardware
% opengl software

[X,Y] = meshgrid(-5:.5:5);
Z = Y.*sin(X) - X.*cos(Y);
s = surf(X,Y,Z,'FaceAlpha','0.5')

With software

With hardware

With hardwarebasic

[Hongbo Zhao]

Thank you @Leone Campos This works perfectly for me (windows 10 + R2021a)! We finally have a solution after 3 years. This is in fact very important since you will often want to show the entire surface with the lines still looking good.

Answer 2

[Jan]

It looks nice in my Matlab 2016b/Win10. Setting the Alpha blending enables the OpenGL renderer. If this causes troubles, try:

opengl software

Does this help? Do you have the current versions of the drivers installed? Which OS are you using? Can you post a screenshot such that "looks jagged" gets more clear?

[Hongbo Zhao]

opengl software doesn't help. But when I type opengl info it does show the driver. See the mesh below not setting alpha looks much smoother than when alpha=0.5. In fact, even when I set alpha=1, the mesh still looks pixelated.

[Walter Roberson]

Setting Alpha at all forces OpenGL to be used.

[Jan]

@Hongbo Zhao: Thanks for posting the screen shot. This clarifies immediately that this is the expected behavior. Alpha blending works in the OpenGL renderer only, but then the line smoothing is not enabled (for reasons unknown to me).