Problems set transparency not supported with software OpenGL histogram2

When I try to modify the transparecy of a histogram2 using FaceAlpha, Matlab (2017a accademic licence) return the warning:

Warning: Transparency is not supported with software OpenGL renderer.
Consider setting figure renderer to 'painters'.

I do not understand the warning. How do I set properly the transparency?

Answer 1

[Walter Roberson]

set(gcf, 'Renderer', 'painters')