How to test 3d acceleration?

The command below could provide at least a partial answer to your question.

/usr/lib/nux/unity_support_test -p

The command tests whether your video adapter will support Unity 3D. While it does not test 3D acceleration per se, it will at least test for the 3D features which Unity 3D requires.

And, what the heck, it comes with Ubuntu so all you have to do is open a terminal window and run it. ;-)

Here is an example of the output.

irrational@VBx64:~$ /usr/lib/nux/unity_support_test -p
OpenGL vendor string:   Humper
OpenGL renderer string: Chromium
OpenGL version string:  2.1 Chromium 1.9

Not software rendered:    yes
Not blacklisted:          yes
GLX fbconfig:             yes
GLX texture from pixmap:  yes
GL npot or rect textures: yes
GL vertex program:        yes
GL fragment program:      yes
GL vertex buffer object:  yes
GL framebuffer object:    yes
GL version is 1.4+:       yes

Unity 3D supported:       yes

An easy way to test it (not a benchmark test though) is using glxgears.

sudo apt-get install mesa-utils

then in a terminal type: glxgears

It will display your frames per second (fps).

More info here.