How to change from Unity 2D to 3D?

Question

I have been trying to run MyUnity, and it's been working fine until today, when it comes up with the message:

So, apparently I am running Unity-2D. So I did a little command-line search withecho $DESKTOP_SESSION and sure enough, it spat out simply "ubuntu-2d".

I have been using Ubuntu Tweak and perhaps I did something stupid in there, but I don't think it even had a feature like that. I've also noticed the clear differences in Ubuntu 2D to Ubuntu 3D, as well.

I have 12.04 Ubuntu. So is it possible for me to "revert" back to Ubuntu/Unity 3D?

Edit: My graphic card is a 2GB dedicated AMD Radeon HD 7750, which I've come to think needs to be upgraded 12.6 version. I'll try this and let you know the of the outcome, thanks so much for helping.

Result: after successfully updating the graphics card, I now can run 3D. Thanks so much to all of you and I'm sorry for such an unusual question!

Solution

I suggest you to have a look at the 2 answers of that question
You will learn out to configure the file /etc/lightdm/lightdm.conf

Comments

[Admin]

do you have autologin enabled? If yes, logout and login to the unity 3d session by clicking small ubuntu logo in the login field and selecting 'Ubuntu' session

[Admin]

Unity3d is usually the default option, and 2d is only selected unless if the hardware has problems with the 3d version. What graphics card is there?

[Admin]

Thanks so much for your answer, I've come to think I need to update my graphics card - which I will now mention in the question description - before I can run Unity, which seems a little odd, considering I got this computer last week!

[Admin]

If I unterstood correctly, you've updated your graphics driver (Catalyst/fglrx) to the latest version (you haven't replaced your old graphic card with a new one you bought), so the problem was caused by the driver not supporting 3D on your hardware.

[Admin]

Yes, the fglrx. And yes, it was. So I suppose the name of the card is completely irrelevant to the driver name? Gosh, sorry I'm a noob hahaha

[Admin]

The name of the card leads you to the engineering name (which is "Southern Islands" for the HD 7750). Cards with the same engineering name are very similiar, while cards with a similiar marketing name can be totally different on the technical level. Knowing the engineering name, you can look up on x.org/wiki/RadeonFeature which features the free driver supports on your chipset. For Southern Islands, all the 3D features are set to "TODO", so you are forced to use the prorietary driver for 3D support.