Since ATI or nVidia graphic driver is not included on the default Elementary OS Luna installation, we need to manually install the driver and activate the 3D features in ATI or nVidia graphic card. Without this restricted driver, we still can use Elementary OS Luna on a laptop or PC but there is no 3D or 2D supports. So, for better user experiences in graphic imaging and processing, I suggest you to enable this 3D feature on your graphic card.
This tutorial is going to show you how to enable the 3D graphic proprietary driver on Elementary OS.
First, go to System Settings.
Next, click Additional Drivers
On the Additional Drivers window, you will see list of available drivers you can use. Select one of them and press Activate. Elementary OS Luna will download and activate the driver. A reboot may required to enable this new driver.