The 64 Cube Ending is the last ending in the game. In order to get it, you need all 32 normal cubes and all 32 anti-cubes. Whether or not you got any heart cubes or artifacts does not affect whether or not you get this ending.
The ending starts with Gomez exploring the starting area with the camera zooming out. The camera zooms out incredibly far and it suddenly seems that all the areas of the game are hexagons suspended in time and space. The camera keeps zooming out until everything merges together and the whole screen is full of static. Then the credits roll. Afterwards, you can get the 3D Glasses.
After this ending, there is nothing more you can do in this game, unless you didn't get all the heart cubes and collectables. Also, not a lot of known players have gotten this ending, so if you got it, you have some bragging rights (especially if you got everything the game has to offer).