BTW - the MBA is not the best platform for rendering. You really should get a higher performance machine for that - probably a quad-core MBP if you need a portable. Get one with an SSD in it (or put one in yourself)
Have to agree with technOlady, if you will be rendering 3D on a very stressing manner, you need more juice on your computer and a better thermal system to deal with the power dissipation.
However, all depends on what kind of 3D rendering you will be doing, for example, the reason I got my MBA is because I saw everybody at my college using it for 3D modeling; I study engineering and we use SolidWorks for our 3D models. A very heavy application. I have not tried it yet myself, but they are pretty comfortable with it, no lag, heat is palpable and obviously, as any graphics intensive application, you must use the power adapter.
I just observed you also said "gaming".. this is a completely different 3D rendering since it loads as iterations per second, get a 15in rMBP, you will get a gaming graphics card, the power, and a better thermal system.
If you do gaming on a MBA, it will get the job done and won't fry nor shut down, but it will put a lot of thermal stress on the components and will decrease the life of each component. Fans will kick at their max and you might be quite uncomfortable feeling so much heat on your hands as you play the game using the keyboard, some people don't mind this.
3D rendering (gaming) will always require better specs than 3D modeling.
Hope this help you out!
(For all the trolls out there, please make sure you google up 3D modeling vs. 3D rendering before posting something).