Originally Posted by sperron
has no real down side
You have to understand the nature of game engines, v-sync, varying framerates and the consequences of not maintaining a rock-solid framerate when using interlaced methods of rendering.
Yes, there is a very real downside and it is what seperates the application of gaming and linear video.
Linear video (broadcast/tape etc) can use field rendering (two different fields) simply because it can maintain a solid framerate. Game engines however are a completely different bag.
Inorder for a 60 frames per second game to render at 1080i with field rendering (each field is independant time stamp relative to the game engine), the game engine must maintain that 60fps without faultering. The result of a frame drop would cause serious anomilies to be visible on screen as the incoming frame would not match the outgoing one and you'd essentially have a garbled screen as the two mismatched fields interwove.
To avoid this, the framerate is locked to 30fps and the engine renders each field from the same singular game frame. This insures that any drop in the framerate is percieved as nothing more than a slight pause as the dropped frame/s are skipped and a totally new frame (made up of two identical fields) are then presented.
Now the above is not always true of every 60fps game, if the framerate can remain an unshakeable 60frames per second, then field rendering would be perfectly acceptible (and demonstable), but you won't find any retail 360 game which are able to do 60fps without dropping frames at some point. Perhaps some Arcade titles are out there that are more than capable of maintaining 60 solid, but even if they could, its not clear if the hardware is smart enough to be told to spit it out when 1080i is the selected resolution.
The 360 isn't so much 'throwing out half the frames' as you put it, the fact is that once you select 1080i as your output resolution, you are instructing the game's engine to only render at 30fps. The framerate's fate is determined as soon as you select 1080i in the display settings menu.
But please, disprove the above. These are the AV Science forums after all and I've given a list of everything needed inorder to blow my arguments out of the water with cold hard visual evidence of field rendering if it does infact exist.