I was talking to Bruce Dawson, one of our senior software design engineers here, about some questions I had around 1080i and 1080p. Frankly, I was particularly curious about why Sony has continued harping on 1080p as being "TrueHD", especially since the 360 has enabled 1080p output as well (coming soon to homes near you!) I was trying to figure out if I was just missing something, and his emailed answer was particularly clear and helpful to me, and since there's nothing confidential here I thought I'd share it with you.
The really interesting statistic that popped for me is how much less time a game console has to render a 1920x1080 scene versus a 1280x720 scene. (Remember this is on the same console, whichever one you like. This is not a comparison of different console's rendering capabilities to each other.) Simply put, for a 1080i/p game the console has 55% less time per pixel to render any special effects, anti-aliasing, illumination, etc. than for a 720p game. Yes, even Resistance has fallen off the bandwagon and admitted they can't hit 1080i/p as previously claimed. (It also helps explain why Gran Turismo HD is so underwhelming.)
* 2.25x: that’s how many more pixels there are in 1920x1080 compared to 1280x720
* 55.5%: that’s how much less time you have to spend on each pixel when rendering 1920x1080 compared to 1280x720—the point being that at higher resolutions you have more pixels, but they necessarily can’t look as good
* 1.0x: that’s how much harder it is for a game engine to render a game in 1080p as compared to 1080i—the number of pixels is identical so the cost is identical
There is no such thing as a 1080p frame buffer. The frame buffer is 1080 pixels tall (and presumably 1920 wide) regardless of whether it is ultimately sent to the TV as an interlaced or as a progressive signal.
* 1280x720 with 4x AA will generally look better than 1920x1080 with no anti-aliasing (there are more total samples).
