Recently on Bungie.net int he Bungie Weekly Update, they confirmed that Halo: Reach is indeed using a brand new engine. With that also came some information that the trailer we all saw was really not running real-time technically speaking,
The Halo: Reach trailer was produced directly in our new game engine using real game assets. Because the game is still in the midst of development, which means things like framerate are still in flux, we do something called a “frame dump” that lets us spit out the content, frame by frame, and then compile it back as the video you all saw on Saturday. We can actually run this same cinematic right now, within the latest game build, but it’s not always at the consistent smooth framerate of the final game (yet)
Well, that’s as close to real time as you can get. I’m sure the actual product will look and run no different. Bungie then went on to say that trailer represents the “visual bar” for the final game and that the trailer and actual game should be “near identical” next fall.
This trailer absolutely represents our visual bar for the final game and is near identical to what you’ll see next Fall. The single biggest difference between this trailer and the final game will be the extra generous amount of anti-aliasing (the smoothing of “jaggies” or edges of pixels) present in what you’re watching right now but rest assured that Reach will be significantly improved in this department compared to Halo 3. (The extreme “AA” in the trailer was due to the “frame dump” mentioned above.)
So they gave it a little more “AA”(anti-aliasing). This isn’t something that is going to effect the visuals of that game that badly. You will probably notice a few more jaggies here and there, something that sometimes can’t be helped. Large amounts of “AA” are hard to pull off in real time. Especially on consoles.
It seems like after what they did with Halo 2 and Halo 3, they aren’t showing off anything not in the game or that will be dulled down. We all remember the epic Halo 2 level from E3 that never made the game, and the Halo 3 reveal trailer that looked 10x better than the actual game. It looks like they aren’t doing anything of that sort this time around. That’s good to know.
Bungie Weekly Update [Bungie]

To me it sounds like there combining 3 Halo games into one. Maybe it’ll work out.
Oh here we go… -_____-
what i have come to notice is that in a fast paced game AA doesn’t play that big of a part. If you compare 2 stills then you will see a very large difference, but if your constantly moving, you will not notice it.
this worries me a bit, because this is EXACTLY what they said about halo 3 after that first trailer, first they said that it was in game and that was what it would look like, then they said that the trailer was what the game was going to look like (or atleast pretty close to that) when the game released, obviously they missed the mark, and now with halo reach, “the trailer which is going to be revealed at the vga’s is all in game” technically yes it was, but at the same time it was sort of an aim trailer, thats what they want the game to look like and run at when the game releases, im taking this with a very large grain of salt, if they can pull it off awesome, i do not want a halo 3 with better graphics, i want an actual evolution of the franchise
a new engine would be good for bungie. it could be like what the unreal engine was for alot of games.
a new engine huh? i could look into this
So what bungie is saying that there are slight changes done to Halo: Reach from the past halo games?
I’m a little interested now.
A new engine hmmm. Now all we need is a new story to use that isn’t just annoying.
and so the rant of kreyg continues. saw the vid when u was playing BOGT and just suddenly stopt cause u wanna prove Halo:Reach trailer wasnt ingame
naa, it was the Halo 3 reveal trailer from back when the first announced Halo 3. haha
damnit XD forget what i just said
Ahh, glad to see them using a new engine, maybe they’ll put the passion back in. Than again I have yet to see said trailer, or know any info for the game for that matter.