Well, I do find it shocking. I understand many games use the same engines, but frequently you can tell from looking at them, "Oh, that's a Quake 3 game" or whatever.
I can tell from looking at it. The animations and especially Links facial animations (and head mvements, etc) are dead giveaways
Quake III games are easily distinguished because they all use use the so-called realistic art-style. Plus most of them were FPSs.
from the size of the characters to the look of the backgrounds to the fact that they have an enormous, realistic looking horse.
Textures, textures, textures (and models). It needn't have anything to do with the engine.
And yeah, changing the lighting as they have is pretty significant.
Not really. It is only significant from a visual perspective. I doubt it required many "drastic" changes to the engine. Cel-shading is just another type of lighting, the biggest difference between it and the more realistic lighting models is the way it "attenuates" over a surface.
All in all, I'd say a hell of a lot of work went into this game to the point where it doesn't look like Wind Waker at all
No doubt a lot(an enormous amount to be more accurate

) of work did go (and is going) into it. However, the change in graphics is almost entirely due to different textures and models not the engine. And I'll put money down on that.
The largest code changes are of course in the gameplay department, what with new elements like the horseback battling. I don't, however, consider such things to be part of the "engine" since generally they are much harder to re-use (unless all you're doing is slapping a new story and new areas onto the game)
I guess I should be more specific and say "the graphics engine".
They didn't just turn off the cel shading, you know.
Gee, really? eye guess eye 2 dumm to no that. :?
Look, I didn't mean to contradict you, and I certainly didn't mean to offend. I apologize if it seemed that way. I am sorry.