Visual development can often lead down what ultimately become 'blind alleys'.
It's one thing to create a test shot of a girl on a swing. It may turn out looking fantastic. But the effort expended to do so has to be scalable. IOW, if you've made one representative shot ten-times more complex to do (as an example), the other 600+ shots in the movie are
each going to take that much longer to achieve, as a result. (meaning, in the fictional example, you're looking at a 6000% increase over a 'normal' CG feature pipeline; in time, money, artists .. possibly all three).
This 'painterly' look is the sort of thing which would work brilliantly for a short subject, or a main/end-title sequence. It
has been used on occasion, in tv commercials. For a feature-length film, it may be overly ambitious.
I don't doubt that
much effort was expended --over years! -- trying to come up with a process that might have made this 'look' viable on a feature-production scale .. but, once the release date was set, hard choices likely had to be made.
That's not to say that the envelope
hasn't been pushed by
Tangled's animation/dev team, though. The characters' expressiveness and the lush shading I've seen in the trailers show vast improvements over even
Bolt and
Meet the Robinsons .. and the environments, at least,
do have a somewhat 'painterly' look to them.
Plus, as has been mentioned by others, you can look at any individual still frame of Rapunzel or Flynn and recognize within it Glen Keane's
drawing style (which is pretty cool, IMO). Keane
is still the animation director on the movie, after all -- and obviously remains a tremendous influence.
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Development art and test sequences
always look more dynamic -- and often more interesting -- than the finished films for which they're created. A look at any "Art of" book or "Conceptual Test" DVD bonus feature will confirm that.
Visual development artists have the luxury of testing the waters, trying new/different things, etc. But when it comes time to
actually make the film, any new technique
has to work within a production pipeline, and toward a (often unwavering) deadline.