I drawn some vector image in Illustrator for the animation. Imported to after effects, resized no matter the 'ai' file or layers that I imported from Illustrator, the images look really **** (loosing the quality of the image).
What can I do to resize the image without losing the image quality? Thank you!
This depends entirely on your illustration. If you have a bunch of 1 point or 1 pixel wide lines in the illustration then you have a problem resizing or moving the image even with CR turned on. Scaling down is a problem because there is no such thing as a half a pixel, and moving is problematic because the thin lines must line up with the pixel grid.
Most illustrations will resize to just fine, either up or down with CR turned on Provide that they do not have any Rastor effects like drop shadow or blur applied in Illustrator.