system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:do artist have clear mental picture in their mind of the image they are drawing or they improvise on details?

I seen videos of artist drawing incredibly complex drawing within few minutes.how do they do that and i can i learn to do that??
gpt
On the subject of speed :

Most artists who can work quickly in the way you describe have practiced doing the same drawing, or same type of drawing at least, over and over again.  The are not necessarily good at drawing or even imagining any image, they're particularly good at *that* image and ones like it.  Animators, cartoonists, and caricature artists rely on this to make the volume of work they are required to produce even remotely possible.

Drawing something for the first time absolutely demands creativity, invention, and problem-solving, which are generally not things you can force -- they take time and energy and fail more often than they succeed.  Although a sidewalk artist might do a dozen drawings in an afternoon,  completing a dozen truly new or unique works of art in a single year is considered prolific.

On the subject of the mind's eye :

Every artist works differently.  Some have much clearer mental images than others, and some are much better at putting those images on paper (or other medium).  Generally-speaking, unless every step of a particular drawing has been memorized, there is a fair amount of interpretation and improvisation even in the case of the cartoonist or caricature artist.  Most artists are fickle and rarely marry themselves so closely to one idea that if something better comes along they will ignore it in favor of sticking to the plan.  In fact it's much more common when inspiration strikes for an artist to simply abandon whatever he was working on in favor of the new idea.