How did the shape of the theatres in Shakespeare's time affect the performances?

Answer 1

It isn't the shape of the theatres so much as the shape of the stages. Actors who have been trained to act on proscenium stages (the kind where only one side faces the audience) are trained to keep at least half of their faces toward the audience whenever speaking, because it is the only way to be seen, and because without electronic help, it's the only way to be heard. For a director to direct an actor to speak on a proscenium stage when he is facing upstage is extremely clumsy and incompetent.

On a thrust stage, the kind of three-sided stage that they had in Shakespeare's time, and which has come back in popularity in the late 20th century, however, an actor is faced with the fact that whenever he speaks, he has his back turned to someone. The trick is to keep moving so that you don't show your back to the same people all the time. It's a different acting style.

Another effect has to do with scenery. Proscenium stages allow you to have all kinds of scenery hiding in the wings and the flies. Because the view is essentially two-dimensional, extraordinarily complex set-pieces can be inserted behind the actors. This was the fashion throughout the eighteenth and nineteenth century. It was only in the twentieth with the advent of complex lighting that directors thought about creating sets with light rather than with wood and canvas.

On a thrust stage, however, complicated sets are impossible, for two reasons: first, there is noplace to conveniently store them where the audience cannot see them, and second, and most importantly, because the stage is three-dimensional, they get in the way of the audience's sight-lines, so the audience cannot see the actors.