Question

For which purpose did some Renaissance artists use corpses?

Answer 1

Church restrictions on bodies: it was sinful for a person to be without clothing in front of an artist. To create realistic paintings, corpses were used. 

Corpses were used as a model for the human body. Renaissance painters strove for realism and the corpse provided a realistic human image. An alive person would not be able to pose, in particular without clothing, for a painter. This would have been sinful.