What is a convention that Renaissance painters used?

Fillipo Brunelleschi's linear perspective revolutionized drawing and painting.

He was the first person to really nail down the rules of vanishing points and perspective grids.

Linear perspective is the practice of using a horizon line, vanishing points and grids drawn in perspective to portray things (especially buildings and cityscapes) in realistic proportions and to calculate feats of engineering.

This was a huge feature in Renaissance art.