Space perception and (a bit of) direction perception. You see the world as it truly is. What is it that allows us to actively perceive depth and distance. Retina is 2d (up and down, side to side). 2d representation/input hits retina, but we have a 3d perception. Artists tried to represent the world (2d canvas) in paintings. 3d world on a 2d canvas: 1400s, 1500s, when we started painting 3d, leo divinci most famous in creating. 3 types of cues to 3 dimensionality: 1. When you look at something close up, your eyes have to come together to focus on that place in space (extra ocular muscles), an your lenses need to focus (by ciliary muscles). Opposite stuff (but same theme) when you"re looking far away. Cues of 1. accommodation (lens) and 2. convergence (eyes diverse when you look far away- spread our wider) This cannot happen for paintings because their 3d doesn"t actually vary in distance from you.