When I render 3D objects the prespective seems wrong. For example when viewing a cylinder from an angle, the end which is closer appears smaller than the end that is further away. What's going on?

I'm beginning a drawing with many line segments. Things are working as I expect until I add an infinite line across the drawing. However, once added, I can't select it and the snap to intersections tool doesn't recognize junctions between the infinite line and the other line segments. What am I doin...