We explored 3d in a new way which was perspective. Perspective is the 2d representation of 3d objects, how they appear to us in real can be drawn with this technique, we learned to sketch the interior spaces relatively to how they seemed to us. It is a relative quantity based on the distance of you and the object and also on the height of the vision. Horizon line is the height of the eyesight. When we look at the opposite edges of the object, it seems to merge at a point, when extended to a long distance. So the point where the meet is called vanishing point. Drawing is more about visual representation, so this is what we learned represented through sketches. You can have a short glimpse of what I want to say
virtually true 