What is parallel projection?

Parallel projection is also called parallel projection. One of the basic concepts of plane geometry, pointing out the corresponding relationship between line segments and points or line segments on a straight line. On the plane, suppose there are two straight lines A and B, and the straight line L intersects both of them. If any point A intersects with the straight line L and the straight line B intersects with the point B, the point B is called the parallel projection of point A on the straight line B along the direction parallel to the straight line L, which is called the parallel projection of B for short. The direction of the straight line l is called the projection direction. Let the parallel projection of the endpoint of line AA' on line A be BB' on line B, then line BB' is called the parallel projection of line AA'. When the straight line L in the projection direction is perpendicular to the straight line B, the parallel projection is called orthographic projection. [ 1]