(1) The front view reflects the up, down, left and right positions of the object;
(2) The top view reflects the front, back, left and right positions of the object;
(3) The left view reflects the up, down, front and back positions of the object.
In the top view and left view, the side away from the main view is the front of the object, and the side near the main view is the back of the object. Because the distance between the projection map and the projection axis of the object does not affect the shape and size of the object itself, the projection axis can be omitted in the actual engineering drawing.
Extended data:
If the shape moves up, down, back, left and right in parallel, the position of the trilateral projection of the shape only changes on the projection plane, but its shape and size will not change, that is, the shape and size of the trilateral projection have nothing to do with the distance between the shape and the projection plane, that is, the distance between the projection axis.
Therefore, when drawing a three-sided projection map, the size of the projection plane (that is, the boundary line of the projection plane) and the projection axis are generally not drawn. As shown in the figure, in engineering, it is customary to call a projection a view, and the national standard stipulates that a V-plane projection is called a main view; H plane projection is called top view; W plane projection is called left view.
Baidu encyclopedia-three views