1, when the point is on the z axis, the two projections on the V plane and the W plane overlap, only the height; The projection on the h plane coincides with the coordinate origin o.

2. When the point is on the X-axis, the two projections on the H-plane and the V-plane coincide, with only the distance of X; The projection on the w plane coincides with the coordinate origin o.

3. When the point is on the Y-axis, the two projections on the H-plane and the W-plane coincide, with only the Y-distance; The projection on the v plane coincides with the coordinate origin o.

From the perspective of junior high school mathematics (see Chapter 29 Projection and View in the ninth grade electronic textbook of People's Education Network), generally speaking, when an object is irradiated by light, the shadow obtained on a certain plane (ground, wall, etc.). ) is called the projection of an object, the irradiated light is called the projection line, and the plane where the projection is located is called the projection plane.

Sometimes time is a set of parallel lights, such as sunlight or searchlights. The projection formed by parallel rays is a parallel projection. The projection formed by the same point (light emitted by a point light source) is called central projection. The projection produced by the projection line perpendicular to the projection plane is called orthographic projection. The projection that the projection line is not perpendicular to the projection plane is called oblique projection. The shape and size of the object projection are related to its position and angle relative to the projection plane.