What Is an Orthographic Projection?

Orthographic projection means that the parallel projection lines are perpendicular to the projection plane. The projection produced by a projection line radiating from a point is called the central projection, and the projection produced by mutually parallel projection lines is called a parallel projection. The parallel projection line is inclined to the projection surface is called oblique projection. An object will produce a shadow under the illumination of light or sunlight, and the shadow has a certain geometric relationship with the shape of the object itself. This is a natural phenomenon. People abstract this natural phenomenon scientifically, and obtain the projection rule. Used in artistic and engineering graphics.

Orthographic projection means that the parallel projection lines are perpendicular to the projection plane. The projection produced by the projection line emitted by a point is called

An object will produce a shadow under the illumination of light or sunlight, and the shadow has a certain geometric relationship with the shape of the object itself. This is a natural phenomenon. People abstract this natural phenomenon scientifically, and obtain the projection rule. Used in artistic and engineering graphics.

1. People call the starting point of the light source the projection center;

2. The connection between the projection center and each point on the object is called the projection line;

3.The plane that receives the projection is called

Definition of mathematical orthographic:

In the body

Orthographic authenticity

Engineering drawings generally use orthographic projection. What are the characteristics of orthographic projection?

According to the projection method, we can see that when a straight line segment is parallel to the projection surface, the straight line segment forms a rectangle with its projection and the projection line passing through the two ends. Therefore, the projection of the straight line reflects the real length of the straight line. When the plane figure is parallel to the projection plane, it is not difficult to conclude that the plane figure and its projection are congruent figures, which reflect the real shape of the plane figure.

From this we can conclude that a straight line or a plane figure parallel to the projection plane, and the projection on the projection plane reflects the real length of the line segment or the solid shape of the plane figure. This projection characteristic is called authenticity .

Orthographic accumulation

Similarly, we also see that when a line is perpendicular to the projection plane, the projection lines passing through all points on the line coincide with the line itself, so there is only one intersection with the projection plane, that is, the projection of the line accumulates into one point. When the plane graphic is perpendicular to the projection plane, the projection lines passing through all points on the plane coincide with the plane itself, and intersect with the projection plane in a straight line, that is, the projection is a straight line. It follows that:

When straight or flat graphics are perpendicular to the projection plane, their projections on the projection plane accumulate into a point or a straight line. This projection characteristic is called accumulation .

Orthographic similarity

We also see that when a straight line is inclined to the projection surface, the projection of the straight line is still a straight line, but it does not reflect the real length; when a flat graphic is inclined to the projection surface, the projection on the projection surface is similar to the original shape. Note: Similar shapes are not similar shapes. They are the same as the original shape, but they have the same number of sides and similar shapes. The projection of the circle is ellipse. This projection characteristic is called similarity ^[2] .