39. Comprehensive line drawing

Considering that a straight line in space can be determined by the position of its two points, to construct it in the drawing, it is enough to carry out a comprehensive drawing of these two points, and then connect the similar projections of the points with straight lines. In this case, we obtain, respectively, the horizontal and frontal projections of the line.

In fig. 69, and the straight line l and the points A and B belonging to it are shown . To construct the frontal projection of the straight line l _{2, it is} enough to construct the frontal projections of the points А ₂ and В ₂ and connect them with a straight line. A horizontal projection is constructed in a similar way, passing through the horizontal projections of А ₁ and В ₁ points . After combining the plane P ₁ with the plane P _2, we obtain a two-projection complex drawing of a straight line l (Fig. 69, b).

A profile projection of a straight line can be constructed using profile projections of points A and B. In addition, a profile projection of a straight line can be constructed using the difference of the distances of its two points to the frontal plane of the projections, i.e. the difference of the depths of the points (Fig. 69, c). In this case, there is no need to plot the axes of the projections on the drawing. This method is more accurate and is used in the practice of technical drawings.