Conventions used for lines

In orthographic projections, many times different types of lines may fall at the same regions. In such cases, the following rules for precedence of lines are to be followed:

• Visible lines take precedence over all other lines
• Hidden lines take precedence over center lines
• Center lines have lowest precedence

When  a visible line and a hidden line are to be drawn at the same area, It will be shown by the visible line only and no hidden line will be shown.  Similarly, in case of hidden line and centre line, onlu hidden line will be shown. In such case, the centre line will be shown  only if it is extending beyond the length of the hidden line.

Intersecting Lines in Orthographic Projections

The conventions used when different lines intersect is shown in figure - 6(a) & (b).

Figure 6(a):  The conventions practiced for intersection lines.

Figure 6(b):  The conventions practiced for intersection lines.