How to Draw Intersecting Lines in Autocad

Extending Lines to Intersect

Joining two or more lines can be tedious and time-consuming if it is done manually and if there are many lines in your picture that need to be joined. Using the Extend Lines button on the CAD Toolbar (Classic view) or Extend Lines, in the Drawing Tools list, in the Picture group, on the Format tab (Ribbon view), you can easily extend single or multiple lines to an intersection point.

NOTE: You can intersect lines in configuration mode only.

There are two types of intersection points:

on-line                             off-line

Intersecting Lines to a Single Intersection Point

Each intersection of lines can involve only two lines whether the intersection point is on-line or off-line. If you select more than two lines, then more than one intersection point is involved and a separate operation for each intersection is required. For more information about intersecting multiple lines to multiple intersection points, see Intersecting Lines to Multiple Intersection Points.

Example 1: On-line intersection point

The following diagrams show an example of extending and intersecting a single line (line 1) with the intersection point located on another line (line 2). This is an example of an on-line intersection point.

Example 2: Off-line intersection points

The following diagrams show examples of extending and intersecting two lines (lines 1 and 2) with an intersection point that is not located on either source line (off-line). When the intersection point of two lines is found at a point off the two source lines, both lines are extended to the intersection point.

IMPORTANT: Lines may appear to be perfectly vertical or horizontal, but if they are even slightly off, they will extend well beyond the boundaries of your computer screen. In the following diagram, the "horizontal" lines were extended to the intersection points on the vertical line, but also extend to the right, past the edge of the viewing area on the computer screen.

For this reason, it is best to use the Make lines horizontal and/or Make lines vertical buttons on the CAD Toolbar (Classic View) or from the Format tab, in the Picture group, in the Drawing Tools list (Ribbon view) before extending lines to the intersection points. For more information, see Making Lines Horizontal or Vertical.

Intersecting Lines to Multiple Intersection Points

In cases where there is more than one potential intersection point, the closest intersection point is always used. However, an on-line intersection point always takes precedence over an off-line intersection point, regardless of it's proximity to the intersecting lines, and the number of lines and intersection points. The following diagrams show examples of these rules.

Example 1: No on-line intersection point

In the first example, the blue circle indicates the closest of the two intersection points, and because there is no on-line intersection point, only lines 2 and 3 are extended to the closest intersection point. Line 1 does not intersect with line 3.

Example 2: On-line and off-line intersection points

In this example, the blue circle indicates the on-line intersection point, and because on-line intersection points take precedence over off-line intersection points, line 3 is extended to the on-line point on line 1. Line 2 does not intersect with line 3.

Example 3: On-line and off-line intersection points

The following diagrams provide examples of extending multiple lines.

In the following example, lines 1 and 5 connect with the off-line intersection point (in the upper left corner), because there is no on-line point to take precedence. Line 4 goes through the off-line intersection points to connect with the on-line point on line 1 and lines 2 and 3 go through the off-line points to connect with the on-line intersection points on line 5.

In the next example, lines 1 and 6 connect with the off-line intersection point (in the upper left corner), because there is no on-line point to take precedence. Lines 2, 4, and 5 go through the off-line points to the on-line points on lines 6 and 1. Line 3 connects only with the first on-line intersection point on line 5.

The final example below, shows line 5 going through the off-line intersection points (red circles) to the on-line intersection point in the top left corner on line 1. Lines 3 and 4 intersect at the off-line point on the right because there is no on-line intersection point to take precedence. If you click the Extend Lines button again, lines 2 and 3 are extended to line 5 where on-line intersection points exist.

See Also

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How to Draw Intersecting Lines in Autocad

Source: https://www.ge.com/digital/documentation/ifix/version61/Subsystems/DRW/content/drw_extending_lines_to_intersect.htm

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