AutoCAD Tips to Work Smarter - April 2003

Finding the Midpoint between Two Points

The 'cal command in AutoCAD can be used to perform typical arithmetic operations as well as geometry and point functions.

The mee function is designed to locate the midpoint between two endpoints. This is handy when trying to locate the middle of a rectangle. Here is how you would use the mee function to draw a circle in the middle of a rectangle.

1. Select the Circle command.
2. When prompted Specify center point for circle or [3P/2P/Ttr (tan tan radius)]:, type 'cal and press ENTER.
3. When prompted Expression:, type mee and press ENTER.
4. At the >> Select one endpoint for MEE: prompt, left-click at one corner of the rectangle (Point 1 in the figure at the right).
5. At the >> Select another endpoint for MEE: prompt, left-click at opposite corner of the rectangle (Point 2 in the figure at the right).

Hint: If you use the mee function frequently, consider creating a custom toolbar button to automate the task. Don't know how to create a toolbar button? Check out the Creating a User Defined Toolbar Button tip.

Finding Other Midpoints

That's great, but what if you want to locate the midpoint between two intersections or two center points or even the midpoint between an intersection and a center point. The 'cal command supports these options, but in a different manner.
The midpoint between any two points is equal to adding the X, Y and Z values of the two points and dividing by 2. The 'cal command supports arithmetic functions applied to points. The following expressions are supported by 'cal:

(int+int)/2 -- The midpoint between two intersections
(cen+cen)/2 -- The midpoint between two center points
(int+cen)/2-- The midpoint between an intersection and center point.

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