SetBulge question

[tagumz]

I know a -1 gives me a half circle. What is the relationship between this -1 and what I get in the finished arc?

[CarLB]

A reference I found says bulge=tan(angle/4), so for half a circle, angle is 180 degrees, bulge is 1. Don't know why the negative, maybe that is to specify direction? (I thought in AutoCAD all arcs are defined as being counterclockwise)

[csiarch]

This probably has absolutely nothing to do with what the OP is asking but there is discussion on bulge arcs in the Customization Topics on Advance Shape File Techniques. In these topics, there a formula for entering a bulge arc definition in shape font files (and shape files as well).

This one sez that bulge=(height/chord length)/254. Using this formula, the bulge value for 1/2 circular arc is 127. Height is the distance from the chord mid-point to the arc intersection. I believe this is a special variation because in programming font definitions, the largest number that can be used is 127.