Expert: Scott Cook - 2/6/2004

Question
Aloha,
I have two questions:
1. How do you get AutoCad to draw a line tangent to a SPECIFIC point in a circle? E.g., I have a 28' circle intersected by a line and I need a line tangent to it running through the intersection of the line and the circle. I can figure out how to do it a long way around: make a line perpendicular to the existing line and MOVE it down to the intersection, but isn't there an easier way?

2. I draw elevations, details and floor plans for a glazing company. I am thinking of drawing 3D models of the storefront by extruding the floor plan and then taking the elevations from the model. Is this a good idea? Seems like it is a lot more work.

I can't figure out how to put a 'top' on the extruded tubes or how to draw the horizontal rails underneath the first rail I extrude. The floor plan shows a 1 3/4 X 4 1/2 inch tube connected by lines representing the horizontal rail which is also 1 3/4" thick. There are tubes under the first though... I.e., the frame has at the least a header and a sill.

I can send a simple drawing if you wish.

Thanks for your help. I have AutoCad 2002.

Aloha,
Jim
Honolulu, HI

Answer
1. Tangent is an angle 90 degrees off of the angle between the centerpoint of the circle and the intersection point.
So figure out the angle from the center to the intersection and add (or subtract) 90 degrees from it.
You can then start drawing your line from the intersection at the tangent angle for however far you want it to go. It's fairly simple to do in lisp.
2. It is more work. you will need some program to automate it for you, or forget it.