vertex bulge - point on arc

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vertex bulge - point on arc

Postby Hakan » Thu Mar 20, 2014 3:17 pm

Hi,

After extracting vertex data from a dxf file I have the following information:
- 3D location point of the vertex
- a bulge

I have been spending alot of time to figure out how to construct the arc between vertices, I realized that I need atleast one point on the arc itself. I can't really figure out how to compute the point(s) even with the angle, sagitta formulas etc.

Can somebody help please?

/Hakan
Hakan
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Re: vertex bulge - point on arc

Postby andrew » Fri Mar 21, 2014 2:48 pm

The bulge is indeed the key to the puzzle.

From the DXF reference (http://www.autodesk.com/techpubs/autocad/dxf/reference/):

-> VERTEX
-> 42, bulge

"Bulge (optional; default is 0). The bulge is the tangent of one fourth the included angle for an arc segment, made negative if the arc goes clockwise from the start point to the endpoint. A bulge of 0 indicates a straight segment, and a bulge of 1 is a semicircle."
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Re: vertex bulge - point on arc

Postby Hakan » Sun Mar 23, 2014 6:12 pm

Thanks for the answer. I found an alternative solution, which is to 'explode' the vertices. Instead of having vertices I know have arc segments build of circle geometry, i.e. center point, radius, start- and end angle. There might be pros and cons with this solution, but it is suitable for my application.

/Hakan
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