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Tangency constraint

P Retondo


The existing tangency constraint does not enable us to draw an arc tangent to two other arcs. The math isn't too difficult - centers of adjacent tangent arcs must be colinear with the shared point of tangency. Could you add this capability to the tangency constraint?

This could work one of two ways: 1) with arc by tangent point selected, after you establish tangency with the first object, a tangent/tangent cue would appear at the correct point on the second object, or 2) it would work like the line tangent/tangent capability (click on one, click on tangent/tangent cue on the second).

AutoCAD has a pretty good tangency capability, whereby you can string together successively tangent arcs of different radii. If the arc-by-tangent mode could enable us to set the radius, we could have that capability as well. It seems to me to be more important to set the radius than to set whatever parameter "L" currently sets in that mode.

If you could extend these concepts to include splines, it would be even more powerful. I realize that with continuously-changing curvature there is a difficulty in attempting to calculate an infinite number of possible tangencies in real time . . .

[ 03-23-2003, 03:28 PM: Message edited by: P Retondo ]

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The fillet tool does this pretty well already with regard to arcs. Without it, it's pretty hard to draw, say, kidney shapes with every arc tangent to its neighbor. No luck with splines, though.

I've not been very encouraged by previous implementations of vw's tangent snaps/cues.

1) An entire release with NO tangent snaps enabled (9-9.5)

2) In vw9.5.3 tangent snaps are still dodgy. Stringing tangent curves together, the second line frequently won't show a tangent snap to the first line.

I'm reluctant to ask for something that builds on this foundation, unless vw10 is better about this (I'm not there yet...).

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Chad, you are correct in saying that the fillet tool works in some situations. However, the fillet tool will not draw a tangent to a given point, nor will it draw a convex curve in situations where that might be desired. The fillet tool requires that I specify the radius, which can require a manual calculation. My request is to have a more goemetrically powerful tool.

This capability would be particularly desirable for Civil Engineers laying out roads. In this discipline, and in many architectural situations as well, some control over start and/or end points for tangent arc fillets is important. At times it is also important to be able to create a string of tangent arcs, starting from given points with user control over radii.

[ 03-24-2003, 07:47 PM: Message edited by: P Retondo ]

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