snapping tangent to arcs

[Outlander]

Is there any way to draw an arc and snap tangent to another arc or circle; the snap to tangent function seems to work only when there is an arc and a line coming together, but not with 2 arcs. It's very frustrating and impossible to draft accurately.

[Jonathan Pickup]

which version of Vectorworks do you have?

[Jonathan Pickup]

i can snap one arc to another and get the tangent, but it is not easy. It depends on the arc mode you choose and you have to finish on the first arc for it to work.

A really easy method is to use the fillet tool. you can draw 2 arcs and place a fillet between then, and its really fast, and reliable.

[bcd]

But it should be easy. I cannot draw two circles tangentially to each other without first defining their collinear radii. (shouldn't the Smart Cursor >Object Snap Settings>Nearest Point on edge acquire this point for us?)

Even the Tangent Constraint will not find the tangent point for two arcs but finds the tangent point of one arc and the generating radius of the 2nd arc ; useful sometimes but not what's being asked.

(try this:

Draw a circle 1m radius.

4m away center and draw a second circle such that it is tangent to the first.

Why is this so hard in VW?)

[MullinRJ]

I was able to create arcs tangential to other arcs easily by 1) setting the Tangent Constraint ON (R key), and 2) using the third Arc drawing mode (Arc by Tangent) for the second arc. You can draw the first arc any way you like.

After you finish drawing the second arc, adjust the start/end point of the first arc to coincide with the second arc and the two curves will look as one.

If you need to make two existing arcs with fixed centers, tangential by adjusting the radius of one or both, then draw a line between their centers. The tangential point of two arcs will always be on that line. Adjust a radius, or both radii, to a point on that line then adjust the start/end points on your arc(s) to that point. They will then be tangential to each other.

HTH,

Raymond

[bcd]

Yes. But what a rigamarole !

[Jonathan Pickup]

Sometimes you have to know how to set out the geometry so you can draw correctly. Sometimes Vectorworks doesn't to it all for you.

[Outlander]

I am a little concerned here, some of you are saying that you CAN turn your tangent constraint on and snap an arc tangent to another. I definetely can not do this, actually a snap does appear on the arc but it is in a location that is obviously not correct. I am using VW 2010, so I'm not sure why it's not working for me. Also, I'm not interested in doing geometry for every single arc I draw, the snap tools should be saving me time, and really, it's a very basic operation for a CAD program to offer.

[bcd]

Sometimes you have to know how to set out the geometry so you can draw correctly. Sometimes Vectorworks doesn't to it all for you.

Yes, I'm not suggesting I need geometry lessons, rather what you would imagine to be an easy construct for VW turns out to be a process where you do have to 'set out the geometry', Fair?

[mike m oz]

(try this:

Draw a circle 1m radius.

4m away center and draw a second circle such that it is tangent to the first.

Why is this so hard in VW?)

Its actually very easy if you turn on the Object snap for Nearest Point on Edge and use the first mode for drawing the circle (or arc). As you draw the second circle (or arc) close to the first circle (or arc) the snap point will show up. As Raymond pointed out the tangent point lies on the line connecting the centres so you will also see this temporary snap line on the screen (see images below).

[bcd]

Yes, this is exactly what I expect. Except I get the Perpendicular Smart Cursor Cue is missing.

Wait. I finally got the expected result - bizarrely by:

Turning the Snap to Angle constraint on and off and

Deleting all the prescribed angles.

Now with the angles re-entered it still works. (in my above exercise NPON was turned on)

[mike m oz]

bcd, you can get either snap to appear by moving the 2D cursor around very slightly (see images below). Therefore you don't need to turn your Angle snap off - if it makes it easier for you then that Snap can be toggled on and off with the 'S' key.

[bcd]

Thanks again Mike. I know how they work. I'm saying something was glitched in that it wouldn't work until I performed the 'reset' above. Now it works as expected; beautifully (but only with the Angle Snap On with or without preset Snap Angles)

If others are experiencing the disappearance of their 'perpendicular' Smart Cue try this reset: it worked for me.

thanks for your persistence - solved.

With regard to the OP and snap settings - wouldn't it be nice if the Tangent snap mode acquired the tangent snap point of two arcs rather than the tangent point the first arc and the final generation line of the second arc?

[bcd]

I feel like I'm either missing something completely here or really over-thinking it. But can someone please explain how I can move a line to be tangent to a circle, without generating a normal?

Thanks

Edit - found it.

This time the Align Edge Snap needs to be on (not the tangent snap)

And the Object Snap Center.

Move the line to the center point - pick up center point as smart point.

Then move along the normal to Align edge & place on Object/Align Edge snap point)

Edited November 14, 2009 by bcd