criteria for Extrude Along Path scale options

[propstuff]

There isn't any information I can see in the manual for this, but I've concluded that the Scale options do not work if the Path has corner verticies. Fair enough.

My current problem is :

choose Arc by 3 points.

Draw an arc.

choose Arc by Tangent

from the end of the first arc start the second one and make it Tangential to the first, and curving back in the other direction to make an S shape.

Compose (or Combine/ Connect)the 2 arcs to make the Path object.

The result ought to be a smooth continuous curve and the Extrude Along Path -Scale option ought to work, but it doesn't. They're greyed out.

What are the criteria for getting the Scale function to work?

[G_Hannigan]

Nicholas,

You're right. It doesn't work for some reason. I couldn't get the simple, unscaled extrude to work from an S shape from two arcs either.

Strangely, this worked.

1. Create the two arcs forming the S shape.

2. Move one of the arcs vertically a tiny amount (I used 1/32"). Connect the two with a straight line.

3. Select the two arcs & the straight line, compose.

It will now work as a path & scale options are available.

My guess is that the two arcs alone create a problem where they meet, even though they are created tangent to each other.

George

[islandmon]

Paths are very susceptible to vertex stacking. A similar issue exists with Revolve Around Rail... the procedure often fails for wont of a single fractal of space between the profile & the axis of rotation.

[alanmac]

Works for me in 10.5 on a Windows XP if I'm doing as you describe.

Draw two arcs, one touching the other to look like letter S, combine to make one S shape. Draw a circle, select both items and extrude along a path choosing S shape as path.

Am I reading your problem right?

I'll email you file.

Alan

[ 03-28-2006, 11:43 AM: Message edited by: alanmac ]

[G_Hannigan]

As EJ says, it doesn't always work and the scale function is grayed out for some reason.

12.0.1 - Win XP Pro

George

[propstuff]

Hi Alan

I got your file, it is what I'm trying to do.

Your file works at this end.

Unfortunately this was yet another example of me demonstrating a function to a group of Design students and it worked ok. Then they did the same task and neither they nor I could get it to work again.

Note;

For a composed path made of 2 arcs that won't work, if I delete the vertex at their joining point, the Scale option will work, but the arcs get distorted in the process and are no longer the path I want. Not much help there.

Can someone at NNA define what criteria have to be met for this to work reliably?

[ 03-28-2006, 03:09 PM: Message edited by: propstuff ]

[Biplab]

The criteria is simple - g1 continuity (tangency). If the path is g1 discontinuous, scale option is grayed out. I think when drawing the arcs one needs to make sure that the tangency constraint is what s/he is getting.

[propstuff]

Hi Biplab,

I was relying on the Snap Constraints and Cursor cues for the 3rd mode of the arc tool to ensure Tangency.

To begin the second (tangential) arc, the Cursor indicated the end of the first Arc, for the second point it indicated "Tangent". I thought that would do it.

[Biplab]

I am using the same procedure that you are - and I am having no problems at all. The two factors that may affect the procedure (although not likely) is the snap radius and 2d conversion resolution. What are these settings for you?

[alanmac]

Just to add another twist to this ....

When I first did this I drew an arc, then duplicated it, flipped the duplicate and moved it over to touch the other arc to make the "S" shape. When I hit compose one arc jumped and it created a circle from the two halves !!!

Figure that one out....

Alan