When I choose Tool menu → Attach the resulting object isn't what I expected. Why?

Requirements

• PowerCADD version 9 (9.1.3 or newer recommended)
• Mac OS^? X (Mavericks version 10.9.2 or newer recommended)

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Background

To fully address this condition the history of the Tool menu → Attach is important.

What does Attach do? It allows you to you to physically join the end points of lines, arcs, béziers, and polygons to form a new, single object. The result of the operation can be a Polygon, a Bézier, or a Group depending on the settings of the menu item and the type of object geometry selected.

Originally (way back in PowerDraw 2 or 3? circa 1989ish?) Attach always yielded a polygon unless the selected path (objects to be attached) contained higher level geometry such as an arc or elliptical arc. In that case a Group was always created which traced the selected path with a new Polygon. In effect always keeping the higher level geometry. This made a lot of sense - and that's still the case today. Why? Because a higher level geometric object (e.g. an arc ) can always be converted to lower level geometry (e.g. lines or a polygon) -- but -- lower level geometry can never be converted to higher level geometry (e.g. we can't convert a polygon to a circle but we can convert a circle to a polygon). That's a critical distinction.

Starting in PowerCADD 8 and continuing into PowerCADD 9, we've been given a lot more control and the manual does a great job of describing those optional settings for Attach. There in effect three distinct optional settings for the Attach command and they are fully explained in the PowerCADD 9 PDF^? manual (choose Help menu → PowerCADD Manual and search for the term "attach" - page 252).

What To Do:

There are optional settings for the Attach menu item that let you control what the resulting geometry should be. As noted above they're described in the manual but in general:

Do This:

1. Hold the Option key and choose Tool menu
2. Observe: The menu display changes and Attach now appears at Attach... (note the three dots)
3. Move the mouse and release on the Attach... menu item and a dialog will appear giving you three choices.
4. Select the desired option and click on ok button
5. Select the objects to be attached
6. Choose Tool menu → Attach
7. Result: The selected objects are attached and converted as specified in 4 above

What's critical to understand is the distinction we outlined earlier about higher level and lower level geometry conversion and potentially destructive results. Remember that higher level geometry like an arc, or elliptical arc, have unique properties. For example an Arc is defined by a specific center point (defined by an XY position) and a radius, a starting arc angle, and an ending arc angle. Those are unique and geometrically advanced properties that let us do all kinds of other things such as dimension all those attributes.

Why is that important?

Well, imagine we were drawing a road center line - we need to be able to dimension that information to get it built. Unless we're building a drag strip, or a highway through Kansas, it's a pretty sure bet the road alignment will contain arc and tangent line geometry.

In the above dialog (optional settings that appears from step 3 described earlier), two of these conversion options destroy the advanced higher level arc geometry in our road example. Specifically the no conversion check box retains the high level geometry and gives us a new traced polygon with which we can do other things. (hint: read the manual for details: the traced polygon is part of a group with a pen pattern of nil which can easily be found and changed).

Why would we want that traced polygon? Well we can do all sorts of things like get a total road length with one click. Or use the polygon and then apply the Parallel Polygon menu item to create a filled version of the entire road alignment for renderings or cost analysis. There is a whole host of choices - but - we always have the real arc geometry to go back and dimension! Had we chosen to convert it all to a polygon or bézier curve we'd have no high level arc geometry left to dimension or edit - making more work for ourselves.

Summary

There is no single best choice for what optional settings to use for Attach. Rather, the fact we have the choices is what's critical as every drawing situation is different. Pick the one that's right for you - just remember the optional settings are remembered until you go back and change them.

We hope that helps
caddpower.com

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