Monday, March 9, 2009

The Mysteriously Moving Polyline

Since this is a repeat question in my office, I thought I would share the solution with you. Here are two possible scenarios:

1. Draw a polyline with an elevation of 0.00 in location "A". Highlight the polyline and change the elevation to 147.00 and the polyline moves to location "B".

2. Draw a line at any elevation and location "C". Highlight the line and change the elevation of one endpoint to a different elevation and the line moves to location "D".

You might even find that if you try to execute a move command on either the polyline or the line from Step 1 or Step 2, they won't appear to move because the elevation doesn't change.

Do you know what the problem is?

The view has been changed to something other than "Top".

To correct the situation, just type -view at the command prompt and then top to reset the view. You can also find the solution in the dropdown menus at View-3D Views-Top.


Anonymous said...

Hey - i tried this and did NOT get your expected result. Do you guys have a custom lisp or something helping the process that might be changing the view?

I can understand that the line is not coplanar and cannot be extended or trimmed unless you do the extend option or apparent intersection. Clue me in dude, not understanding "whats happening. "Yeah, i had Rerun in my head saying that to Rog...

TommieR said...

Rotate the view using 3d orbit. Only rotate it a bit, not a lot so that the drawing still looks like it's in the normal top view, but the view is actually rotated. That's why the ends of the lines appear to move to a different location.

Hope that helps to explain the original problem that required the solution described in this post.

Anonymous said...

It's not the view that's the problem, it's the UCS. Polyline property "elevation" is calculated with respect to the origin in 3D space ... the distance from point 0,0,0 to a perpendicular point on that polyline. So if you have a polyline with different Z elevations at start and end, then it is "living" on a different (tilted) plane from the rest of your polylines.