Copy and paste not as accurate as wblock?

[jpaulsen]

Ok after many years of using wblock, the newer users finally convinced me to use copy and paste instead. To be honest I like copy and paste in the newer versions because of all the options (paste to original coordinates, copy with base point, etc.)

But I just tried copying a centerline from a drawing and pasting to original coordinates in a new drawing. Now I can't join the entities into a polyline. They can be joined in the original drawing.

I used the wblock command to create a new drawing from the original entities. I can join the entities into a polyline in the new drawing created by wblock.

Has anyone else seen this behavior?

I see this behavior in 2006 and 2007.

I posted the drawing here if anyone wants to take a look at it.

[Mike.Perry]

Hi

Taking drawing file copy_and_paste.dwg from above post, I was able to reproduce the issue / problem...

* Open copy_and_paste.dwg

* Select the 6 Objects.

* Right-click -> Copy from pop-up menu OR use _.CopyClip command.

* New drawing.

* Right-click -> Paste to Original Coordinates from pop-up menu OR use _.PasteOrig

* _.PEdit -> _Join -> 0 segments added to polyline

The below procedure works at this end, give it a try...

* Open copy_and_paste.dwg

* Select the 6 Objects.

* Right-click -> Copy with Base Point from pop-up menu OR use _.CopyBase command ( Specify base point: 0,0 )

* New drawing.

* Right-click -> Paste to Original Coordinates from pop-up menu OR use _.PasteOrig OR Paste from pop-up menu OR _.PasteClip ( Specify insertion point: 0,0 )

* _.PEdit -> _Join -> 5 segments added to polyline

Have a good one, Mike

[jpaulsen]

Sorry it took so long to reply.

I tested this and it appears that copy with base point is more accurate than a plain copy or cut.

Thanks for looking into this Mike.

[Greywethr]

I read an article many moons ago that may be the source of your problem. When you use the AutoCAD copy commands, the accuracy is as high as it can get. However, when you use ctrl+c/x/v, you're using MS Windows commands, which are less accurate. If you do some searching, you may be able to find the exact discrepancy. I don't know if this helps, but knowledge is never useless. Good luck!

[irneb]

The issue with standard Copy-n-Paste (not the CopyBase command) is that AutoCAD calculates an automatic basepoint which is somewhere to the bottom left of the most bottom left entity. Or if you've zoomed in too far, then the bottom left of the visible screen.

This means the basepoint is now in a fractional format from all the lines' endpoints. And since AutoCAD only uses Double precision values to define XYZ coordinates - you'll always have some slight error when working with fractional distances. Now when you paste it into the new drawing - you end up with lines being ever so slightly off each other's endpoints.

For this reason I've told my people to NEVER use normal Copy-n-Paste, but rather Copy With Basepoint (Ctrl+Shift+C instead of Ctrl+C). Then choose one of the entities you're copying as a source for the basepoint. This way you get arround this problem by not having a random fractional value as the XYZ distances from the basepoint.