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One-time snaps - correct behaviour
Does anyone know the correct behaviour (or at least what AutoCAD does) when the user sets a one-time snap (snap override) and then a point of the required type is not found? i.e. does it generate an error and re-prompt for the point or does it simply accept the point at the cursor without complaint.
e.g.
Type LINE to start a line command
Select any point to start the line
Type END to set the one-time snap to ENDPOINT
Select a point not on any object
Should it display an error “No endpoint found for given point” and re-prompt for the point, or should it just accept the point clicked.
Not generating an error when the user has explicitly set a one-time snap seems to be a bug, since just returning the point clicked won’t be exactly at the end of an object – if the user just manages to miss the end of an object then not generating an error will result in a point being near but not exactly on the end. I can see that running snaps shouldn’t generate a error in this case but a one-time snap probably should.
Different flavours of icad seem to handle this differently. What is correct? What does AutoCAD do?
Replies to This Discussion
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Permalink Reply by Randy Mahoney on -
Mark,
I can confirm that Cadopia Intellicad, both an older and newer version, behave just as you describe : the second pick of the line can be any location and no message is given about a missed point or entity. This can be very misleading when working in 3D. Regardless of the Z value of the start of the line, a point picked away from any entity acquires a Z value of zero on the XY plane of the UCS. More often than not, this is not what you want in a 3D model. I don't have Autocad to check, but I suspect it behaves the same way. For comparison, my old Cadkey 19 won't allow an arbitrary location for the second point of a line if any snap choice is made. If you pick away from a snap point, an 'Entity Not Found' message is displayed and you're left in the LINE routine until you pick a valid point or Escape out. You can chose CURSOR if you want pick just anywhere, and the Z value will be zero on the construction plane. Your question is a good one and I think an error message would be appropriate.
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Permalink Reply by Mark Dunmill on -
Strange, I just tested with some different versions of IntelliCAD and found that CADopia DOES generate an error if you set a one-time snap and then fail to get a point of that type. In fact I tested 2 versions of CADopia, 2 of Bricscad and 2 of progeCAD and found that only progeCAD doesn't generate an error when you use a one-time snap and don't select a point of the appropriate type.
Here's my results:
CADopia Standard 6 SP 2 [6.0.7.0]
: line
Start of line:
Angle/Length/: end
Snap to endpoint of:
No endpoint found for selected point.
CADopia 8 [6.4.23.0]
: line
ENTER to use last point/Follow/:
Angle/Length/: end
Snap to endpoint of:
No Endpoint found for specified point
Angle/Length/:
Bricscad Pro [7.1.0018]
: line
Start of line:
Angle/Length/: end
Snap to endpoint of:
No endpoint found for selected point.
Angle/Length/:
Bricscad Pro [10.2.3.16822]
: line
Start of line:
Angle/Length/Undo/: end
Snap to endpoint of:
No endpoint found for selected point.
ProgeCAD 2009 Standard [9.0.24.1]
Command : line
Start of line:
Angle/Length/: end
Snap to endpoint of:
Angle/Length/Follow/Undo/:
ProgeCAD 2010 Professional [10.0.2.8]
Command : line
Start of line:
Angle/Length/: end
Snap to endpoint of:
Angle/Length/Follow/Undo/:
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Permalink Reply by Randy Mahoney on
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Well, I dunno. I guess it's nice to know that some of the developers have noticed this. My old version is Cadopia Std 4. My newer version is not, strictly speaking, Intellicad. It's the DWG editor supplied with Solidworks. I know that it's a Cadopia version - they get credit in the About dialog. I have the editors for SW 2009 and 2010. They look like Cadopia version 8 to me. Last fall I downloaded a trial of Cadopia 8 just to check it out. So some have it and some don't and we still don't know about AutoCAD. It's good to know Bricscad shows the message. That will be my next CAD software when they release the Linux version. Soon I hope.
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