Offset - Being Silly!

[FindAPath]

I think AutoCAD is being silly, and must want a smoke break or something.

 

I have been creating demonstrative drawings to show paths along seat-belt-buckles for the past three days. I'm about 150 drawings in. Each of these paths is created by an Excel Macro that imports a Spline into Autocad. The path is the path that is done by the center of our 0.496mm Radius measuring ball.

 

We then have to offset this path by the radius of the ball to get a good approximation of what the actual surface looks like.

 

However, after about 150 times of offsetting these splines, AutoCAD doesn't want to do it anymore. It refuses to offset ANY object. What the heck is going on with it? I've tried rebooting the computer, I've restared Acad. It's starting to annoy me.

 

*Smacks AutoCAD upside the head* Get your stuff together and do what I need you to do!

[FindAPath]

Ok...

 

It'll offset darn near ANY object, and it will do ANY command to this particular Spline. But it won't offset it.

 

Help says I can offset splines, but I try to offset I get "Cannot offset that object." LAME!

 

Here's a screen shot of the spline. There's nothing intersecting it. It's ONE piece. There's like 150+ location points along it though. It was created using survey points and an excel macro. All of the other splines I've created this way have been offset-able, so to speak.

 

[pennylove]

Sometimes offset won't work on polylines that are small and the offset will eliminate all or part of the pline. It could be the same principal with the spline, and if that is what's going on here, there isn't really anything that you can do. The offset for the object just may be too large for it to offset. The way to tell if this is the case or not would be to offset in both directions, if it works one way, but not the other, then at least you know what the problem is. Sorry i can't be more help.

[CarlB]

Is it a SPLINE object or a spline-fit polyline? if a polyline, try PEDIT DECURVE then offset it then spline-fit it.

 

Something that can cause problems is if coordinates for objects are large such as over 1,000,000 for the x or y values. If so try offsetting the same spline after moving it nearer to 0,0.

[FindAPath]

The coordinates for it are less than 100.

 

It is a single spline object, not a patched together group of spline objects. PEDIT won't work on it, since it's a spline.

 

All of the other splines that I have offset have been about the same dimensions as this one, and have offset without a problem.

 

I need this to be done by 8AM to ship off for a trial tomorrow. If it can't be done using the offset command, is there some manual way to do it? I'll work all night at it if I have to...

[pennylove]

did you try exploding the spline? does it have to be a spline?

[FindAPath]

A spline allows it to have curves. The spline is a representation of a surface. A p-line doesn't have the required resolution that a Spline does.

 

You cannot explode a spline as it is a single element object, yes I've tried.

[CarlB]

How about converting the spline to a polyline, which has been discussed on this site before. A polyline with arcs, or a splie-fit polyline can look curvy enough.

 

One way to convert is by using FLATTEN on it.

[FindAPath]

I think I figured out what the problem is.

 

There are only 2 splines (out of hundreds) that AutoCAD hasn't been able to offset to the inside of the spline, but it can offset it just fine to the outside.

 

I consulted with one of the other AutoCAD guys here at work and he thinks that the problem may be that there are a couple of little sharp ticks in the spline which Acad is having a hard time dealing with when it has to reduce the spline.

 

Now, I just have to figure out where they are, and what to do about them.

[India]

Me too have experienced this problem and found whenever a splines inner radius is less than the proposed offset distance, ineffect the spline can not be created. It's not only splines but simple arcs too follow this principle. For eg. an arc with a radius of 5 can't be offsetted to a distance of 10 units. Since Splines are more complex entity and have many arcs both ways, all the arcs has to be in perfectly within the tolerance limit of offset distance.

In that case, you can try to reduce the offset distance to be within the smallest arc of the spline-set and try. Even Polylines don't offset sometimes!

[FindAPath]

That's the problem though. I cannot reduce the offset distance, because these drawings are for a court trial.

[Ako]

Will offsetting it half the distance and then offsetting the offset the same again work?

 

Dave

[FindAPath]

Nope...tried that, too. LOL

 

What I ended up doing was breaking it up into a whole truck-load of little mini-splines and offsetting each little piece and then stitching them back together. It took a long time but it worked out OK.

[bone]

Nope...tried that, too. LOL

 

What I ended up doing was breaking it up into a whole truck-load of little mini-splines and offsetting each little piece and then stitching them back together. It took a long time but it worked out OK.

 

Pretty damn impressed.

 

But did you meet the deadline?

 

Bone

[ASign]

Hi, CarlB!

 

 

How do OFFSET in ACAD 2k, despite 'coordinates > 10^6 for x or y values' & without 'move-OFFSET-move back'?

 

I spent 2 days trying OFFSET a p-line (closed or not) that describes 1 area & unsuccessful till now. Despite only 321 vertex, I guessed the big irregularity of area blocked OFFSET:

 

ACAD 2k error from OFFSET

--------------------------------------------------

Command: _offset

Specify offset distance or [Through] : 1 ' meters

Select object to offset or : ' Try 1: polyline (closed)

Specify point on side to offset: ' Try 1: outside (I need)

CANNOT OFFSET THAT OBJECT. ' Try 1:

Select object to offset or : ' Try 2: polyline (closed)

Specify point on side to offset: ' Try 2: inside (only test)

CANNOT OFFSET THAT OBJECT. ' Try 2:

Select object to offset or : *Cancel* ' Arrrhhh!

--------------------------------------------------

 

In a GOOD GIS FORUM (http://forums.esri.com/Thread.asp?c=3&f=38&t=278117) I detailed my problem & posted '2 STEP BUFFER' solution. But the result varies if buffer sequence is out-in or in-out & this variation raise with OBJECT IRREGULARITY. Despite '1 step buffer' is better & my idiot '2 step buffer' doesn't serves me, it works & maybe can be useful for REGULAR OBJECTS.

 

Something that can cause problems is if coordinates for objects are large such as over 1,000,000 for the x or y values. If so try offsetting the same spline after moving it nearer to 0,0.

 

I was WRONG, u r RIGHT & solved my problem: 'coordinates > 10^6 for x or y values', instead 'big irregularity of area' as I guessed. As my values ~ 7 x 10^6, I did you said: move p-line near to (0; 0), OFFSET, move back.

 

 

Tks,

 

Alisson.