parallels

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debenriver
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parallels

Post by debenriver » Wed May 08, 2013 12:20 pm

Hi Eric

I hope you had a good walking holiday in Ireland!

One thing I have been meaning to ask for a long time.

When I draw a parallel to a polyline sometimes bits of the parallel line stay "stuck" to the original line. See attached jpg example. That is a 20mm parallel polyline.

If I do it in 1mm increments, 20 times, that doesn't happen, and the resulting final line is just as accurate, so it's not a big problem. Sometimes it is OK in 2mm increments.

I think this only happens when the polyline is made from rather small pieces, say 10-15mm or so long. At other times with a different polyline, the problem does not occur at all – in fact most of the time it doesn't happen.
parallels.jpg
parallels.jpg (5.63 KiB) Viewed 4822 times
Best - George

Eric Pousse
Posts: 730
Joined: Sat Dec 03, 2011 12:31 pm
Location: Tours - France

Re: parallels

Post by Eric Pousse » Thu May 09, 2013 9:16 am

Bonjour George
debenriver wrote: I hope you had a good walking holiday in Ireland!
Yes thank you, we have had sun and made very beautiful walks in Connemara and Burren.
debenriver wrote: When I draw a parallel to a polyline sometimes bits of the parallel line stay "stuck" to the original line. See attached jpg example. That is a 20mm parallel polyline.

If I do it in 1mm increments, 20 times, that doesn't happen, and the resulting final line is just as accurate, so it's not a big problem. Sometimes it is OK in 2mm increments.

I think this only happens when the polyline is made from rather small pieces, say 10-15mm or so long. At other times with a different polyline, the problem does not occur at all – in fact most of the time it doesn't happen.
Best - George
Yes George, in some cases, it is not possible to have parallel polygons.
Here is an example :
Image

The black polygon is the initial object with 2 small sides.
In blue, two parallel polygons at a distance lower than the smallest sides.
In red, two parallel polygons at a distance greater than the smallest sides.
The blue polygons are good.
The reds too (all red sides are at the requested distance from the original sides) but the result is not what we expect.
So careful when we do parallel objects at a distance greater than some sides of the original object.

But in your case, it is strange that the result is different between a 20mm parallel polygon and 20 times a 1mm parallel polygon.
Can you send to me this polygon in a .rcad file, please?

Cordialement.
Eric Pousse

debenriver
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Joined: Sat Dec 03, 2011 9:19 pm
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Re: parallels

Post by debenriver » Fri May 17, 2013 12:06 pm

Hi Eric
Can you send to me this polygon in a .rcad file, please?
I sent you a file some days ago. Did you get it?

Cheers - george

Eric Pousse
Posts: 730
Joined: Sat Dec 03, 2011 12:31 pm
Location: Tours - France

Re: parallels

Post by Eric Pousse » Sat May 18, 2013 6:57 pm

Bonjour George,

Yes I received it, sorry I have been very busy.

In your case, you have small sides and straight lines or almost straight lines which are segmented, this increases the errors.
By removing unnecessary points, it is a little better :
Image

Cordialement.
Eric Pousse

debenriver
Posts: 513
Joined: Sat Dec 03, 2011 9:19 pm
Location: Maine USA and Suffolk England
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Re: parallels

Post by debenriver » Sun May 19, 2013 9:45 pm

Hi Eric

No worries :D

I'll just go on doing it in 1mm or 2mm increments when I get a problem line – this seems to work perfectly out to any distance and it's quite quick to do.

Many thanks

George

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