cull among positive and negative offset

Am dealing with some offest problem and instead of trying to flip curve to obtain the right side of offset I was thinking to do both negative and positive offset, and then exclude the bigger in order to keep the one inside. I guess I have to use cull pattern, but I don't know how to link that with the area values of polilynes. Do I need a function?

has anyone faced a similar issue?

Thanks

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Permalink Reply by Danny Boyes on April 15, 2011 at 5:26am

Hi Stefano,

Are you still getting the problems after downloading the latest release v0.8.0009?

If you are then you can get the Culling results you want based on Length of curve as it's quicker to process than Area calculation. That way if you have many curves it will be significantly quicker.

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Permalink Reply by stefano suarez on April 15, 2011 at 6:12am

thanks Danny. Latest release seem to give the same resulta as previous. About your solution I'd have 2 question:

1- what component is the bothh sides offest?

2- my original polylines come from a planar surfac splitting. How do I extract the contour of each as a closed polilyne?

Thanks

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Permalink Reply by Danny Boyes on April 15, 2011 at 6:52am

1. The component is negative. I.e. x = offset distance therefore 2 inputs to D x and -x

2. Brep Edges > Join Curves

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Permalink Reply by stefano suarez on April 15, 2011 at 8:02am

ok, I got it but still weird behaviour happening. No all the polilynes are working.

Attachments:

offset curve.jpg, 250 KB

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Permalink Reply by Danny Boyes on April 15, 2011 at 8:20am

OK new approach! Based on the direction of control points, Clockwise or anti-clockwise this method will offset accordingly.

Notice on the bottom row, second from the right, the blue arrow and red arrows have a different order to all the others, but the line is still offset inwards.

Attachments:

OffsetWorkAround.ghx, 189 KB

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Permalink Reply by stefano suarez on April 15, 2011 at 9:59am

it works fine but only with straight lines. I'll make it work like this. Thanks again

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Permalink Reply by Danny Boyes on April 15, 2011 at 10:43am

It has to do with the polygon centre component. Change this to an average of the control points minus the duplicates

Attachments:

OffsetWorkAround_mk2.ghx, 202 KB

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Permalink Reply by stefano suarez on April 18, 2011 at 4:12am

your solutions are way out of my comprehension, chapeau.

But still it works only for some of the polylines. Wheter for example the previous one, if i introduce a list item component to offset the polyline one at time is working. could it be still buggy the offset component?

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Permalink Reply by Danny Boyes on April 18, 2011 at 4:38am

Yes I would say it is still buggy.

Permalink Reply by Danny Boyes on April 18, 2011 at 5:59am

I think you are going to have to simply use the Offset on Srf Component which be warned is much slower to calculate for GH and the more Offsets you have the slower it will be.

To give you an idea of how slow the example above was for 9 Curves = 9 seconds. 70 Curves took 70 seconds

Permalink Reply by flipchirps on January 20, 2012 at 4:17am

Hi Danny, Hi Stefano,

at the 'OffsetWorkAround' I substituted the PolygonCenterComponent with CurvePoint. Set it to 1/2 and it works. All your suggestions work fine.

I've got another one for the offset. Maybe it helps. See jpg.

One thing bugs me though at all solutions: If you have multiple intersecting curves formulating a small surface. The offset becomes larger than the surface edge. At a certain point the offset shows an error till you hit the self intersecting point. Than the offset starts over the surface edge.

How can I solve this problem? No more offset calculation after hitting the self intersecting point!? This is important for my next steps.

Thanks

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