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I Have drawn some retaining walls as polygons. The client has changed their mind from rock clad, block walls to random rock walls. I want to increase the wall thickness from 250mm to 500mm. How would I do this? I have tried the offset tool. However it offsets it in both directions. Kind of works. However I then have to reshape one side back.

 

I haven't used the wall tool yet. Still learning.

 

Thanks.

Capture.PNG

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You could decompose the polygon and then offset the internal polylines by the correct amount and then re-compose the polygon. I think the better way though would be the following:

  1. use the "inner boundary" mode of the polygon tool to fill the internal areas. 
  2. offset the by the required amount.
  3. use the "inner boundary" again to fill the area in between the original wall and the new offset shape.
  4. use the add surface command.
  5. Delete the offset shape.

Screen Shot 2018-01-09 at 08.26.41.png

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11 hours ago, markdd said:

You could decompose the polygon and then offset the internal polylines by the correct amount and then re-compose the polygon. I think the better way though would be the following:

  1. use the "inner boundary" mode of the polygon tool to fill the internal areas. 
  2. offset the by the required amount.
  3. use the "inner boundary" again to fill the area in between the original wall and the new offset shape.
  4. use the add surface command.
  5. Delete the offset shape.

^ Mark's suggestion is a good one. I often do something similar.

 

If you're only wanting to reshape the inner area of a clipped polygon though (like Mark's image), the easiest would be to edit the clipped polygon using Modify>Edit Polyline and offset the polyline that defines the clipping area.

 

Kevin

 

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Decomposing breaks the object into all of their component parts. What you need to do now is:

  1. select just the objects that need to be moved inwards in your case,
  2. compose them again to make them a continuous polyline
  3. run the offset tool as required
  4. re-compose the all object to make a closed polygon again.
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9 hours ago, BJRobinson said:

Thanks Guys

I appreciate your replies.

I decomposed one of the polygons. See first Pic.

When I try to select the curved line, it just selects a small section. See second Pic. It always does this. So where to from here? Draw a new polyline over the old and offset it?

 

Capture1.PNG

How were the shapes drawn originally? When you select the original shape is it shown as a polygon or polyline in the OIP? There are two different things that could be happening. If its a polygon then the curves have probably been segmented when they were converted as part of the polygon. The number of segments depends on the 2d Conversion preference. Alternate during decomposition the polyline curve was broken up into its component arc segments. It looks like that is what happened here.

 

Personally I would draw a new arc or polyline over the old and offset it. I tend to use this approach because I like my geometry to have as few points as possible. You could also select all the small segments along that one curve and compose them. This would give you a new polyline you could offset. The result may have more points than it needs but depending on the complexity of the polyline this would probably be the fastest approach.

 

Kevin

 

 

 

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I chose to trace the internal line of the wall. Offset it by 250mm, then offset it by 500mm the other way. Then drew a line to join these at either end, Compose them, then converted to polygon. I was hoping that there would be a quicker way.

 

Thanks everyone for taking the time to reply. Cheers

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