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Exporting dwg - curves and poliline problem


Ewaryst

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 @Ewaryst  - Common technique is to replace vwx polylines with arcs.  If the original poly is not circular, then trace with the arc tool to compose a series of arcs to approximate.  It might be useful to make a copy file for use only as dwg export. It gets a bit dodgy syncing the two files if there are lots of edits or revisions to the project file, but copy/paste can work fairly efficiently if layers and classes are handled well.

 

I think dwg always breaks vwx polylines into segments. I think the vwx preference for 2d conversion controls the segment length. Higer conversion resolution means shorter segments in the export.

 

hth

 

-B

Edited by Benson Shaw
trace
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@Ewaryst you may want to check the following three things in AutoCAD:

 

1. VIEWRES variable - it controls the smoothness of circles,arcs and polylines/splines or any line with curves. The default is set to 100 which is on the low side and creates the effect you see with the arc. Setting it to 2000 should give a better result that is sufficient in most cases. If needed set it higher.

 

2. the LTSCALE variable - depending on units and linetype definition the LTSCALE may cause dashes etc. to be strechted or compressed too much to the extent that it looks like a continuous line. Changing the LTSCALE value to a larger or smaller value may solve this. This may not always be causing the issue with the dashed polyline though and then you may want to check as per point 3 below, especially if some dashed etc. polylines start to look like they should and others still not.

 

3. The linetype mode of the polylines. Use PEDIT (Polyline EDIT) and select all polylines, then select the linetype mode option and set it to continous. That way it will ignore the lengths of the vertices and make the linetype look as if there are no vertices. If (some of) the vertices are too short a non-continuous linetype may look like a contintous linetype for the entire polyline or for parts of the polyine. Setting the linetypemode to continuous should solve this.

 

An additional comment regarding point 2.... sometimes there are multiple linetype defintions in a drawing that require the LTSCALE to be larger than 1 for some of them and smaller than 1 for some others. E.g. when combining (parts of) multiple drawings in a single drawing. Then you can only solve the problem by reloading the linetypes from your local set of linetypes so that they all react the same to the LTSCALE variable value.

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2 hours ago, Benson Shaw said:

I think dwg always breaks vwx polylines into segments. I think the vwx preference for 2d conversion controls the segment length. Higer conversion resolution means shorter segments in the export. 

Yes and no. The 2D conversion resolution usually affects just the display and not the actual vertices of the polylines. I've never noticed that setting the conversion resolution to hight to affect the actual polyline segments. It might affect the segments of splines if they are changed to polylines for whatever reason.

 

The issue with the arc is pointing towards the VIEWRES variable having a low value and this can also affect the appearance of the polyline smoothness.

 

For non-continuous linetypes for polylines it depends on the linetype scale factor and the linetype mode setting to have continous on/off that gets applied in the DWG based program whether dashes etc. show up properly. Unfortunately there is no linetype scale factor setting for export of dwg files, only for import of dwg files.

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@Benson Shaw Thanks for the kind words, I'll try to keep it coming.

 

In the nearby future I hope to add a little bit of Solidworks experience (never worked with that before) as I get to work with that for a few weeks. Maybe it will provide for some wish list items (or not, if I think the VW way of doing things is better). I'm curious to see how it will compare to Onshape, though I didn't get to really dabble with that recently other than have a look at a model in it.

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There is a setting in Acad options for the display of arc and line segments. If this setting is too low, you might see segments. Unfortunately I don't remember by heart where it is.

 

Another thing to check is to zoom closer and  type "regen" - the segments might go away. Assuming you have access to Acad.

 

Acad does a lot of display performance optimizing and sometimes needs to be "told" to improve the apparance. This is to say your file may actually be ok, even if it appears segmented at first glance.

 

I  general, for us the vw dwg export seems to work fine when it comes to appearance.

 

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