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I have mentioned this problem before on the forums and also had a dialogue with UK tech support within the last couple of years (they were nice but had no answers)  but with the introduction of new truss objects I thought I would raise the issue again. 

 

The zig-zag lacing on bundled VWX truss objects is looks smooth. When I try and do something similar by extruding a circle along a poly line I get a really jagged mess of geometry which I cannot for the life of me eradicate. 

 

1. Does anybody see this anomaly?

2. Do you have a workaround?

3. How do VWX make their truss lacing so smooth? (They are generic solids so I have no way of knowing how they are made)

 

I have enclosed the file in case anybody wants to experiment.

 

Many thanks

 

5a27f5157427f_ScreenShot2017-12-06at13_47_45.thumb.png.bd61a1d771edfdb281724798ec664e29.png

Truss_Lacing.vwx

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From looking at your screen I would think the VWX truss lacing is made with a curve split in many parts, while you have a continous curve.

It could also be the weight of your nurbs points make it look so rounded.

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7 minutes ago, Hippocode said:

VWX truss lacing is made with a curve split in many parts

Yes, I wondered about that but couldn't manage to make two abutting extrude along path objects into a solid addition, so can't understand how the whole length is a generic solid. The Polyline shown is the path object I extruded along.

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@markdd I took a look at your file and I tried to create the extrude along path using your poly line and had identical results.  I then tried to recreate your poly line using corner vertex points instead of arcs and when I did an extrude along path the result was nearly identical to the VWX truss lacing.  

 

I know that when I create truss libraries for VWX I use extrude along path for all of the lacing and perform a solid addition to marry the lacing to the chords.  Sometimes it does take some fiddling to get all of the extrudes to combine to one solid addition but usually it is one extrude that is causing the issue and copying an identical extrude from another portion of the truss and pasting it in place solves the issue.

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Thanks Justin

 

I couldn't believe that I couldn't add to EAP objects together so tried again and it worked fine. I can't manage YET to make a path object work like the lacing in your truss libraries. Using the Arc Vertex Fillet mode of the poly line tool gives the same results that I saw before. Which mode did you use?

 

Many thanks

 

 

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I am glad that you were able to get EAP to work.  When I drew your poly line I used the corner vertex mode and drew straight lines from arc end point to arc end point using the snapping to make sure I was drawing using the correct vertices.  I have attached the file showing my poly line which I drew using your original poly line and my resulting EAP in red.  I hope this helps.

 

Justin

Truss_Lacing.vwx

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Thanks Justin 

 

I understand this. How did you therefore manage to achieve the filleted corners of your VWX truss lacing without them looking such a jagged mess!?

 

Thanks

 

Mark

Edited by markdd

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Here's how I would approach it given the issue with the EAP conversion of the polyline. The base line could be a polyline or a NURBS curve. Both will fillet. -

 

5a2817ab92d44_ScreenShot2017-12-06at8_14_59AM.thumb.png.9c1fcf844cf1cb64766a2802fa8bbcd6.png

 

Justin's example is not quite the same since it doesn't reproduce the fillets.

 

All of this is game is definitely a workaround. I would say there is a bug in the NURBS conversion process which is making unfriendly paths. If you take a nice clean polyline with filleted corners and convert it to a NURBS curve, the problem is immediately apparent. Since the EAP converts the path to NURBS automatically, the symptom is transferred to the EAP result. @JustinVHare you going to submit this or should Mark and I both submit it?

 

Kevin

 

Truss_Lacing_KM.vwx

Edited by Kevin McAllister

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Hi Kevin,

 

Your example is a nice result and is a much better reproduction of the original object.  Why don't you and Mark take care of submitting the bug as the two of you discovered the issue as well as the workaround solution.

 

Justin

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I posted this as a bug about 18months ago and it was acknowledged as a problem. I will bug submit again.

 

@JustinVHwhat approach did you take with your truss lacing?

 

Many thanks

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@markddI did not create the truss symbol that you used in your file so I cannot say what technique was used unfortunately.  I know that when I do make truss I like to use a traditional extrude for each piece and rotate into place as I feel I do have a bit more control.  Once I am comfortable with the placement of a single piece of lacing I use alt+click to duplicate the piece and move it into place along the truss.  

 

I have not yet made the particular style of truss in your example as I have worked on traditional US box truss styles but I think I would still work in segments to get one component correct and duplicate and move as necessary until I can perform the solid addition.

 

Justin 

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After experimenting some more I'm wondering if maybe its a display issue with Wireframe. The anomalies seem to disappear when you render the geometry in OpenGL with the detail set to High. I'll still bug submit it.

 

Kevin

 

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Yes, I remember establishing it as some sort of display issue with Wireframe the last time. The EAP objects display perfectly well in OpenGL as well as Hidden Line and Renderworks styles. My main issue last time was that I wanted to display in Hidden Line without the various solid additions showing their joins  - which they still do.

 

Thanks Kevin

Edited by markdd

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3 minutes ago, markdd said:

My main issue last time was that I wanted to display in Hidden Line without the various solid additions showing their joins  - which they still do.

 

I would love that too. I think it means having an option to turn of the display of Isocurves which other programs like Rhino allow you to do.

 

Kevin

 

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@JimWthis is one of the threads I'm trying to bug submit for. Maybe it needs to be moved to Troubleshooting.

 

Here's my bug submission -

 

General Bug Description - Polyline with fillet corners creates an Extrude Along Path with anomalies.

Details - Note that I am running Mac OSX 10.13.1

1) Create a polyline with filleted corners.
2) Convert to a pipe like Extrude Along Path using the polyline as the path and a circle as the profile.
3) Note the results.

See this forum thread - https://forum.vectorworks.net/index.php?/topic/53515-extrude-along-path-issues/ - and the accompanying file for more information.

This may be a Wireframe rendering issue not a geometry issue.

 

I submitted the file to accompany it yesterday since that part of the submission system works. I've also included it here.

 

Thanks,

 

Kevin

EAP_Bug.vwx

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