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Lee Coll

Loft Surface Rejection

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This is the first issue I've had using Loft Surface and considering the two NURBS shapes I'm trying to use to transform into a varying-section "elbow", I just can't figure out how to allow VW to accept the command, without de-selecting both items with nothing happening.  Both sections are NURBS that were converted from simple 2D shapes: the Circle is shown normal to the X-axis and the Oval (made from two circles and a rectangle, then joined as a single closed polyline) is normal to the Y-axis (Front).  So the planes where each NURBS entity exists are perpendicular to each other.  They are spaced to be transitioned to a curved exhaust segment, and I've used Loft Surface with No Rail (no effect) and created a Rail (that touched both edges - still no effect), and have yet to create the solid.  It just doesn't work and I've selected Create Solid (I will shell out later) with no result.  I must be missing something very simple here.

Screen Shot 2018-11-04 at 7.32.58 PM.png

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1 hour ago, Lee Coll said:

This is the first issue I've had using Loft Surface and considering the two NURBS shapes I'm trying to use to transform into a varying-section "elbow", I just can't figure out how to allow VW to accept the command, without de-selecting both items with nothing happening.

 

Try selecting one of your shapes and reversing its direction by clicking the "reverse direction" button in the OIP. Often this will solve the problem.

 

Kevin

 

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I tried that Kevin and a simple loft does work.  That doesn't gve the swept result that Lee is after though.  To do that you need a rail and I can't get the loft to work with a rail curve.

 

768774689_Loftresult.thumb.png.7d48251020fe59ca976d618c83ebd03f.png

 

I suspect the problem is because of the two extra segments in the second curve.  In my experience lofts are problematic when you have curves with different numbers of segments.

 

Lee may have to look at doing this with a Subdivision object.

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I may go the Subdivision route starting with a torus, then taking a quarter of that tweak the end that is the larger of the two sections.

 

Thanks!

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I tried a quarter sweep but the bend wouldn't convert to a subdivision object.

 

I also tried lofting with a rail from two objects that had the same shape and it also wouldn't work.  ie. from one with two very short vertical straight line segments (1 mm) to one with longer vertical straight line segments (100 mm).

 

There must be a way to do it.  Hopefully the Vw Inc. experts can explain how to do that.  Also from a rectangle to a duct shape of that type.

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Here's how I would do it -

  1. draw the two profile shapes to create a straight segment.
  2. loft using Loft tool in "no rail mode" and with the "Create Solid" checkbox selected.
  3. switch to front view and use the Deform tool to create the 90 degree bend. Use the "bend solid mode" and have "finite length mode" active.

File attached with all the different stages.

 

Lofting the curved object is probably possible. I think using three profiles with the same number of points would be the way to do it (0, 45. 90), profiles only no rail. The bend method is far more predictable and reliable though as the Deform tool is more recent coding.

 

Kevin

 

388361227_ScreenShot2018-11-05at7_32_35AM.thumb.png.ceb11b6db09f66d9035f416451691b84.png

Bend Elbow.vwx

Edited by Kevin McAllister
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Many thanks - I have to create an arc path and note the length of that arc to provide the extrude value to give me the appropriate major and minor radii.

 

Regards - Lee

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