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Tracing 3D shapes using a nurbs curve


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Hi, 

I'm trying to model a fairly complex spiral shape and was planing to do this by using a series of helix spirals as a template and then tracing over with a nurbs curves to give me a continuous shape which I can then use as a path to create a loft shape.

 

I started the process using VW 2016 and used the nurbs curve to create my first path. I have now had to shift to a different machine operating VW2011. When trying to create the next 3 paths, the nurbs curve doesn't seem to be drawing in 3D / tracing the shape accurately. Any ideas as to why this might be? Is it to do with the downgrade in software?

 

I'm up against the clock on this one, so would appreciate any suggestions.

 

I have attached a couple of screen shots to give you an idea of what I'm doing, if that helps. The spiral on the right is the nurbs curve that I was able to create in VW2016 and on the left is my template.

The second image is a sketch of what I am trying to model.

 

Any other suggestions for how it could be better modeled?

 

Update - 

It seems as though my nurbs curve just isn't snapping to the 3d template that I have made.  is there a way to get it to snap to the nurbs curves in my template?

Screen shot 2017-03-04 at 12.19.48.png

IMG_2189.JPG

Edited by Moore Martin
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5 hours ago, Moore Martin said:

Hi, 

I'm trying to model a fairly complex spiral shape and was planing to do this by using a series of helix spirals as a template and then tracing over with a nurbs curves to give me a continuous shape which I can then use as a path to create a loft shape.

 

I started the process using VW 2016 and used the nurbs curve to create my first path. I have now had to shift to a different machine operating VW2011. When trying to create the next 3 paths, the nurbs curve doesn't seem to be drawing in 3D / tracing the shape accurately. Any ideas as to why this might be? Is it to do with the downgrade in software?

 

I'm up against the clock on this one, so would appreciate any suggestions.

 

I have attached a couple of screen shots to give you an idea of what I'm doing, if that helps. The spiral on the right is the nurbs curve that I was able to create in VW2016 and on the left is my template.

The second image is a sketch of what I am trying to model.

 

Any other suggestions for how it could be better modeled?

 

Update - 

It seems as though my nurbs curve just isn't snapping to the 3d template that I have made.  is there a way to get it to snap to the nurbs curves in my template?

 

 

If the screen shot is of VW2011 you'll need to switch the plane dropdown (top of the drawing window) from Screen Plane to Layer Plane (sometimes Automatic) to snap properly in 3d.

 

If you duplicate your Helix Spiral curves, you can Ungroup them to convert them directly to NURBS curves (for whatever reason, convert to NURBS doesn't work and generates an error message). Also, if you have multiple NURBS curves you'd like to be a continuous path, use Modify>Compose.

 

To make a solid object you'll likely have to use Extrude Along Path / Loft or create some NURBS surfaces and Shell them. From the look of it your shapes would need to be created in at least three pieces.

 

Kevin

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Hi Kevin, 

Thanks for your response and comments. I have tried tracing the curve in both screen and layer planes and neither seem to work. I am attaching a couple of screen shots so that you can see whats happening.

In the first image, the pink line is the nurbs curve that I am using to trace the shape in Right Isometric view. The second image shows what happens to my curve when I switch views to Left Iso view.

I'm doing it in the very same way that I created the green spiral in the earlier image, which is accurate in all views. I feel that I must be missing something quite simple, but can't figure out what.

 

The helix spirals have already been broken down into nurbs curves, but only one segment of the overall shape is a true helix. Therefore, I am using the two other helix spirals as a guide to create the shape I want.

The plan, when I manage to trace the three additional curves I need, is to use the loft tool to create the solid shape.

 

58bb2f19f18b3_Screenshot2017-03-04at21_06_52.png.0e7a6479d623a23484f9ddcbef88df41.png58bb2f30c2d52_Screenshot2017-03-04at21_20_47.png.a1c27b4f54cd61bd6a2d7db92b52d463.png

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Hmmm I see. Can you extract the edge of the NURBS surface and trim the resulting curve to what you need?

 

As an aside, part of your issue may be related to the degree setting of your NURBS curves. Your screen shot shows a degree of 20! Normally you would only need them to be degree 1 (straight), 2 (curved in a 2d direction) or 3 (curved in a 3d direction). Double click on the NURBS curve tool to set the initial degree.

 

Kevin

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Here I created 2 helices and one connecting curve, placed  3d loci on the helices at the 90º axes (although you could pick the 45º for more accuracy) and traced a 3-degree nurbs from locus - locus.

More consideration of the correct tangents for the connecting curve will produce a more accurate result.

 

 

 

Screen Shot 2017-03-05 at 5.13.22 AM.png

Helix_ribbons.vwx

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