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shell tool fails on nurbs surface


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I made it work with a different approach:

?Put the drawing in Top/Plan

?Extract the edges - I found 4 of them.

?Group the edges and enter the group to work in isolation (or put them on another layer.

?The edges surround a longish leaf shape, pointed at both ends.

?Compose the edge segments in pairs to create two long NURBS curves, coincident at the leaf points.

?Make both NURBS same direction, eg arrows point from bottom to top of view.

?Loft Surface between the two curves.

?Result is a single NURBS surface with a few divider lines in it.

?Engage the Shell tool and click the surface.

?Shift click to highlight the other sections until all are selected.

?Press Return or click the green checkmark to create the shell.

Don't know why your surface from curves does not shell. Maybe the orig curves were mixed directions, or needed to be mixed directions.

-B

ubbthreads.php?ubb=download&Number=10349&filename=Loft&Shell.png

Edited by Benson Shaw
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Tryed it like Benson.

That works fine, but it`s strange that the other way doesnt work?

Maybe has Jim an answer on why this doenst works?

Included the file with the curves. Changing the direction of the curves doesnt work as wel if you want to shell a nurbs surface that is created by 'create surface from curves'

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Buzz - My theory for shell failure:

Shell 3.vwx won't go because Shell tool cannot create intersecting geometry required at the pointy ends. The Shell tool creates an offset along the normal to the surface at every point. The end points are undefined. IE they have normals in several directions. Think about what the shell would look like at the end points - which direction would it have thickness?

If the surface to be shelled is trimmed a bit at both ends, the Shell will work at 127 thickness.

The original NURBS Curves and resulting Loft Surface measure 1000 (plan projection). I tried several trim lengths to minimize the modification. 9950 was still too pointy. 9925 worked.

I trimmed in the plan view x direction. Changing the trim direction at each end, so it's more perpendicular to the curve "aggregate" might allow closer trim and longer shell.

I also tried nudging the curves apart (instead of trimming) so they don't actually touch at the end points. No joy there, but greater separation and/or changing the 3d nudge direction might do the trick.

-B

ubbthreads.php?ubb=download&Number=10355&filename=Trim&Shell.png

Edited by Benson Shaw
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Here is a cheater approach: Offset a duplicate of the surface.

Thickness is not constant on surface normals, but rather on z axis (or other axis depending on rotation at time of offset).

ubbthreads.php?ubb=download&Number=10356&filename=Offset%20Lofts.png

Result is 4 surfaces surrounding a volume. Not a real solid.

To make a solid with actual volumetric properties, select the 4 surfaces>Model>Add Solids, then Modify>Convert>Convert to Generic Solid

Rotate the solid into position if needed.

-B

Edited by Benson Shaw
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Thanks for the help Benson and the clear explination!

I tried the cheater approach, but somenthing went wrong. I only saw in wireframe the nurbscurves, in open gl there was nothing. I will give it another try.

I dicovered the combine tool. Its great that it makes fluid transitions between two different nurbssurfaces. Really nice and easy.

Its a pitty that the push/pull tool and the normale extrude doesnt Worms on nurbes, do hou know why that is?

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I only saw in wireframe the nurbscurves

In the "cheater" approach, create a Loft Surface from your 3 curves. Then rotate and duplicate the surface according to the steps shown.

I dicovered the combine tool. Its great that it makes fluid transitions between two different nurbssurfaces. Really nice and easy.

I like your discovery for joining the two surfaces:

Connect/Combine Tool in Basic Toolset

>Dual Object Connect Mode (2nd mode)

>>Blend option

Click to highlight each surface. Click OK to accept.

Creates a new NURBS surface between the surfaces.

I had not used Connect/Combine for this before (or forgot). Thanks for pointing it out!

Its a pitty that the push/pull tool and the normale extrude doesnt Worms on nurbes, do hou know why that is?

Extrude only works for 2d planar shapes. Push pull seems limited to planar surfaces, but I don't know why.

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