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Tobias Kern

wish: multiple conversions of 2d objekts to nurbs-surfaces

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hi,

you only can convert one 2d object (rectangle, polygon, ...)

at once to a nurbs surface, if you select more than one,

vw 20150 shows an error hint.

so my wish:

multiple conversions to nurbs-surfaces of non-connected 2d-objects!

cheers

johnny

Edited by johnnygitarr

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hi,

you only can convert one 2d object (rectangle, polygon, ...)

at once to a nurbs surface, if you select more than one,

vw 20150 shows an error hint.

To clarify, you are referencing the "Model > 3D Power Pack > Create Surface from Curves" command when used on multiple planar objects?

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I'm a bit confused by this wish, I guess because I've never used "Model > 3D Power Pack > Create Surface from Curves" to convert 2D objects to NURBS. Its not really designed for that because its trying to create one surface from a network of curves. I could see how it could work for closed curves like rectangles and circles because they technically are a network of curves.

I actually wish Modify>Convert>Convert to NURBS, which is really designed for the conversion you're trying to do, was a little smarter. It should convert closed, filled shapes (i.e.. solid circles, rectangles and polygons) to NURBS surfaces. It should convert open shapes (i.e.. unclosed polygons or polylines, lines) or unfilled shapes (ie. fill set to none) to NURBS curves.

In the long terms, all 2d shapes should ultimately be seen as NURBS curves or surfaces like other programs.

Kevin

Edited by Kevin McAllister

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+1 to the wish

+1 to Kevin's points

Except I do want to preserve the legacy 2d objects. I want access to objects that can be guaranteed to create planar, remain planar throughout edit, and exist on a known plane (esp the layer plane).

I'm OK with some system where default NURBS or 3d poly planar objects can be converted to legacy 2d, or a 2d legacy object can be derived from the NURBS curves and surfaces in Kevin's discussion.

-B

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Objects like Rectangles and other "Planar" objects will likely never ever truly go away, but be handled in the background more like Kevin describes. Preferably removing the need for the user to understand the difference or act in any way differently because of what objects they are working with.

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"It should convert closed, filled shapes (i.e.. solid circles, rectangles and polygons) to NURBS surfaces."

Please, no!

This is not good. when you convert to nurbs surfaces, you get trimmed objects, which is a degeneration, because vital information is lost. So please do not use Kevins wish as it stands, Jim.

There has to be two separate commands for converting to curves or surfaces – or all 2D objects – open or closed – should be converted to curves first.

I do not like those trimmed surfaces, because they are a dead end, that cannot be used for a number of further commands.

Edited by Kaare Baekgaard

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I'm happy to backtrack.

But I am looking to improve upon the two step process which can get very involved when you're translating a lot of shapes. Surfaces are needed for commands like "Stitch and Trim". And you can easily get the curve if needed by using the Extract tool.

I still feel "Model > 3D Power Pack > Create Surface from Curves" is not intended for conversions.

Is it possible for a circular shaped NURBS surface to not be a trimmed surface? (I have no idea myself.)

KM

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Kevin, the problem with extracted curves is, that they tend to pick up extra vertices which makes them less clean to work with. For most purposes that may not matter, but if you are creating double-curving objects like the dinghy below, you need to keep it clean.

Yes you can create circular shaped surfaces, that are not trimmed surfaces:

Start by making a 3-line C-shaped polygon where the open side is twice as wide as it is tall.

Convert it to a nurbs curve object.

Use the 3D reshape tool to change the vertex mode of the two corners.

Use the OIP to change the weight of the two corner vertices to 0.5. The curve has now become a half-circle.

Reflect & duplicate the half circle curve, so it becomes two halves of a full circle.

Loft the two curves.

The resulting object is an 8-vertice circular surface, that can be reshaped into any oval.

I really wish, there was an easier way to do this, but most other methods only give me trimmed objects.

https://drive.google.com/file/d/0BxL3Oyph55RRaEhFWlllYnNpanc/view?usp=sharing

Edited by Kaare Baekgaard

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Kaare,

Thanks for the detailed explanation. It was quite helpful.

Kevin, the problem with extracted curves is, that they tend to pick up extra vertices which makes them less clean to work with.

Is this true for all programs (ie. Rhino) or just VW? Do we need to wish for better curve extraction?

Loft the two curves.

The resulting object is an 8-vertice circular surface, that can be reshaped into any oval.

Interestingly you can use "Model > 3D Power Pack > Create Surface from Curves" instead and get the same result here. It seems like we should be wishing for non-degenerative conversion to NURBS surfaces (ie. VW should try to convert to a clean, untrimmed surface first before falling back on an untrimmed surface as a result.)

I tried the same process for creating a surface in Rhino and then imported it into VW. Clearly the import/conversion engine defaults to trimmed surfaces. Even weirder when you "untrim" the Rhino created circle it stays a circle. It seems VW needs some tweaking under the hood when it comes to NURBS.

Kevin

Edited by Kevin McAllister

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It seems VW needs some tweaking under the hood when it comes to NURBS.

Yes! Please! Lots of tweaking. Enhance NURBS modeling along in parallel as Sectioning and other polygon model features are added and improved.

Drape Surface seems able to create complex, untrimmed NURBS surfaces. Why not similar capability in the Create Surface from Curves and other surface creation processes in vwx?

-B

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Objects like Rectangles and other "Planar" objects will likely never ever truly go away, but be handled in the background more like Kevin describes. Preferably removing the need for the user to understand the difference or act in any way differently because of what objects they are working with.

++++++ 1

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