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Summary

Some tips from Rhino user Steve Howden for flattening surfaces to 2d patterns. The specific context of this post to the Rhino news group was flattening for fabric but most of this should apply to compund curve surface development from Rhino.

There are a variety of ways of doing this, but first (to make sure we are

speaking the same language) let me point out that there are two types of

surfaces;

a/. developable, ie. no curvature in one dimension, eg cylinders. cones

b/ double curvature eg spheres

So you have two options.

• You could design your bags by creating the seam lines and lofting

(developable) between them and then using _Unrollsrf to get your patterns

• Or (and this will give you more flexibilty in designing) model up your

shapes useing whatever method you like and then projecting or pulling seam

lines to the surface and splitting that surface up. Note, in V4 there is a

very handy tool called _Shortpath that gives a "geodesic" curves on the

surface which can be good for this.

Once you have these split surfaces you can flatten them useing one of the

available methods for dealing with double curvature (ie non developable)

surfaces. Note that any surface flattened in this way WILL be an

approximation, but sensible seaming will minimize this.

-

The tools currently available are:

Smash.

This is free (part of V4). Be careful to try both of the unrolling

directions along U and V to see which gives best result. Also watch the

dialogue which will tell you what % change in surface area the unrolling

caused. If it tells you the resulting surface is 65% smaller afetr unrolling

then you know it has all gone horribly wrong.

Expander

*Discontinued as of Jan 31'st 2007

Not free plugin for V3. This is my current favourite. It gives extremely

good results and has the major advantage of giving you a colour gradient map

showing clearly how much stretch and compression was needed to create the

flattened surface. Available from:

http://www.shipconstructor.com/productsandsolutions/companionproducts/expander.html

For an alternative to expander in V4, see:

http://en.wiki.mcneel.com/default.aspx/McNeel/AdvancedFlattening.html

Laminadesign

Rather nice stand alone program that can read .obj files from Rhino. Suffers

from not having a good way to split up surfaces, so you have to do it all

first in Rhino, then export and expand. If you don't like the results you

have to go back to rhino, resplit, export again and re-expand.

Available from: http://laminadesign.com/

TouchCAD

Stand alone program with a modelling methodolgy that does my head in. It

does have the MAJOR advantage of real time flattening, ie. change a model in

3D and it istantly updates the 2D patterns. This brilliant for getting

optimum fabric useage.

Available from: http://www.touchcad.com/

Note you cannot get rhino surfaces into TouchCAD. You have to model in TC.

Optitex

Not a flattening program per se but it has some very nice 3d features which

allow you to take your flat patterns and stitch them together, then simulate

how the final product will pull together. You can define the fabric

characteristics, seam tension and it gives a VERY accurate model of the

final product right down to seam wrinkles and folds. It is also a complete

pattern design, nesting, grading and CNC cutting controller. We've been

using it for ages and love it. Expensive as hell but worth every cent.

I was told yesterday by the CEO that flattening is in Alpha and will be

available in the next version. Fingers crossed.

Available from: http://www.optitex.com