T-Spline Tip: Defining Regions For Conversion

While Skype-ing with Matt Sederberg at T-Splines today, he turned me on to a feature of T-Splines that I’d never even knew existed, one that I think is very useful to what I do.  We were chatting about some bugs I’d encountered on the cowling file for the Giles G-200, which they are addressing.  I had found what I thought was a T-Spline bug when I converted the surface to NURBS, but it turned out to simply be the Rhino display mesh settings.  This lead us into a discussion about conversion of T-Splines surfaces to NURBS, and what to look for.  He said “well have you played with the Define Regions for Conversion tool?”  The what?  Nope, never even knew it existed.  So here’s how the cowling looks right now as as T-Spline surface:

Let’s convert that to NURBS and see what we get, just using the default options:

Notice how the isocurves in the areas around the star points are more dense, and how that density gets sent back to the rear edge of the cowl?  There’s no real need for that additional density back there, and it makes life more difficult down the road when you’re doing your mold layout and creating joggles or offset surfaces from this surface.  Until today, I just thought that was the way it was, and there was nothing to do about it.  However, using the Define regions for conversion command under T-Splines->Utilities you can actually isolate that increased isocurve density to only the front portion of the cowl, where it is indeed needed.  Start the command, and then click on your surface.  It’s a little hard to see, but when you mouse over the surface you see the NURBS region edges highlighted in green:

What we’d like to do is contain that increased isocurve density to only the front portion of the cowl, so double click on one of the edges that form the first edge loop that goes around the cowling:

Now it knows to make the front portion one region, and the back portion another.  So let’s convert to NURBS now and see what we get:

Lo and behold, the increased isocurve density is now isolated to only the front portion of the model.  Nice!  I know that for myself, this will make things much easier when I go to design joggles and such for molding and tooling.

One Response to “T-Spline Tip: Defining Regions For Conversion”
  1. diego says:

    it’s very usefull
    thanks for share it!

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