I think I am getting a pretty good grasp of nurbs modeling. One question I have though is on the proper technique for creating panel lines. Say the spaces between the hull plates on an aircraft wing.

With subpatch modeling I would bevel in the edges of the shape, add a controlling edge to tighten up the edge and then subpatch it, this gives me nice lines between the different plates when it is subpatched.

I have taken the same approach with nurbs. Start with the basic shape, trim the cuts, and then I used shell to add thickness to them and fillet the connecting edges. This gives me the look that I am after but I am not sure if it is the proper, or best way of approaching this problem. The only other solution that I could think of was to sweep a circle along the panel lines and boolean them out. That seemed like it would create more problems to me, but that might be the anti-boolean mentality that comes from years of subpatch modeling.

Hi Andy, so if you want that particular kind of rounded edge shape on your panel then probably the technique you already used by doing Shell + edge fillets would be the best way to go.

Or possibly instead of using Shell you might want to just cut the solid into multiple solids by doing a Boolean with a curve as the cutting object, then fillet the edges of those individual solids.

So for example if you have a sphere, you can have a cutting 2D curve like this:



Then if you select the sphere and do a Boolean difference and use the curve as the cutting object, it will divide the solid into 2 solid pieces like this: (shown slightly separated for illustration):



Then you would be able to fillet those edges:





> The only other solution that I could think of was to sweep a
> circle along the panel lines and boolean them out.

Yup, that would also be a typical way to do it, and depending on what you want this way can give a slightly different more distinct groove shape.

See here for an example:
http://moi3d.com/forum/index.php?webtag=MOI&msg=817.8

One tip though - if you have tubes that are going to criss-cross over top of each other that can be more difficult for the surface/surface intersector to resolve, but if you make crossing ones slightly different diameters that can help to avoid intersection problems.

Sometimes things that just barely touch or barely graze each other can run into boolean problems.


> That seemed like it would create more problems to me, but
> that might be anti-boolean mentality that comes from years of
> subpatch modeling.

This is one of the big differences between sub-d and NURBS modeling - with NURBS modeling you normally want to incorporate booleans as a primary way of working rather than as something to avoid.


For some kind of similar things where you want to have recessed or protruding bits you might use a technique where you slice the surface up and then use Shell or Extrude to make the protrusion or indentation in a localized area, like this:
http://moi3d.com/forum/index.php?webtag=MOI&msg=3024.4


And also in other circumstances the Inset command can help:
http://moi3d.com/2.0/docs/moi_command_reference7.htm#inset
That's similar to shell in that it produces a new face that is created from an existing one by offsetting, but Inset also kind of shrinks the offset face inwards as well.


- Michael

Great info, thanks again.

Andy

Hi Andy,

> I have taken the same approach with nurbs. Start
> with the basic shape, trim the cuts, and then I used
> shell to add thickness to them and fillet the connecting
> edges. This gives me the look that I am after but I am
> not sure if it is the proper, or best way of approaching
> this problem.

So just to clarify - there is nothing wrong about that technique of using Trim + Shell + fillet.

But it can be somewhat more convenient in general to stay working with all solids when possible, it can end up saving some steps. Working with individual surfaces is a somewhat more "low level" kind of an approach.

So for example in your model there instead of doing Trim + Shell to generate the multiple pieces instead you could keep things in solids by using boolean difference on the solid to generate the multiple pieces.

- Michael

One more question along these same lines. Is there a way to inset a particular surface while not extruding it?

For example I have this surface.



I want to do an inset, similar to the image attached, but I don't want to extrude it inwards. Bascially I want an inset but with a 0 height. I tried the seperate height option, but entering 0 would cause the tool to not work.

Hi Andy,

> Is there a way to inset a particular surface while not extruding it?

Inset will always try to make a protrusion inwards or outwards, but if you enable the "Grooved" option and leave the groove width to be empty or set groove width to 0, you will get the "plug" as a separate object which will be flush to the original shape.

Or depending on what you want you may actually want to put in a small value for the groove width so that there is a little bit of separation between the outer and inner pieces, like this:

Original surface:



Inset with "Grooved" option enabled, with a small groove width:



- Michael