# Combining Nurbs Surfaces

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Ok, Created a rectangle and then used the Create Surface From Curves command to make it a nurbs surface. Then I set the U and the V Degrees to 3. I then moved the handles inside the surface using the 3-D Reshape tool to create an undulating plane. The 4 sides of the rectangle are still in the same z coordinate (0), and all of the handles I moved were in the positive z direction.

Now I created another rectangle and again used the Create Curface From Curves command. It is bigger than the first surface, and the first surface is centered in the second. I then traced the first surface with a rectangle and used the Project and trim to to clip the second surface.

Now what I'd like to do is combine the first and second surfaces into a single nurbs surface that can be further modified with the 3-d reshape tool.Is this possible?

Thanks

• Vectorworks, Inc Employee

You can add the surfaces to create a solid using Add Solids command. But you cannot create a single surface out of the two surfaces as they do not have geometric continuity at the boundary of the first surface where they join. Incidentally, to be more precise you could extract the curves out of the boundaries of the first surface and compose them into a single NURBS curve and use that for trimming.

Yeah, I tried the Add Solids, but you don't get the same ability to edit the geometry as the Nurbs surfaces have. As far as extracting the curves and using them to trim, I'm going to have to think about that one, I'm not sure I understand what your saying.

But I figure I'm going to have to start thinking backwards sometimes to end up where I want to be.

Thanks

• Vectorworks, Inc Employee

Yes, when you add solids, you don't have the same flexibility. But the 3D Power Pack design is done with this in mind. Wht ayou do in such situations is - convert the Add Solid to NURBS surfaces using Convert To NURBS command and then manipulate these NURBS surfaces and then add them back together if necessary.

• 12 years later...
... cannot create a single surface out of the two surfaces as they do not have geometric continuity at the boundary of the first surface where they join.

It seems so basic for 3d modeling: why can't a simple command be developed to join 2 NURBs curves into one curve, as can be done with polygons?

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