Adding a wrinkle, or kerb or cease to a surface

I want to add a line of control to a nurb surface to be able to pull a sort of
knuckle or cease, think about a BMW 7, see attached file.

The surface itself is a trimmed NUBS with loads of control points! I have upoloaded the file with a projected
line where the knuckle should be situated.
The Knuckle should not extend over the whole lengthe of the surface!
Your valuable helpü is very much appreciated.

ID: d2e15032-6b6c-41ba-8591-64a16a652e30 (6380)
Layer name: Flossenstab
Render Material:
source = from layer
index = -1
Attribute UserData:
UserData ID: CE28DE29-F4C5-4faa-A50A-C3A6849B6329
Plug-in: 17b3ecda-17ba-4e45-9e67-a2b8d9be520d
description: User text (1 entries)
saved in file: yes
copy count: 25
Valid surface.
Trimmed surface with 1 hole(s)
NURBS Surface
“U”: degree =3 CV count = 73 (0 <= U <= 7057.53)
“V”: degree =3 CV count = 17 (0 <= V <= 944.923)
Edge Tally:
14 boundary edges
Edge Tolerances: 0.000107224 to 0.00442802
median = 0.000813015 average = 0.000945563
Vertex Tolerances: 0.000107224 to 0.00442802
median = 0.000813015 average = 0.000945563
Render mesh: 1 fast mesh 473 vertices 509 polygons
Analysis mesh: none present
Cease or knuckle.3dm (2.3 MB)

Hi Klaus - using your curve on the surface as the location:

Cease or knuckle_PG.3dm (2.7 MB)

  1. OffsetNormal (red)
  2. Two BlendCrvs from the ends of the offset (Blue)
  3. Two OffsetCrvOnSrf, (green) These offsets will control how ‘sudden’ the crease is.
  4. Explode these and throw away the ends.
  5. Loft, ‘straight sections’, the offsets and the joined normal and blend curves (red curve) I used Rebuild to 32 points.
  6. Trim the base surface with the border (DupBorder) of the loft object.
  7. Explode the loft.
  8. MatchSrf the loft for curvature, Preserve other end set to Position.
  9. To kill the hard edge, you can build another transition surface, or MergeSrf with the ‘roundness’ set low, like .1.


1 Like

Thanks Pascal,
neat solution, have a good nights sleep now.