Change surface without moving contour [solved]


I need help to modify a surface using control point, but without modifying position of contour.
Basically, I would like to modify the shape of a boat’s roof but without the edge of my roof separate the sheer line.

Is there a command or trick able to solve my problem ?

Thanks for your help

Well, if I get you, you need to have enough knots between what you’re trying to edit and what you want to leave alone that it won’t be effected. The number depends on the degree of the surface, for a degree 3 surface it’s 3.

Hi Ogrim - try this:

  • Place some points or curves that you would like the surface to pass through.
  • Start Patch and in the dialog, click on Starting Surface.
  • Select the original surface as the starting surface, I’d say Delete Input unchecked, or keep a copy, just in case.
  • Set Pull to 1 and Preserve Edges. I’d start with Stiffness at 1. OK.

Any good?


not really =S
I dont know why, but my original surface is convexe, the result of the patch function give a concave shape Oo. However, it fit my sheer line ^^

Can you post a file containing the surface and the desired new inputs?


On this file, you can see my hull, my roof that doesnt fit the sheer line and the result of the “patch” command.

Hi. Gave this a quick bash and using Some edge curves and a Loft I made the attached surface.
It is however not s single surface but it is editable without losing contact with the edges. - Michael VSCoque OYA 001.3dm (271.3 KB)

I cant open your file with my Rhino 4 version =S
can you convert into a Rhino 4 file ?

Here is file as v4 file:
Coque OYA 001-v4.3dm (270.7 KB)

Thank you very much,

Your method seems to work, even if I though there was a simpler solution, it will be great for my needs. Thanks all :wink:

Here is my try using the technique I described- two things to add:

  1. The orignal surface was pretty sparse in control points so modifying it using Patch does not hold the edges very well. I used InsertKnot Automatic a few times to give the original surface more points.

  2. The new surface needed to be retrimmed.

The red curves are the inputs for Patch.

Coque OYA_PG_V4.3dm (163.7 KB)