Isocurve problem

Hi dears :smile:
I create surface 2 by EdgeSrf and mirror it to create surface 1 then i match surface 2&1 (curvature continuity-average surface) ,after that i want my isocurve of surface 1&2 have a shape like picture.1 but they have isocurve like picture 2



Below i upload Rhino(.3dm) file
audi R8.3dm (268.4 KB)

Hi Shayan- turn on points for the surfaces - you’ll see what is going on- this is a case where it would be better, probably, to have a degree 3 surface, 4 points, in the short direction. (Do your MatchSrf with ‘Preserve other end’ set to Position)
Or just manipulate the points on the degree 5 surface so that there is no reversal in the shape they make.

One thing I noticed is that your surface points and the points on the input curves are sort of 'all over the place" in Z. I would try to arrange points so that they are not ‘fighting’ the shape so much-

Red is my edit of your blue curve.
The curves have the same shape.

pgAudiSrfs.3dm (129.8 KB)



Thanks a lot dear Pascal for your very useful answer :smile:

Hi dear Pascal :smile:
In this topic i sent a picture of the 3D Car Modeling With Rhinoceros (Book) with my audiR8.3dm file that i had a problem with isocurves of surfaces. You answered me and sent pgAudiSrfs.3d file. I read your answer very carefully and did all of you said .I edited my audiR8.3dm file and got a result as same as your pgAudi.3dm file. Thanks very lot . But i have two questions :

As you see in the below picture the author for make curve"1" use InterpCrv (Degree=5 Knots=Chord) after that make surface “1” with EdgeSrf

Then he said :

“Surfaces are not optimal because of curve"1” (make with InterpCrv) . Due to uneven distribution of isocurve we can see that surfaces has multiple nodes. To correct this we need to use Rebuilt Surface Tool. As degree 5 and for point count choose 6. The division is ideal.’’

And you said:

Now my questions are :

  1. If i rebuilt the surface ‘‘1’’ (pgAudi.3dm file or my file that i edited )isocurves division are ideal but control point of surface are sort of ‘all over the place" in Z as you mentioned above,If i don’t rebuilt surface’‘1’’ the control point are ideal but isocurves division aren’t ideal as author mentioned it, what should i do now?

  2. Author used curve ‘‘1’’(create from InterpCrv with:Degree=5 Knots=Chord),2,3,4 and surface’s edge to make surfaces 1,2,3,4,Then rebuilt surfaces. And you (dear Pascal) if i well understand (from your pgAudi.3dm file) splited these curves(’‘1,2,3,4’’) then created surfaces without rebuilt them, which procedure is better to follow?


Hi Shayan - I personally prefer to get the curves right and have minimal work to do on the surfaces. Using interpCrv, it might be better to use the Uniform option, but in the end I’d prefer to have, where possible, the curves clean and nicely arranged (points) before making a surface from them.


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Appreciate dear Pascal as let me know to use your best experience