This is a part from following forum posting. I wish to know why Ruled Surface works whereas Extended Surface does not work.
The simplest answer is that the rule surface does not care how the original surface was created. It simply creates new faces that (with the settings you selected) are tangent to the existing surface at the existing edges.
The Extend Surface cares deeply about the existing surface. It want to know its mother and father and, if possible its grandparents. It wants to know its DNA. Why? Because the Extend Surface thinks very highly of itself. It thinks it can travel back in time and reverse engineer the existing surface to re-create its grandparent.
What is really funny, is that sometimes the existing surface has no idea who the parents are. In that case, the Extended Surface is trying to concoct an alternative history by extrapolating what it knows about the existing surface. The results, in such cases can be strange or fail entirely. That is usually true for non-analytic surfaces.
Maha Nadarasa wrote: Thanks for your valuable contribution it is informative, this method can reduce my tree length in making a model. Sometimes in this situation I see both the Tangent Relation and the Equal Curvature relation in this circumstance which one to select.
Maha Nadarasa wrote:
Thanks for your valuable contribution it is informative, this method can reduce my tree length in making a model.
Sometimes in this situation I see both the Tangent Relation and the Equal Curvature relation in this circumstance which one to select.
Depends of which one you need in order to control the curvature transition in the neighbourhood of the edge: C1 or C2.
I tried Equal Curvature method. But it gave incorrect result.
Maha Nadarasa wrote: I tried Equal Curvature method. But it gave incorrect result.
Please upload the file. That is strange, unless there is a small face there.
File has bee already attached.
Watch the attached video. File is also attached.
I can understand that if not appropriate angle is selected spline either can go up or down. It does not come for me. In this situation I usually use either Face Curve or Intersection Curve because spline can be sketched at any angle and finally Add Relation can establish tangent relation.
I will expand on this topic once I get home.
Thanks for the reply.
In SW extend surface sometimes does not extend the underlying surface topology and makes it up; sudden wrinkles in extensions. This often happens when you try extending edges from multiple surfaces that are knitted together, like in the images below. Normally you can get an extension of the underlying surface topology by extending surface edges individually and/or a mix of extend and untrim.
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