Wednesday, November 4, 2015

5-sided Surface challenge in Rhino 3D

Rhino is a NURBS modeling program, so ideally every surface created in Rhino should has 4 sides with isocurves running on it. However while making 3D models in Rhino, sometimes I came across with some details that require 5-sided surfaces. Then the question becomes how do you create a 5-sided surface?

I googled a bit by key words "5 sided surface rhino" and here is one comes out on top of search result: http://v5.rhino3d.com/forum/topics/surface-challenge. It is a Q & A thread started by Justin from Australia in Rhino 5 forum.

I share the same reaction with Justin about the quality of patched surface if I use Patch command to create a 5-sided surface. I resonate with his thoughts such as "Network curves doesn't work as there is 5 sides", "Patch doesn't make the edges tangent .. and when you zoom in they are not connecting"

John brock from Robert McNeel & Associates offered his 2 solutions, which I think make sense:

"The first is to extend curves so you can make a 4-sided surface, then Trim away one corner to make the 5th edge. Your model suggests the boundary curve could be the Trimmed edge, suggesting the two surface edges be the edges to extend."

"The second is to create an interior curve that goes from one corner across to another edge. Then you would be modeling two surfaces instead of one to fill the 5-sided hole."

Another method is to buy Autodesk Shape Modeling Plug-In for Rhino. This is a program that allows real-time creating and modifying Class A surfaces. Class-A surfaces are used extensively in exterior design of a car.

And Michael G. provided a file with surfaces modeled in Autodesk Shape Modeling, and I opened it to review. As you can see the image below I cropped from the file, the yellow surfaces in the foreground were created in ASM versus red one created in Solidworks.

I added zebra strips to the 2 group of surfaces and found that the surfaces qualities are very close. I am just wondering if all I need to model in Rhino are generally for products apart from automobiles. Do I need to spend $1,325 to buy the plug-in?

 
 


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