Strategy for modelling a complex helmet of non-uniform thickness


I’ve been struggling to find an efficient way to get the attached model of a helmet into a clean set of surfaces. My general plan was to separately model the upper, lower, and connective “shelf” layer as three surfaces, which I could then tweak, join, mirror, and solidify into a finished helmet. I’ve extracted a few cross sections from the STL file it’s sourced from, but the joining of the resulting curves seems daunting. The current stage of closing off the top portion of the upper shell has me stuck (doesn’t seem conducive to UV geometry), and is making me question my entire approach to this.

Any general advice, tips, or references to help with modeling this helmet are greatly appreciated.

Foam_Remodel 005.3dm (6.7 MB)

Surely I’m not the only one still using Rh5. Your file is unintelligible.

My apologies. Here’s a version saved as Rhino 5.

Foam_Remodel 005.3dm (7.9 MB)

Attached is not following your model 100% accurately, but this is the structure I would suggest for the outer surfaces. Basically think in easy to manipulate surfaces rather than trying to do everything in one go…

Foam_Remodel_sg.3dm (389.5 KB)

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This is very helpful, and looks fantastic – thank you. Can I inquire about your strategy in creating this? From what I can tell, it seems like you may have started by fitting a plane on the back and the side, and then trimmed each of them? It looks like the ridge on the back side was projected on, and maybe a blend surface was used. I’m guessing that the top panel and bottom perimeter panels were made with 2-rail sweeps. Many thanks.

There are multiple surface techniques you can use, but in this case I started with some degree 5 curves for the top, then used EdgeSrf and manipulated the controlpoints. Did the same for the back (reused 1 curve from top) and for the small surface on the front a 1-rail sweep (reusing again the curve from top) -->simple option to get a simple clean surface. The smaller side surface was built as a 1 rail sweep as well and manipulated. Then the larger side surface is based on the existing curves of the top and back surface, then manipulated until it matches the trimming line as closely as possible. Then trim it, and match the smaller side surface to that surface.
You can use the Symmetry command (history enabled) to keep the top back, smaller back and smaller front surface perpendicular to the mirror plane.
Finally the two surfaces on the back are based on the same surface, one has some control points pulled back a bit them trimmed with the curves in the file. Then connected with a blend surface.