How to extrude a projected curve?

Hi guys,
I want to make a tire model. First, I made the overall shape then I went on to make the tread. For the tread pattern, I used an image so as to boarder the pattern using curves. I made a close curve as you see in the image. Then I used projection tool to project the curve shape over the tire. When I extruded the projected curve, it failed to make it solid means it didn’t cap the border. What is the problem?
2- Is there any practical method to model a high quality and detailed tire tread?
Please guide me.

01.3dm (1.6 MB)

Hi Alex, when posting cases like this one, it probably will be easier for other users to help you if you post the 3DM file along. that way, other people could check if there are any gaps, overlapping curves or anything that could prevent you from getting a solid.

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Hi, Rodri
I provided the file.

To create a solid from a curve the curve must be closed and planar. From Rhino Help for the ExtrudeCrv command::


If the profile curve is closed and planar, both ends of the extruded object are filled with planar surfaces and joined to make a closed polysurface.

The projected curve is not planar. You need to either create a surface inside the projected curve, and extrude the surface, - or - extrude the curve and then create surfaces to close the extrusion.

One way to create a surface from the projected curve is to copy the tire surface, trim it with the projected curve, and then ShrinkTrimmedSurface the trimmed surface. However since the curve currently projects onto a seam in the tire surface the result of the trim and shrinking is several surfaces, and for ExtrudeSrf you need a single surface. To avoid the same rotate the tire surface so that the projected curve is no longer on the seam.

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Hi Alex - see the attached file - does that help?
01_PG.3dm (668.6 KB)

@Alex_Wright - one advantage of doing things this way is that you get to make the extrusion from the original, clean, simple shape curves of the tread and not from relatively messy and inexact projected curves. However, in this context what you really may want to do it make the treads flat and FlowAlongSrf from a plane to the tire surface.


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Thank you very much. It was helpful.