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Anomaly in Wedding Ring Design. Help!
Hey everyone,
I’m using Cinema 4D to design my fiance a custom wedding band, however I am running into a strange anomaly that I am not sure how to fix. It’s driving me mad.
Basically, I am using a square spline (with rounding) as the contour of a circle-spine based sweepnurbs object to create a wedding ring shape. I wanted the ring to taper inward toward the bottom of the ring to make it feel more feminine. When I adjust the sweepnurb’s scaling curve in the “Details” panel, I get the effect I want, however, there is a strange “kink” in the circle where the spline starts and ends. You can see it in the following screenshot:
https://www.salttank.net/images/RingTaperAnomaly.jpg
I’ve also uploaded the source file here:
https://www.salttank.net/images/RingDesign.zip
Thanks to anyone who can help me fix whatever is causing this.
-Eric
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4 Replies
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it’s harder to see what’s going on (not that it should happen but rotation and keeping ‘up’ straight is tough in any program) if you construct it as you did – putting the rectangle in the orientation it ‘should be’ in before sweeping.
This has two rings – one built like yours but with the rectangle in the ‘normal orientation. Toggle banking on and off in that one and you will see what’s going on. I don’t know how to stop that but the other one is another way to do it – with Rail Scale.
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Why wouldn’t you use a tube object and hypernurbs. Just make a tube with fillet on, lower the segments, drop it under hypernurbs, make some looping knife cuts if you need it more squared. and as for the tapering. just select the bottom half and modify the scale. This way, you can also model the part where the diamond is held within the same object.
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You’re having a banking problem here, which you can see if you uncheck the “Banking” box in the SweepNURBS. Cinema thinks the profile curve is flipping as it goes around the circle. The banking parameter tries to correct for that, but in this case it isn’t doing the job perfectly.
You can fix it by using a rail spline and the “use rail direction” option. In this case you would just copy the circle spline and drag it just below the existing circle spline inside the sweepNURBS (same heirarchy level — not as a child). Then move that new circle spline a little bit in the Z direction (doesn’t matter which way).
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Use a basic box and hypernurbs and you can create that thing in 10 seconds. No weird anomalies and glass smooth. I can whip one up for you if you are interested.
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