Rhino developable surface error-what's wrong

Discussion in 'Software' started by M.Ezell, Mar 13, 2011.

  1. DCockey
    Joined: Oct 2009
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    DCockey Senior Member

    Did you start with the file M. Ezell uploaded in the first post, or the file I uploaded after I reworked it?
     
  2. Dean Smith

    Dean Smith Previous Member

    the last in thread
     
  3. Dean Smith

    Dean Smith Previous Member

    cant open first did you create in r5 4 wont open it
     
  4. DCockey
    Joined: Oct 2009
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    DCockey Senior Member

    I'm DCockey, not M.Ezell the original poster. I didn't create the Rhino 5 file in message #1, Solway Dory.3dm. I downloaded it, opened it in Rhino 5, saved it as a Rhino 4 version. Then opened it in Rhino 4 and reworked the surfaces slightly, used UnRollSrf to unroll the revised surfaces, and saved it as Solway Dory DC 1.3dm. Then I uploaded it in Message #7.
     
  5. DCockey
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    DCockey Senior Member

    Opened the original file again in Rhino 5. Inconsistent results when using UnRollSrf. Sometimes it works, sometimes it doesn't. Also opened the Rhino 4 version I saved and tried UnRollSrf on original surfaces. Inconsistent results again. Didn't work on one panel the first time I tried but did on other panels. Tried again and it worked.

    Also checked Gaussian Curvature which is verly close to 0 everywhere on the original surfaces. Don't know what is leading to problems.
     
  6. Dean Smith

    Dean Smith Previous Member

    ok so you opened my file?
     
  7. DCockey
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    DCockey Senior Member

    Yes opened it. The same as what I got with UnRollSrf on my reworked surface. UnRollSrf on the original surface differed very slightly.
     
  8. M.Ezell
    Joined: Oct 2008
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    M.Ezell Engineer, PE

    Wow, guys. Thanks for all the input. I was away from the computer today or I would have answered sooner....

    I developed the surfaces a couple of ways. The plans for the canoe include a center mould that is removed and an aft and forward bulkhead. I took those sections and the bow and stern profiles by scaling off the lines drawing. I lofted it with developable surfaces on. I came out with a bunch of conics that didn't really match the sections and crossed the chines. I then tried connecting the edges of the hull sheets using interpolate curves and building the surfaces with EdgeSrf using two curves per surface. Using only two edge curves, I thought it should not create concave or convex surfaces.

    The upper sheer sheet unrolled fine. The bilge and bottom sheets wouldn't unroll. I was able to flatten them using smash, and flatten. I am using R5 beta for Macintosh, it doesn't seem to have squish or DevSrf.
     
  9. M.Ezell
    Joined: Oct 2008
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    Location: Portland, OR

    M.Ezell Engineer, PE

    Success - I think

    Hi Again. Okay, I looked at the hull with gaussian on. The plates showed uniformly green gaussian curvature with the range from -.1 to .1, green being zero so I just went ahead and used flatten. Here is the result. I will insert Dean's file and compare them more closely, but these look right. Thanks for all your help. The problem may have been that there is some convexity/concavity or a bug since I'm using a beta version. My work CAD system is Microstation. I will probably export the model and try using the flatten developable surface at lunch this week. In the mean time, my plans show the flat pattern for the plates. I have created a 2D dxf of them for my companies main sheet metal fabricator to cut out using his laser burn table. If all goes well, I will have the canoe built by summer.
     

    Attached Files:

  10. M.Ezell
    Joined: Oct 2008
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    M.Ezell Engineer, PE

    One more post and to bed. I inserted Dean's flat patterns onto my patterns. They are virtually identical. I think I got it. I'm still not sure why there was a problem as the gaussian curvature was so flat, but I hope to get an understanding as I learn Rhino better. All the cad packages I've worked with (about a half dozen so far) have had quirks. Oh... I also tried lofting from chine curve to chine curve with developable on. Unroll wouldn't work on the bilge and bottom. I think that is because the ends of the bounding chine curves for bilge and bottom come together at the ends. I think this may also be why unroll didn't work right. -Good Night.
     
  11. DCockey
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    DCockey Senior Member

    UnRollSrf worked fine for me on the lower panels. There isn't a generic problem with points at the ends.
     
  12. M.Ezell
    Joined: Oct 2008
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    Location: Portland, OR

    M.Ezell Engineer, PE

    Hi Again everyone. I got an email from McNeel - I had also submitted my question to them as well. They say it looks like a bug in Rhino v5. They were able to unroll it fine in v4.

    Mark-
     
  13. shellexpansion
    Joined: Sep 2008
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    Location: canada

    shellexpansion Junior Member

    hi guys,

    have you check the solid3dtech.com? they have a product to unfold the surfaces like hull. And it works well, in youtube, you can find the demo.

    eric
     
  14. Clinton B Chase
    Joined: Mar 2005
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    Clinton B Chase Senior Member

    Different design, similar problems

    Good discussion. I used DevSfc to work the panels on a 3 strake rowboat of mine (I too am learning). But had strange results with lofting with develop option.

    I lofted the GBD with a normal surface as well as a straight section surface. I extended the lines past the centerplane. I am risking my design here putting it up, but I need to figure this out, if you guys can help, I'd appreciate it.

    If I issue the UnrollSfc command and nothing happens at all (no messages, just "creating meshes....press Esc" but nothing flattens, is it safe to say my surface is not able to be unrolled?

    You can see in the model that the GBD is big but it will bend and twist into place on actual boat that was built from this model.

    This is a learning project for me, I hope it can help others. In the meantime I will try D. Cockey's approach extracting the edges and putting them through Dev Sfc again.
     

  15. Alik
    Joined: Jul 2003
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    Alik Senior Member

    This is an interesting issue... I always create surfaces by Loft/normal command in Rhino, based on two lines. And it always unrolls and works in material. Creating surfaces with 'developable' option often gives funny result on bottom plates at bow. So they question is what is mathematically correct and to what extent Loft/normal will work?
     
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