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Spline Lathe Creating Vortex on "Glass" Surface

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Hi guys, hoping someone can help me understand how to fix this issue I'm having. 

 

I'm rendering out a glass fishbowl that I made using a lathe object, but I'm getting this weird vortex effect on the material up top.  Obviously when a material is added to a sphere this doesn't happen, and in polygon mode they appear to have similar meshes.  I don't have enough experience with UV mapping or modeling to really know how to get around this, and it's making my life very hard at the moment...

 

I'm attaching the project file as well as the spline/lathe vs sphere tops to illustrate what I'm talking about.  

 

Any advice would be greatly appreciated, thanks!

lathe.jpg

sphere.jpg

Glass Bubble.c4d

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It's because you haven't made the spline properly for use in a lathe. The center-point must remain open, so the vertical line here needs to go. Just untick 'close spline' in the options to make that so, and if that removes the line in the wrong place, then you can change that by selecting the right point on the spline, r-clicking and choosing 'set first point'.

 

image.png.cbaebf0f485752af911b69730f2dd738.png

 

CBR

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  • Ah, thank you!  What is the easiest way to do that?  I've already closed the spline and when I try and disconnect those points the bezier goes crazy.

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    No, you need that spline UNclosed. I just checked in your file, and that should be all you need to do to fix this.

    image.png.0a30da3c2474c5fb030126544b21fc4f.png

     

    CBR

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  • Firstly, thank you for your help, I really appreciate it! 

     

    I've opened the spline and it does seem to have improved the warping up top but it is still there.  I've made sure my points are lined up so there would be no discrepancy there, but I can't seem to get it smooth like a primitive sphere object.

     

    Check out the attachment (spline lathe on the left).  Anything else I should try?

     

    open_spline.jpg

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    Yes - I did already discover this, but was monster busy with client work yesterday so didn't have time to come back.

     

    There is something else wrong with your spline that causes this issue - initially I suspected that the centre spline points weren't at position XZ 0,0, so that is one thing to check. But in the end I deleted your spline, made a new one from scratch and was able to get a perfect deformation-free result, so there must have been something dodgy about the original introduced somewhere along the line. I didn't have time to investigate what that was.

     

    Here is the correct workflow for adding precisely the right type of spline to make this work...

     

    1. Get circle spline, and make editable, which will look like this.

     

    image.thumb.png.dce014fb20059745cf04d39fd0560e9f.png

     

    We only need half that shape, and only the upper proportion of 1 half to go in our lathe. But we can't just delete any points, because there are only 4 control points in this form at the wider editing level) that will compromise the circular shape if any of them are removed. So to solve that we need to set the interpolation correctly (default of Uniform / 8 is fine). 

     

    But then we need to access that interpolation, so r-click the spline in the OM and choose Current State to Object. Now your new spline will look like this, which is much more suitable for the task at hand, because now we can delete segments without ruining the shape. At this point you can delete the original spline and just keep this copy.

     

    image.thumb.png.fecd631e218c813489b61f3a453f5acf.png

     

    2. Delete the segments we don't need so you get this.

     

    image.thumb.png.819b5de68110555e6abf285472c45864.png

     

    Make sure that the centre point at the top is at ZX position 0,0 in the coordinates manager.

     

    3. Now, with he spline selected and in points mode we can use create outline to get the inner surface. by dragging left in the viewport, for this result.

     

    image.thumb.png.9712b6b41c4388f574d15b5fb00e2381.png

     

    This is fine, but the selected point above isn't at XZ 0,) so you need to make it so before continuing...

     

    image.thumb.png.fd7a98fff5f473d8c5d83913fc431700.png

     

    Here is that done, and now with Close spline unticked to leave an open end there, which is what we want.

     

    4. Now we can add the Lathe, so with the spline selected, hold Alt, and add one, which will auto-parent it to the spline perfectly aligned, as it needs to be.

     

    image.thumb.png.dea6d04a588f3b34b36edfca153799be.png

     

    Now we can turn the Lathe on and get a perfect, deformation free result.

     

    Hope that helps.

     

    CBR

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  • Thanks so much man, this is super helpful! 

     

    I did make sure the center points were at x,z 0 but it must have been the curve to the next point that was throwing some deformation.  I'll start with a perfect circle and go from there, didn't even consider that. 

     

    Thanks again, you're a life saver!!

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