Need Guru to smooth a Rhino Chair!

[Grant Nelson]

Hi All, I was hoping that a Rhino expert out there might help me out. I have a shape, where I want a smooth rouned corner, however, no matter how I try I can either not get a nice smooth transition, or the edges of do not meet smoothly ... it would be great is some great guru could try this out, and explain how I can begin down the path to their level of greatness!

The file is attached, and I am: filleting the top edge by 5cm, the top side edge by 2cm and the sharp side edge by 1 cm. Then I want the upper left corner to have a smooth (rounded) transition with all sides

[Chris Ostlind]

Are you talking about the transition between the chair back and the side bolster/arm rest? I see two different radii for the top and bottom ends of the back, but no real smoothness issues.

Is there a reason why you prefer to present this model as a Rhino 4 file?

[Hans Friedel]

Rounded corners can be a pain in Rhino. sometimes it woorks but mostly not.

best way is if you draw the start and the end curve. And ad two rail curves on the surfaces you would like to make rounded. Than use the 2 rail comand. An if needed match the surfaces.

Also rather cool if the two rail curves meets you can use a point as last curve

Hans

[Grant Nelson]

Chris, I am talking about the forward upper left coner of the back rest of the chair - I want to fillet the forward upper edge with R=5, the left upper side edge with R=2 and the sharp forward vertical left edge with R=1 (cm by the way). This I can do. But where the three meet after the fillets I get various endings which do not lend themselves to say, making surface with edge curves, or patch. It appears that first some triming of the ends of the fillets is needed, but when I try that, I can still not find the right surface creating commend to make a smooth corner that transitions smooth from all the sufaces. So I was wondering if some guru could take the challenge on, and explain how it was done...
There is no reason that it is Rhino 4 except that this copy came back from a friend who (un-successfully) tried it out for me.

Hans, I tried your suggestion which offers some nice possibilities to fillet cleanly, but it still leaves the overlapping intersection of sweeped curves in the corrner that have to be trimmed (alway a pain, as sometimes trim works sometimes not - I presume due to tolerances) and you still have sharp edges or a hole in that corner that I want smooth...

Thanks for your help so far thought!

[Chris Ostlind]

Hi Grant,

Have you tried posting this question with file at the Rhino Newsgroup?
http://news2.mcneel.com/scripts/dnew...er&group=rhino

Lots of users there who are far more sophisticated with Rhino than am I.

[Grant Nelson]

Chris, thanks... I spend some time trying to find a site like that with Google (also from the Mcneel site) and never found a good one like this seems to be! If I get any good replies, I will post the results here...

[Raggi_Thor]

I'll take a look at it tomorrow, even if I'm no guru :-)
This is not only a modelling problem, but also a manufacturing problem.
In many 3D solid modellers the corner is nice and round if you fillet the three edges in one operation, while there is one or more sharp edges if you do it in several steps.
As I see it, the fillets with constant radius have to stop a given distance from the corner, depending on the radius. This leaves you with a hole to fill, where the edge consists of three arcs and three lines...

[Grant Nelson]

cool, yes, that sounds good - I am curious if you can get smooth transitions from all the surrounding surfaces... my attempts alway seemed to have bumps at the boundary, and the Zebra check also showed discontiunities... but maybe that is more a problem of my lack of understanding how to view these, and the settings I have for mesh, etc. and my somewhat limited graphics card... don't know...

[Raggi_Thor]

Sorry, tomorrow came and went and is no yesterday, I'll have atry on monday :-)

[Raggi_Thor]

I don't know if this is what you want,
but if you fillet the surfaces first, then the corner on the blue surface and then fillet surfaces again, then you can make the last surface with EdgeSurf.

[Grant Nelson]

Hey Ragnar, Nice! I tried it my self and could do it, but had to also trim off some of the fillets first. I still find a small smoothness discontinuity, most evident at the transition from the vertical fillet to the new corner surface. Am I being too picky, or is it real and is there a way to get ride of it...
Grant

[Raggi_Thor]

You can try MatchSfr and MergeSfr, then you should get a more continuous curvature. When you do a fillet, the curvature suddenly goes from zero to a constant radius. With Blend and Merge it's more gradually.

How picky you should be depends on what you will use it for. If it's for cnc machining with minimum manual finishing, maybe it's worth while to spend more time in Rhino first?

[Raggi_Thor]

I forgot:
Often you have to use FilletSfr to trim the flat surfaces, then delete the fillet(s) and make some adjustments before you fillet again. In this case I filleted first as you said with R= 1 , 2 and 5, then deleted those fillets and rounded the corner on the blue surface before I filleted again.

I used DupEdge to make the blues surface with a round corner, deleted the original surface, filleted the edge, joined and built the new blue surface with PlanarSrf.

OK I often write Sfr when I mean Srf :-)

[Grant Nelson]

Thanks again - very useful details / tricks! And no problem with Sfr - I did not notice - probably I am a bit dislectic... (have to blame my poor spelling on something...)

g.

[Raggi_Thor]

I found this today, and remembered our discussion :-)

http://offbroadway.blogspot.com/2007...ode-model.html