Hello,
I’m trying to bend the crest rail of a chair back. In top view I see a preview of what I’d expect but when I commit, the bend is mostly reduced.
I’m somewhat new to modelling these compound curves and wonder if I’ve taken a wrong strategy somewhere? Would this be better modelled as a subdivision? I’m not sure how to proceed from here.
BeidermieierChair.3dm (3.7 MB)
How much experience do you have modeling objects in Rhino? Do you have experience using other 3D modeling software?
What did you do to obtain the preliminary bend in the top image?
Are you trying to model the chair in the photo? The crest rail of the that chair is a separate piece from the uprights. Also that crest rail is curved its entire width, not only at the ends.
Or are you trying to model a different design only the ends of the crest rail bent?
Thanks for the response
I have 50 days remaining on a rhino 8 trial. I’ll likely make the switch.
I’m proficient in Sketchup, and once upon a time Vectorworks, with not so much time modelling compound curves like these.
The preliminary bend above is with the bend command, which is new to me. The spline start and end are visible in the image. When I commit the command, the crest rail springs back leaving only minimum bend.
Here’s another screenshot:
Things got deformed a bit as I’ve worked through the various curves, but I’m not unhappy with where things stand.
I introduced a split as shown above thinking I’d bend the crest rail and a portion of the stile and then blend_surface back into the lower portion of the stile. I’m working with the assumption I’ll mirror the leg/stile/ and half of the crest rail. I was attempting the bend the rail from the vertical centerline rightwards to let the scroll-like flange hug a sitter’s back. This is somewhat visible in the initial side view I posted, and here:
My workflow was:
-draw profile curve
-project profile curve to a vertical curved surface representing the overall front to back shape
-trim and extrude.
-split the extrusion with another curved surface representing the back of the assembly.
then I intended to bend, then blend_surface back together… mirror.
I’m learning as I go here and using some brute force and some new commands…it’s an exercise. The design is a bit forgiving I think. I hoped I’d learn how to dial things in after I got the basic form.
It works fine on my side, and made a video for your reference.
Bend.3dm (1.2 MB)
I can’t recreate that. It continues to spring back.
You don’t generally model something like this by “bending” it like it’s real wood or something, it’s insanely limiting, you just take the surfaces you’ve already made below and point-edit them. Freeform point-pushing is a foundational NURBS thing and the Level 1 and 2 Training that come with Rhino do get into it a bit.
I downloaded and tried your model Jessesn. It worked fine.
I noticed you grouped the geometry and deleted layers. I ungrouped, ran the command, and it worked as it should.
Not sure why?
When running the Bend, pls try not lock the second references point onto the object.
No luck even when locating 2nd ref point outside of object.
Is my file corrupt? I tested you Bend.3dm file and it worked fine.
Then I imported you model’s geometry into my model and it did not work. See below:
No. It was is not turned on. I don’t understand how this fits into the bend command not working?
Hi @Thomas36,
After you have selected the spline, turn off OSnaps before starting to bend. Bend sometimes clings to OSnaps in unexpected ways. Does that help?
Regards
Jeremy
Hi Jeremy,
Turning off Osnaps after setting the first spline point worked. I can bend now without issue.
Thank you for the help.
okay.
The bend issue has been solved but to your point, I’m unsure how to marry the bent crest rail with the unbent stile, so maybe my strategy is misguided.
they are trimmed surfaces and adjusting the control points results in unsmooth transitions.
If I’m starting with a 2D profile curve when and how should I introduce the 3rd y-axis dimension curvature? While it’s still a curve? or after its converted to a surface?
What’s the best way to transform a 2d profile curve into a surface that can be smoothly altered in the 3rd axis?
okay, I am and I will, and I realize I’m moving to a solid object too fast and without enough controls built in, but I’m finding it difficult glean and devise an approach for my own exercises while simply reading and copying the training guide examples.
a little more concrete guidance would be helpful.
