Why do people fear splines?

kevin_quigley

Splines. Yes. Used every job, every day. In SolidWorks style splines has replaced node based splines (but of course you can show the control cage for a node spline in SolidWorks and edit a node spline using the cage...you just can't dimension to the cage).

but the real skill is in 3D splines and this is where we default to Rhino or Ashlar-Vellum Cobalt or Shark FX. Few heavy duty MCAD systems have splines anywhere near as good as those three. Then there is Alias of course...

two point splines or conic curves are great but they cannot deal with every form, and in my experience building up a complex profile from multiple splines by using contrainted joints is a recipe for downstream failure and poor quality surfaces....top tip...keep your surface drive curves single!

billy2

Using splines Tip#2

When you offset a line, you get a line:


When you offset an arc, you get an arc:


When you offset a spline, you get a spline (kinda):


When you offset an ellipse, you get ?



https://youtu.be/TyRXzYpkYx0

mark_biasotti

"Surfaces are only as good as the curves that create them."

billy2

Frank Gehry's Bridge: an example of splines





There's a million screws and they missed one. Probably needed a better cad system to get the holes to line up correctly:

michael_stalls

Im not afraid of splines! this is the baseline configuration/onshape trial run i did for a custom aerobatic aircraft we are designing for a client. the fuselage is lofted from spline crossections. A tedious process but it produced good results



the nose cowl was particularly complex.It was made from 10 spline cross sections

As can be seen i cant seem to use the shell feature on the nose cowl.
the model itself is huge and bit messy. hopefully ill be able simplify the next version

mark_hubrich

I couldn't have done this job without splines I like them. Especially nice when you utilize digital fabrication and don't require dimensions for some poor fabricator to try to layout. Let the machines do all that time consuming work  

jlieber

That is pretty awesome, thank you for sharing this!!

billy2

So I submitted a fix-it ticket for my approximated ellipse and it didn't go well. Turns out we couldn't duplicate the issue. Turns out creating the geometry at the origin seems to trigger something on my computer. Everywhere else it's fine, only on mine was the origin special.

4 mirrored splines in 4 different quadrants (forget the center one):

billy2

Love the examples, thanks for sharing....

mark_hubrich

billy said:

Frank Gehry's Bridge: an example of splines





There's a million screws and they missed one. Probably needed a better cad system to get the holes to line up correctly:

They missed one screw only or one at each panel? Do you know what was used to model this? It probably wasn't Tekla or SDS2. I have had great success using D-Loft for Rhino. This project you show is only a mile south of mine

DriesV

mark_hubrich said:

billy said:

Frank Gehry's Bridge: an example of splines
...

They missed one screw only or one at each panel? Do you know what was used to model this? It probably wasn't Tekla or SDS2. I have had great success using D-Loft for Rhino. This project you show is only a mile south of mine

Frank Gehry... so there's probably some CATIA involved. :-)

Dries