Measure Radius of Surface or Solid Fillet

Rhino
1

Is there a way to click on a surface or solid fillet that does not have a perpendicular cut. I usually just throw a iso curve on it, then measure the curved fillet. Just seems like there should be an easier way and I can’t find anything in the search.

2 
_Curvature

is technically what you re after, but it will output “inverse radius” = curvature. 1/r = c
combined with inline calculation it is acceptable for many workflows.
not a 100% solution - kind regards -tom

3

Hi @Tom_P

Is this any easier than creating an isocurve first and using radius? Don’t we still have to use radius after the curvature command and measure the created curvature curves or do the math you describe? Seems Rhino should report the radius at the curvature point too at the command line and maybe an option to create a radius curve like in the radius command.

RM

4

… and local curvature might not be the same - see this simple example (red/green = iso, blue = curvature)

image
image1764×1539 507 KB

it depends a bit - the featback in the commandline might be:

Surface curvature evaluation at parameter (36.673, 7.34208):
  3-D Point: (297.442, 36.673, 96.6792)
  3-D Normal: (0.744229, 2.34621e-16, 0.667924)
  Maximum principal curvature: -0.1 (-0.667924, -3.15997e-16, 0.744229)
  Minimum principal curvature: 3.36991e-33 (-3.68984e-16, 1, 5.98688e-17)
  Gaussian curvature: -3.36991e-34
  Mean curvature: -0.05

-0.1 = Radius 10mm
if you need the radius somewhere as input type 1/0.1 and you’re done…

but i agree “radius” is more human-accessible.

5

After looking at the solutions that people have given and put more thought into this, this would be a difficult thing to do. If you had a fillet running around the top of a box that has filleted edges, then how would clicking on a point on the corner fillet be determined? Is it supposed to give you a perpendicular radius to the fillet, or a parallel to how it’s running?

Don’t get me wrong, I would love to see a solution to this, or to have it in the next version, but it seem like there might be too many variables to have a straight forward answer. But by no means, please keep chiming in if you have a better solution that what I am already using.

6

Script solution:

7

Maybe this is helpful:
show_min_radius.py (1.8 KB)

It will show the minimum radius of a surface at its midpoint. So not suitable for double curved surfaces or variable radii fillets:

2 Likes
Lack of persistent 3d dimension tool
8

Thanks, this is pretty much what I was looking for.

9

Hi @Gijs

Awesome work! I like the way you did this with the text dots and display it’s great that it reads a whole polysurface including flat angled surfaces.

Thanks for your expertise,

RM