algorithmic modeling for Rhino

Minor updates and bug fixes to 0.8.0002 available for download.

  ● Added proper tooltip formatting for Expression Variants.
  ● Added more icon feedback to preview modes.
  ○ Fixed flat Box to Brep conversions.
  ○ Fixed Nurbs Curve to GH_Curve conversions.
  ○ Fixed a bug with lingering previews on disabled objects.
  ○ Fixed yet another bug with Curve offsetting.
  ○ Layers in the undo stack would still show up in the Bake Dialog. This is now fixed.
  ○ Fixed a bug in Sweep2.

David Rutten
Seattle, WA

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Replies to This Discussion

As far as question 1, I can't reproduce this - divide surface works exactly as it should. Is it possible the surface you're working with is trimmed inboard of its UV domain? the divide surface command will return null values if the division points fall outside the trim.
My Bad, Yeah the first one is not a bug it seems. I had Retrim ticked when i was rebuilding the surface in Rhino 5 after i had deformed it. Sorry
it's fantastic to be able to double click components to access the help for that item, but it seems impossible to get the help in this way for the items that are hidden when "draw all components" is not enabled. Is it possible to have this kind of double-click interaction function when the menus are open?
I opened a grasshopper file that I created in using 0.7..., but something's not right. The vb script component tells me that it does not recognize DocObjects.LayerInfo anymore. What gives?

Hi Ben
just use DocObjects.Layer ....DocObjects.LayerInfo is obsolete

Could it be that Min and Max are swapped for this component? (Both curvature and curvature direction). In the example above it says that Maximum principal curvature = 0. That seems unlikely for a cylinder. I looked at the directions in another test and they seem swapped too.

Zero is certainly larger than -2.



The sign of the principal curvature depends on the direction of the normal at the point of interest as well as the direction of the principal curve.  If the normal and the curve have an opposite sense the curvature is negative.



Yeah, this makes sense, and since nothing can curve less than Curvature "0", zero has got to be the Min Principal Curvature here, no?

No.  Curvature is signed based on the direction of the normal at the point of interest and the 'sense' of the curves direction so it can be less than zero.  So one of the principal curvatures can be negative and therefore less than zero and also the min. principal curvature which would make zero a legitimate max. curvature.  Certainly though the absolute value of the reciprocal of any radius will always be greater than zero but that's not curvature as we're talking about it here.  In the case of the cylinder if the normal is pointing toward the central axis then the curvature would be positive since the curve of the cylinder and the normal have the same 'sense'.  If the normal is pointing outward then the curvature would be negative since the normal and the curve of the cylinder now have opposite 'sense'.  At least this is how I understand it.  Playing around with the curvature component and a referenced cylinder I notice however that changing the direction of the normal from 'outside' to 'inside' has no effect on the output of the component.  Swapping the uv directions however does change the sign...hmmm?


Yeah I don't get it either.  It seems like the max and min curvatures should flip in the case shown in the screen shot attached.



Surfaces have a strictly defined normal vector definition. So if you flip the U direction, the V direction, or if you swap U and V the normal vector will be inverted.


Breps on the other hand have an override for the normal direction. A Brep Face is allowed to invert the normal direction of the underlying surface. This is so we can join surfaces into polysurfaces and have their normals match up without the need to flip directions and trimming curves.


I'm not sure but it could be that the current confusion stems from this brep-face-normal-override flag.



David Rutten

Seattle, WA






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