No centroid on a few crvs from contour.

Hello Everyone!

I am working to get a consistent contour shape out of a pretty nasty model of a head. Problem is, some of the curves don't get a centroid when I use area-component.

It says two warnings:

Crv must be planar for Area calculation - They are all planar. Have baked them and checked.

Crv Area mass properties could not be solved - what does that mean and is that my problem? if so, is there a solution?

I'll upload my files for you to see.

ps. the rhino file with the head model was bigger than 5 MB so you can find that here:

http://expirebox.com/download/2763a63d1a6a1e7feeefb0c89afd582a.html

All help is appreciated!

Thank you.

Attachments:

ask grasshopper - no centroid.gh, 13 KB
pic no centroid.JPG, 110 KB

Replies to This Discussion

Permalink Reply by Danny Boyes on August 19, 2014 at 3:24am

I would say that Grasshopper is failing to Convert the Curve into a Planar Surface and therefore failing to get a centroid (second warning msg) you could try using the Polygon Center component or divide the curve with many points and find the average.

For the first message you could try to project the curve onto a plane set at the start of the curve and then calculate the centroid with the area component

Permalink Reply by Olof on August 19, 2014 at 3:35am

Ok thank you. Perhaps that is the case. When I bake them rhino does however succeed with creating a planar srf using the _PlanarSrf command... But I don't know, maybe that is different?

I will try and see if it helps with the many point idea. Thank you...

If that doesn't work I'll try the other way you proposed.

I'll let you know how it works out!

Permalink Reply by David Rutten on August 19, 2014 at 3:53am

Planarity is a tolerance based operation. Whether or not a curve in 3D is planar usually depends on the accuracy you care about. If Grasshopper and Rhino are using different tolerances (they typically shouldn't, but it's possible the code is wrong) then a curve may well evaluate as planar in one and non-planar in the other.

I can't test this as the file you posted requires a Brep from a 3dm file which you didn't include.

David Rutten

david@mcneel.com

Permalink Reply by Olof on August 19, 2014 at 3:56am

Aa ok! Thank you.

The 3dm file was to big to upload here(EDIT: this 'here' refer to this forum) (8mb) so I put it here:

http://expirebox.com/download/2763a63d1a6a1e7feeefb0c89afd582a.html

Permalink Reply by Arend on August 19, 2014 at 7:15am

Seems weird, but projecting the curve to it's own plane does seem to fix the problem.

Attachments:

askgrasshoppernocentroid-project.gh, 8 KB

Permalink Reply by Olof on August 19, 2014 at 9:43am

Yeah, great Man! thanks!

Thanks to all of you. This is now resolved!

Permalink Reply by Arend on August 20, 2014 at 1:50am

NB: If you just need "something in the area of the centroid", the center of the boundingbox is usually (boundingbox+evaluate box) can be much faster than calculating the area.

Permalink Reply by Marcola on February 13, 2016 at 5:16pm