Rebuilding digitised curves


#1

i am having a bit of problem with rebuilding curves

i digitise a lot of components with a microscribe, being able to use the Osnap is a big advantage now, so thank you for that.

i use the sketch command within 3-D Digitising and then the rebuild curve command

in the first few versions of rhino WIP the rebuild curve command worked smoothly in the last 3 versions ( i think) the tangent of the curve seems to be controlled by the first 2 or 3 points in the curve at either end rather than an average through the curve?
As cmm arms can be a bit random at times is there a way have an option for averaging the tangent at the start / end if the curve?

regards

Richard


(Brian James) #2

Can you post some of your curves? Also, are you using Rebuild or RebuildCrvNonUnifom?


(Pascal Golay) #3

HI Richard - that is correct- the tangent direction of the original curve is maintained in the rebuilt curve, and yes, that is new. Usually it would be a good thing, but I guess not always, I’ll see if we can handle it differently - make it optional or something. Can you please post or send me a couple of curves for which the current results are not desirable, so we have a good example for the developer?

thanks,

-Pascal


(David Cockey) #4

Not good Actually very bad. :fearful: Make maintaining the tangent direction an option,

Attached is an example of using Rebuild to fit a curve to a set of noisy points. Step 1 is build a polyline through the points. Step 2 is Rebuild as degree 3 curve with 11 points. V5 Rebuild gives a much better fit to the polyline near the ends than V6 Rebuild.V6 Rebuild Undesirable 2.3dm (192.7 KB)

I can understand that sometimes maintaining tangent direction at the end points is desirable. So would the ability to maintain curvature. Why not make both an option when specified number of points in Rebuild result is sufficient.


(Pascal Golay) #5

Yep, got that, thanks.

https://mcneel.myjetbrains.com/youtrack/issue/RH-37045

-Pascal


#6

sorry not been near a pc until now

looks like you have it covered

Many thanks