Well, exhausting answer. I understand a theory. But I'm still a little bit in a stew when I compare a result from planar component (planarity boolean and deviation number). A deviation is app. zero (E -7^10), but result of planarity dont correspondent with this results. Why?
link of screen: http://grasshopper3d.googlegroups.com/web/planar%20curves%20-%20deviation%20test.png?hl=en&gsc=SbsaaQsAAAD9eVjlhhOyJJVQcOC4oTFX Joach On Mar 8, 10:54 pm, David Rutten <[email protected]> wrote: > Hi Joach, > > The intersection between two surfaces is usually a very complicated > curve. If there exists a nurbs curve which represents this > intersection perfectly, chances are it will need a massive degree > (think 30) and an enormous amount of control points. This is why we do > not provide those curves as results. > > Internally, Rhino calculates the intersection to a much higher > accuracy than you request. The thousands of intersection points it > finds between the surfaces are fitted with a single nurbs curve. This > nurbs curve is not allowed to deviate from the intersection points by > more than the tolerance. So, even if all the intersection points are > on the same plane, it is possible that the fitting curve will deviate > from this plane by a maximum of <tolerance> units. > > When we test for planarity, we also need to pick a tolerance. If you > have a flat curve with no z-elevation at all, then it's obviously > flat, but if you rotate the curve so that the plane is tilted along > each axis, then the very accuracy of floating point numbers will cause > it wobble, ever so slightly away from the ideal plane. > > The planar component in Grasshopper is set to maximum accuracy. I'll > adjust it to only operate within current Document Absolute Tolerance. > Incidentally, the planar component will output the deviation from the > ideal plane. You could also compare this to a numeric value and so > decide upon your own tolerance within Grasshopper. What is the > deviation that you get? > > -- > David Rutten > [email protected] > Robert McNeel & Associates > > On Mar 8, 10:06 pm, joach <[email protected]> wrote: > > > It wasnt visually? I used planar component for fast test and there > > isnt possible set a tolerance. When I used VB.net definition > > (.isplanar) and your tip its work perfect. Thanks for you David for > > your quick answer!!! What exactlly is mean by tolerance? > > > Thank for GH, a special with vb.net component it is so strong tool. > > GOOD WORK!!!!! > > > Joach > > > On Mar 8, 9:38 pm, David Rutten <[email protected]> wrote: > > > > Hi Joach, > > > > if the intersection tolerance is less than the planarity test > > > tolerance, curves will appear to be non-planar. Or are you getting > > > visually wacky results? > > > > -- > > > David Rutten > > > [email protected] > > > Robert McNeel & Associates > > > > On Mar 8, 9:26 pm, joach <[email protected]> wrote: > > > > > When I make a intersection of two Breps (first is from onNurbsSurface, > > > > second is a plane surface define from a frame of curve, function > > > > pointAt(w = 0) ) result of this operation is a array of onCurve. How > > > > is possible that curves arent planar? tolerace of intersection of brep > > > > is set to 0.01 > > > > > Any idea? Thanks > > > > Joach
