Curve | curve intersection points not what expected

[Andrew_Albarez]

I am having a hard time understanding why my intersection point is not on the end of the surface. I have tried different approaches, but cannot figure it out. Does anyone know why I am getting this stray point?

curce intersection issue.gh (8.7 KB)

[Eef_Weenink]

Dear Andrew,

I could not see what you described. All points were spon-on the place you would exspect. Maybe something with preview? Resolution?

New for me was to use Curve to extract curves out of a surface. I would have used Brep Edges or Brep Deconstruct. And I do not understand the use of Cross reference? Maybe to get equal number of curves on the Curve | Curve component?

Just Graft one of the two lists will solve this. And Cull duplicates is nice to end with the 12 you see in the preview.

curce intersection issue_eef.gh (11.1 KB)

[inno]

@Andrew_Albarez

understanding

just for the stake of understanding, you are trying to intersect the outer boundary of each of these three surfaces:

with these seven curves curves:

crossreference is being used in order to account for any possible combination of those 3 boundary-curves with any of the the 7 other ones

those two points are generated as result of curve_A index 11 with curve_B index 11:

in particular, curve_A at index 11 is this green curve which travels horizontally, while curve_B is the boundary of surface at index 1, which has its top side running EXACTLY over that same portion of curve_A:

the reason why the intersection points are off, is because of Rhino tolerance: if you go to Rhino Options → Units and increase the tolerance from 0.01 (default value, in my case) to something much higher, like 0.00001

you will get this, where interestion points are actually placed at real intersections

[Andrew_Albarez]

@inno

just for the stake of understanding, you are trying to intersect the outer boundary of each of these three surfaces:

with these seven curves curves:

Yes that is correct. Weirdly when I increase the absolute tolerance as you did, I get more points!

Another thing is that when I recompute, without changing anything the points shift around slightly and in some cases the second additional point will leave, but the 1st additional point doesn’t -only moves left or right along the curve slightly. Strange.