If you have two OnCircles, then you should try and use more mathematical based solvers as opposed to the "physical" solvers that you'll have when finding the intersections of pure NURBS curves. Unfortunately though, Rhino does not have a circle/circle intersector (I don't know why), so you'll have to do a little bit of juggling to find the intersection. Rhino does have a line/circle intersector, so if you first intersect the two planes of the circles to find a line, then intersect that line with one of the circles, you can get the intersection points. Both the plane/plane intersector and the line/circle intersector can be accessed through OnUtil.ON_Intersect. There are 11 different overloads for that function, so step through intellisense to find the one that you need. Remember that any variable that has ByRef in front of it will be information that you get out of the function. In this case filling out those values is the info that you need, not what the actual function returns (which is either an integer for the number of intersections or a boolean value).

Here is a part of my class in GH I hope it will help for easy understanding and use. Have a fun!
Lukas

Hi,

Following up on the suggestion to use a mathematical solution to find the intersection points,
here is a vb function that should work for 2 circles on the world xy plane:

'This is based on Paul Bourke's "Intersection of Two Circles"

Dim r0, r1 As Double
r0 = x.radius
r1 = y.radius

Dim p0, p1 As On3dPoint
p0 = x.Center
p1 = y.Center

Dim d As Double
d = p0.DistanceTo(p1)

Dim a, h As Double
a = ((r0 * r0) - (r1 * r1) + (d * d)) / (2 * d)
h = math.sqrt((r0 * r0) - (a * a))

Dim p2x, p2y As Double
p2x = p0.x + a * (p1.x - p0.x) / d
p2y = p0.y + a * (p1.y - p0.y) / d

Dim xPt1 As New On3dpoint()
xPt1.x = p2x + h * (p1.y - p0.y) / d
xPt1.y = p2y - h * (p1.x - p0.x) / d

Dim xPt2 As New On3dpoint()
xPt2.x = p2x - h * (p1.y - p0.y) / d
xPt2.y = p2y + h * (p1.x - p0.x) / d

ptA = xPt1 'A changed to ptA
ptB = xPt2


Hope it helps