So I have an inside oval and an outside oval and I want to calculate/draw a curve that starts from the green point on the inside oval and spirals out to meet the blue point on the outside oval. I’m not really sure where to begin though. Can I do that within Rhino or should I use grasshopper?
please post a file to start from which makes it easier for people to help, i had to rebuild something similar which adds to the time i could be using for trying to figure something out.
also what exactly do you mean by spiral, one continuos euler spiral? might not be so easy with rhino only, some smart guy might figure something out in grasshopper, but that is as far as i can help.
the issue here is that you are trying to pseudo spiral against this race course like shape basically following along but also with its own mind sort of thing which i really am not sure how to express, but you kind of need 2 definitions while one is contained within the other.
below 2 suggestions
start with these 3 curves and use sweep2 with option add slash to straighten out the iso curves, maybe at each kink and mid point to calm it down.
extract the isocurve with the direction flowing around the surface in the midpoint
now create a surface that has the same width as your race course (i just call it that now) and the length from your iso curve. use the result as your base surface, there draw a diagonal line and use FlowAlongSrf.
the result creates a curve that continuously moves from one side to the other (more or less) along the actual shape which does not create an actual spiral, but as mentioned above that might be tricky to get right.
to make it a bit smoother, use divide and create maybe 30 points, use CurveThroughPt to redraw the curve with the contro point option, set to a high degree, now it looks a bit more like what you might want.
a different approach also very fiddly, draw two curves like here in orange, turn on history and use arc blend with alternative option, now turn on the points from the orange curves and edit the tangencies to your liking till it resembles what you might want.
Thank you for your help. The result you got in the first suggestion is exactly what I’m looking for, though flowAlongSrf doesn’t seem to be giving me the same result. I’m assuming I would set the diagonal line as the object, the straight surface as the base surface and the curved surface as the target? When I do that it just puts the straight curve on the target surface.
you might have the rigid option checked during flow
that would be correct otherwise yes.
Wow. There it is. Thank you!
so did you get the Flow running?
if you prefer the grasshopper solution use the grasshopper tags the next time. others might not be wasting their times then.