Generating middle curves

Is there a better way to generate awkward curves like this (In Red, its for Y branch T spline)
There is only so much I can do with orient and using pull on a patch.

Centre curve position.3dm (170.2 KB)

Better in what way - method for creating the curves, shape of the curves, arrangement of the curve?

If the method then how did you create the curves in your file?

Yes, sorry.

I need it to be aligned so it has a smooth transition when making a surface.
Like extracting a middle isocurve on a rectangular sweep.

I dont want it to dip up or down, and doing it by eye with such an organic shape is too imprecise.

I just thought there might be a better way of doing it than the way I explianed in my first post.
ie using orient 2 points with the orange border curves and moving them to a different position, or making a patch from the orange border curves so I have somthing to pull / project onto.

From each surface extract isocurve.
For one of opposing isocurves blendcrv.
Make a point on the curve where you want the intersection.
Blendcrv to a point from one of the isocurves.
blendcrv again to the created curve to the opposing isocurve.
Repeat for third set.

Did ask once as wish that blendcrv can stop at an intersection. Not sure when that will happen…


Thanks for the info. Yes an intersection blend would be realy useful.

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It would be useful, in my opinion, to create an ad hoc command that could generate this condition for each surface with one click.
Very useful for example making better ‘patches’, with additional guide curves.
be useful? Would you add to the wish for Rhino v7?
I would like to know what Pascal thinks of it, it might be an idea for Rhino:thinking:

Yes it would be useful.

Having blendcrvs stop at the intersection when manipulating the curvature.
And, blending curves with having additional reference point to include in the curve would be nice.

@Toshiaki_Takano What does this mean, exactly? Do you have an example?

@Simon_Jackson - without the surfaces it’s hard to see what curves to build but, if you can guess at a point, then BlendCrv from the point to the surface edge (Edges option) followed by matching the results at the convergence point to the opposite curve for tangency, Average checked and ‘Preserve other end’ set to Curvature, can be one way to go.


Hi @pascal

When doing blendcrv to create a set of curves to patch up multiblends,
it’d help if the blendcrv’s curvature control would stop at where a intersection between another curve meet.
Also useful for creating tips of organic objects with networksrf.

Want Intersect Sample.3dm (283.2 KB)

Hello - Ok, so, interploate the blend through a point, really, is what this is, correct?


Sort of,
But, since I won’t know where to place that point when making the second curve I’d like to interpolate using a curve, and let rhino take care of the optimal curve.
-> I don’t want the created point to add additional curvature to the blend curve being created. In case of interpolating using a point on the curve.

Does that make sense?

Below is a bit drastic, but if a point interpolation, something like this to some degree probably happen. like an extra S curve somewhere.

It’s not easy, it depends very much on the geometry of the curves edge. I thought it was simpler…

At least a function that allows to stop at the intersection seems uesful.
The blendcrv to point then doing another blendcrv to create the crossing curve would produce a less simplier curve.
Blendcrv going from one surface to the other would be smoother than making a point to connect to.
Though the third curve will need the interpolation through the intersection point.

If somene can make algorithm to get the optimal point for the curves to join up for blendcrv to that point for smooth surface…

Was asked for a surface pic.
WOW this thread got a lot of attention! Thank you everyone for your insights.
I am experimenting with TS as a bridge between surfaces.