Rhino 8 - SubD shape fitting with degree curve (continuous curvature)

SubD shape fitting with degree curve (continuous curvature)

In Alias Speedform there is an extremely helpful and cool feature to adjust the SubD shape.
You can select a range of edges and align them using a degree curve or adjust them using the degree curve. This has the advantage that you don’t have to move each point, face or edge individually by hand. Another huge advantage is that the result has a totally clean gradient with little effort. The degree can be determined for each curve. So the curve to edit can be very simple with 3 degrees or more detailed for example with 5 degrees.
The finer the mesh, the more useful this feature is.
Rhino really needs this feature.
Or even better.
In Alias Speedform you can use only one degree curve for a selection of edges. You could also extend this feature.
-It would be cool if I could adjust multiple selected edges with one curve in parallel.
-Cool would be the same principle with faces. If a selection of faces could be adjusted and/or aligned using a surface.

The video shows a selection of faces that is adjusted with a grad curve. (Alais Speedform)

The sequence of images shows the selection and use of the feature in Alias Speedform.

3 Degree Curve

5 Degree Curve

Adjust Edges with control points of the curve

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Not sure is what you need but in Rhino you can both use the soft transform or the align to curve. Different workflow but same result.

I see the power of Alias’ “edit by curve”.
also to have the “even distribution” option.

to do the same in Rhino, it would mean the follow (but not very practical) workarround:

select the edges in Question
(_join in some cases)
_rebuild (to the degree, and CV-count = degree+1)
this will be your base-curve

edit a copy of the base curve to the desired shape.
this will be your target curve

now use
_flow (copy = no, preserve structure = yes, stretch = yes)
to rearrange the vertices / edges.

the big pity about above workflow: _flow is claimed to support history - but does not do it for a subD-Vertex selection. (and also not for nurbs-cvs) - both wold be very powerful.

and the second pity: the above workflow shows, that the general functionality is there to do this nice editing…

align to curve is not very satisfying in this situaiton - the vertices will be set to the shortest distance on the target curve and will loose their distribution / spacing

see the follow simple example
left - flow, workflow as described above. (green - base, blue - target)
right - align

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Hello Skysurfer.

thank you for your answer. i know both tools.

softtransform is for me a completely different tool and very inaccurate.
the align to curve tool is helpful and can produce a good result. but it’s just not the tool i want to get to the target quickly and accurately without fiddling around.
what is missing from the tool is that i can adjust the target curve afterwards and the subd surface changes accordingly. then it would be quite similar to the tool from alias speedform. but still more cumbersome.

Hello Tom,

you understood what I mean.

"edit by curve from alias is a powerful tool without a cumbersome workaround.

I know the tool “align to curve”, but a bit impractical and it is not customizable. I can’t directly adjust the result with the CV points.

In this sequence of images you can see the problem that I change the curve, but geometry does not, even with history turned on.
This is exactly where the strength of the “edit by curve” tool from alias.

yes - looks like this is not possible.

cumbersome workaround:
keep the original curve
edit a copy
apply flow a second time (base = original, target = copy)…
not interactive … ;-(

Flow should work here, or even better, CageEdit on vertices, with a curve as the control - my guess is this is possible… I’ll ask.


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didn t manage to to this.
Prompt: select captive object !
no SubD’s CV selection possible

i 'll add it to my wish-list for advanced CV-Edit in this topic:

Unfortunately, none of the issues have been addressed in the current Rhino wip.

-No tool similar to “edit by curve” from alias / speedform.
-Align by curve still doesn’t have the possibility to change the result with the target curve (CV Points). you still have to repeat the procedure every time until the desired shape is reached.

Best would be both tools! something like edit by curve and align by curve improved. because both would have own small advantages.

@ rhino: please make at least one of both possible in rhino 8.
This would make SubD a lot more precise.


Hi Nik - realistically, I do not think this will be better in V8, but the items are on the list that should help when they are addressed
RH-75087 CageEdit: allow grips
RH-75088 Align: Support history


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see also here

Hi @nik.mvk! As @Tom_P suggested, you should check TestSubDEdgeMatch, a new test command in Rhino 8 WIP :slight_smile: . This test command should be able to help you fit a set of SubD boundary edges to a target curve. History is not supported yet, but we are working on it so that you can modify the target curve after and get the SubD match updated automatically.