T-Splines Tangent Handles

[felix_star]

Hello everyone!
T-Splines are potentially a truly amazing technology! You can create shapes that are difficult to achieve with other CAD systems, even with just tangent handles! 😉 Unfortunately, they're very very difficult to manipulate: you can't enter numerical values ​​for precise point placement, and snapping doesn't work very well either... 😕 I suggest to the development team pay more attention to these tangent handles because they're very very useful to design perfect shapes! 😉
Bye,

Felix 😉

[adam.helps]

Thank you for the suggestion. I understand how numeric input would work for tangent handles. I also understand how snapping would be useful for control points. I am wondering in what situation you'd expect tangent handle snapping to be useful--could you go into a little more detail on what you expect that workflow to look like? I want to make sure I've understood what you are trying to achieve.

[felix_star]

Hi Adam and thanks for your reply!
I've prepared an example with one of the most difficult shapes to create with CAD systems (without using trimmed surfaces, thus accepting tollerances...): the famous "Y branch" shape. T-Splines technology can solve this problem without having to trim the surfaces. Many CAD systems have introduced Sub-D, but none have the same capabilities as T-Splines, first for the T-junctions and then for manipulating the tangent handles (in other CAD systems, the curvature at the edges always goes to zero, even when you don't want it!). I've attached the workflow sequence using some files. Finally, when I want to achieve G2 continuity also towards the straight part of the Y-branch (joined and patched T-Splines), I can't manage the snapping (edge surface ​​points and tangent handles) to any line or point... 😕
Kinds,

Felix 😉

[felix_star]

I'm attaching the file "T-Spline Y branch 10.f3d" because I suceeded to achive what I wanted, following another way: T-Splines are great! But I still think that is necessary to improve the capabilitues to manipulation of the the tangent handles. I challenge any other CAD system to do the same with their Sub-D. If you look well, the top and bottom are perfectly planar! This is not possible with the Sub-Ds of other systems... 😉

Felix 😉

[TrippyLighting]

I believe the capabilities you are seeking (proper curvature and better control) are already present in Autodesk Alias, where the T-Spline technology was used to achieve such things. Don't get sidetracked by the "Subdivision" terminology.

Unfortunately, the insane price point puts this out of reach of mere mortals.

[felix_star]

Hi Trippy, thanks for your message!

I tried the educational version of Alias, but I don't remember these features. I think T-Splines were only used for SpeedForm for Alias.

Felix 😉

[adam.helps]

@TrippyLighting Alias is doing something interesting. They are using T-splines, but they don't allow T-points, tangency handles, or non-uniformity (effectively using the T-spline as a subd model). To manage tangency, they instead have a more complex crease system that allows for various sliders to control the crease's behavior. I believe that lets them do more than a typical subd crease, though I don't know enough detail to say exactly what the capabilities are. So it's technically T-splines minus some capabilities but then with some other capabilities layered on top.

[TrippyLighting]

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@adam.helps wrote:

@TrippyLighting Alias is doing something interesting. They are using T-splines, but they don't allow T-points, tangency handles, or non-uniformity (effectively using the T-spline as a subd model). To manage tangency, they instead have a more complex crease system that allows for various sliders to control the crease's behavior. 

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The way I interpret that is they have a weighted crease!
Can you confirm that?

I would love to have a weighted crease in Fusion T-Splines! 

[felix_star]

Hello @TrippyLighting, but do think is so important to have weighted creases when you can obtain, more or less, the same thing adding edges to the polygon cage? 😉

[TrippyLighting]

I like options!

I very often model with weighted creases in Blender, as it allows me to judge the final form while still modeling.

Adding edge (support) loops adds geometry, which makes modeling very cumbersome.

Changing the weight of a crease is much quicker than sliding edge loops.

When I am happy with the overall shape, sometimes I replace the weighted creases with edge loops.