https://github.com/mrdoob/three.js/blob/master/src/extras/core/Curve.js
I know this API, but it’s a far cry from ArcCurve functionality
Can you be a bit more descriptive as what “far cry” means? What are the specific functionalities you would like to see added? If they aren’t supported, then this can be a feature request, but as we have a lot of other functionalities to implement it won’t be immediate. Of course, since we’re an open source project, we would welcome PRs adding more curve functionality. 
@wudao as yesterday, please bear with the work of the community.
As it is all open source, if you really need a feature, you can contribute it
What you are looking for is probably Arc2
Thanks to the functionality of Babylon, there are many more material features than three. JS is powerful, but the basic components and apis are not three.JS is rich, such as the ArcCurve class feature I mentioned above
The three.JS docs say that ArcCurve is an alias for EllipseCurve, so are you saying you’d like to have an ellipse drawing function?