@chuanzhen said in Discussions about spline ik:
I read the paper and watched the video. The video is understandable and the paper is still obscure.
Which paper are you referring to? The RMF paper? It has a chunk of pseudo-code you can straight up copy.
The Parallel Transport method is useful, but using the control object to control the rotation of the joint (rotate around z) is still a bit unclear (in the picture below).
I am still unclear on what is intended on what is not in your pictures. Is the twisting motion of your chain of objects intended or not? It would probably be best, if you just would generate an image of what your algorithm currently gives you and then create a second image, where you have fiddled your objects by hand into the orientation, you want them to have.
The paper seems to mention some solutions such as (Animating rotation with quaternion curves) and (Fiber bundle twist reduction.)
I am still not sure which paper you are talking about. There are other algorithms, especially a lot of hacks for PTF, but at least I would say that RMF will give you the best results, while being relatively simple, and PTF (or a naive version of aPTF like shown in the video) will give you good results, while being very simple. You have also to keep in mind that these all are hacks, i.e. algorithms for imitating what humans would consider an aesthetical set of frames placed on a curve. In reality the normals and bi-normals of a curve will flip based on the tangency of that curve.