When the deformer is initially placed onto the curve, you must compute it's U coordinate 'U' on the curve as well as the U coordinates of the bounding knots (u1, u2). You then compute the ratio 'r' of the deformer's position within those bounds by performing a linear interpolation:
r = ( (U - u1) / (u2 - u1) ); and store the result off to the side for later use (repeat per deformer). This works because the relationship is independent of the shape of the curve. Every time there is an update to the curve you'll must exhume the ratio and perform a linear interpolation using the ratio and bounding knot U coordinates as input to compute the U coordinate of the deformer: U = ( ( r * u2 ) + ( (1 - r) * u1 ) ); The U coordinate can then be used to lookup the position coordinate and place the deformer on the curve. The trick will be getting the proper knot indices and U coordinates as they will differ between linear and cubic curves, as well as open vs. closed curves. ICE won't give you access to the details you need to pull this off for the general case, but you can definitely do it without much trouble in a scripted or C++ operator. I have a prototype up and running in ICE (assuming an open cubic NURBS Curve), but the 'UV to Location' node is broken as the output position is offset by a fixed amount from where it's supposed to be. It's also very finicky about the construction history of the curve. Any manipulation of the control points or curve geometry results in flakey output. I advise using a scripted or C++ operator for this particular problem. Matt ------------------ Matt Lind Animator / Technical Director Softimage certified Instructor matt.lind(at)mantom.net Date: Tue, 12 Apr 2016 22:18:53 +0100 From: pedro santos <probi...@gmail.com> Subject: Distribute between knots? Know the percentage position of a knot? To: Softimage Mailing List <softimage@listproc.autodesk.com> Hi How can I distribute deformers along a curve not by the total curve percentage, but in between-knot percentage? This because when I stretch a part of the curve I don't want all the deformers to be re-distributed, but only the ones where where the curve length between their bounding knots have changed. An using Curve Constrain uses the whole curve lenght. Null constrained at 20% on a curve. Below the duplicate of the setup but the curve was deform in such what the null even passed the knot. [image: Inline image 3] In Green is the ICE attribute "PointU" which I thought it would give me somethig I could work with but no... No matter how I deform the curve that PointU is always the same. And apparently there's no KnotU. If there were I guess I could work out something with the bounding knots :/ [image: Inline image 4] Basically I want to keep working with approximated curves, since it will be used for deformation afterwards and splines aren't as smooth, but I see no what to solve things in each section of the curve. Let me know if there's a way I at least can Access the Knots' U or Position :/ Thanks! Pedro ------ Softimage Mailing List. To unsubscribe, send a mail to softimage-requ...@listproc.autodesk.com with "unsubscribe" in the subject, and reply to confirm.