Hi JP, Yes, I have seen this happen a few times before.
All I can say from my experience is that when you're scrubbing the timeline, the IK RP solver does not do a full calculation, similarly if you did a dynamics solve and scrub the timeline without maya doing an initial iteration for each frame. From my understanding the rotate plane is just a way to get out of the gimbal lock with the IK algorithm (Im guessing, it is because the solver uses euler angles in its maths) Id bet it would be extremely difficult to get a hold on Mayas IKRP solver algorithm. There are a few studios out there that uses their own in-house IK solver plug-in to workaround Maya's. But yeah, if anyone could share some light into this, that would be awesome -Jeremy On 30 October 2010 11:51, Beau Garcia <[email protected]> wrote: > Hey JP, > > Sounds like a strange one. Have you had any "Warning: Cycle on <node name> > may not evaluate as expected" warnings ? . I have seen similar strangeness > when a cycle in the dependency graph is present, causing unexpected > evaluations. > > The warnings might be suppressed with " cycleCheck -e off " . > > You can access ik solver algorithms on the net, i don't know where to find > the exact one that Maya uses though. > > Cheers, > Beau > > > > > > > > On Fri, Oct 29, 2010 at 4:34 PM, JP <[email protected]> wrote: > >> Hey guys, >> >> So this isn't strictly a Python question (err..not at all) , but >> there are a lot of bright minds here and I hoped someone might have >> some experience with this since the rigging and python worlds often >> overlap. >> >> I'm having an issue where an ik RP solver on a leg will sort of >> 'freeze up' when the ik handle and the character hit a certain pose. >> For instance, everything will work fine when you scrubbed up to frame >> 50, and then the knee joint would 'lock' to whatever the preferred >> angle was set at (i.e., <<0,30,0>>). The kicker is that you could >> then scrub *backwards* and the solver would still be locked. If you >> changed any other inputs to the joints being solved, like the scale >> for a stretchy leg, the solver would seem to 'pop' back to solving >> correctly. >> >> When rigged, the joints are oriented to a plane, the handle is >> connected while the joints are bent, the pole vector is placed along >> this plane, and a preferred angle on the joints is set...so I think >> I've got my bases covered there. >> >> So IMO, there's some black magic happening in the ik solver >> computation that I don't understand. Another oddity is that setting >> the preferred angle for the joints at, say, 30 degrees wouldn't fix >> the problem, but setting it at 90 degrees would (at least for now, but >> who knows when this will rear its head again?). My guess from the >> scrubbing issue is that the node doesn't do a full computation unless >> certain input plugs change. It's hard to say, because an ik handle is >> one of those nodes that (for some reason) doesn't actually have >> connections to what it's changing. >> >> I would LOVE to get my hands on the algorithm that's used to compute >> and set the joint rotation values. Any Autodesk people in the >> house ? :) >> >> Thanks all, >> JP! >> >> -- >> http://groups.google.com/group/python_inside_maya > > > -- > http://groups.google.com/group/python_inside_maya > -- http://groups.google.com/group/python_inside_maya
