Hi all,

I was following this learning video (https://www.sidefx.com/tutorials/rigging-series-03-left-arm/?collection=45) and in minute 31m40s I try to replicate the same steps and get suck into a strange behavior.

First create the two bones chain. Then create two controllers to move the respective bone. Create a “Blend Constraint” for each bone to get the FK working. And it does. Works like a charm.

When I create a “IK With Twist Affector” and “Add Kinematics” to that same bone chain, the IK doesn't work because the blend constraints that I got for the FK, as expected.

The idea, like said in the video, is to create inside the constraint a “Blend Constraint” node to use as a switch and get the world space or world space with offset (IK or FK action). My problem is that when I create the “Blend Constraint” node I still cannot move the IK and I lose the FK as well. The'res anyone who got the same problem? I've check the video numerous times to see if I miss anything but I can't figure it out.

Thank you for your help

there was an issue with constraints that was fixed just before the holidays - try upgrading to the latest daily build Houdini 17.0.451

Thank you, Michael Goldfarb. I will try to upgrade Houdini and try again.

goldfarb
there was an issue with constraints that was fixed just before the holidays - try upgrading to the latest daily build Houdini 17.0.451

Goldfarb,

Just for your interest, I have tried with the new daily build (17.0.452) and works only if I create the IK first and then the FK constraints. Other strange behavior that I find out is if I create the FK constraints first and then the IK, delete all nodes and then make Undo, everything works fine. Strange but true

Thanks again for your help and congrats for the great tutorials.

My 2 cents:

Again, mr. Goldfarb thanks for amazing tutorial. And - Icatalo - thanks for a Magic Fix. I'm on 17.5.286 (Daily Build) and had exactly same problem. And deleting all nodes from L_Shoulder_root down and Undo just make it all work. A bit worrying, TBH.
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I just opened older backup file, to redo this and make a proof video, but looks like once it starts working, it works. So even for me looks like users fault .
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On the very end of arm setup you went back to this blends, and mention that we should make 2 blends instead of 1. Maybe it will works from the beginning if this was set correctly. I made notes to myself watching this, so I'll check this next time.

I also was stuck on this for a while (Using 17.5.327) and began to doubt if I messed up something earlier. Thanks for the solutions!

I'm working on the left leg part of this outstanding tutorial. Despite the discussions and tips in this thread here, I keep on running into small problems when entering the FK/IK blend parameter into the constraints. If I enter them in the ‘simpleblend’ node (like Michael shows in the video), I get a small unexpected and undesired rotation of the leg root in Z (this also happens if I manually change the blend parameter of the ‘simpleblend’ from 1 to 0). I therefore tried to enter them into the blend of the ‘offset’ node of the constraint and that seems to work fine.

@Michael Goldfarb: is this a valid way of working? After all, it is the offset node that blends the 2 worlds, or not?

Piet

P.S.: I posted the same comments in Vimeo, but I think such discussions belong in here…

I'll have to go back and work through that part again to see if anything has changed since the videos were made
but if you get something that works then you're good

there have been updates to the constraints in since the videos were made so I'd make sure you're using the latest Production Build.

I ended up building a similar setup as you showed for the arm, so with an additional constraintblend node within the constraint. That worked out perfectly well, no strange rotations anymore when changing from FK to IK and back.

Thanks for the feedback.