local rotation axis

[TheUsualAlex]

Does one has to worry about local rotation axis in Houdini as it is in Maya?

[edward]

What problems are you worried about?

In general, it's good to pay attention to the orientation of the bones and your controllers so that they animate with sensible numbers.

[thekenny]

Are you asking about how maya flips the axis for bones in a chain?

Houdini doesn't have that "feature"

-k

[old school]

Or is it gimbal lock you are referring to?

If so, then yes you have to be careful when ordering your rotations. You can always use the TRS R? rotation order options in the object parms if you can anticipate how the animator will do his keyframing but gimbal lock is inevitable if you key all the r[xyz] channels in the same object. I think the TRS R? ordering in the node is unique to Houdini. Is it?

Best to bust the Rotations apart in to separate nulls in the heirarchy to handle that situation. At least pull the main rotation channel out then handle the other rotations in a second child null.

Houdini6 has a nice addition with the qlinear() function for rotations. It uses quaternions to drive the rotations between keys. Better behaved but if you are used to animating with standard cubic() or linear() rotation segments, they will take a bit getting used to. I found they tend to rotate more abruptly around the keys.

You need keyframes for all three r[xyz] channels at the same time or else things get real screwed up. No GUI to "lock" the keys together when editing so be careful. There are dotted linear lines between the keys as quaternion rotation channels have discontinuities all over the place. Ever seen quaternion rotation channels in CHOPs from mocap solvers? You will see why there are dotted lines between the keys! Note that the transform CHOP clears up those discontinuities fyi.