[Sidefx-houdini-list] Converting FK to IK?
rsutton at dnahelix.com
Wed Mar 22 12:22:38 EST 2006
Peter Bowmar wrote:
> I'm kind of sick right now and my normally slow brain is moving
>backwards it seems... I have some mocap data in IK (from Biovision)
>that works OK (mildly broken but I can fix it with a script). However,
>mcbiovision isn't bringing in the feet and hand "leaf" nodes so I
>don't have hands :(
Ah diddums ;)
This perl script will add a redundant bone to the end of each skeleton
branch since the houdini conversion script mcbiovision drops the last
bone in any branch. You get your fingers, toes and heads back!
$ bvhpad.pl orignal.bvh > padded.bvh
$ mcbiovision padded.bvh
My perl is so rusty the engine has fallen out, so caveat emptor. Most
especially if your motion data lines have a leading space it screws up
horribly. Someone fix that.. please?
> However, mcacclaim is correctly bringing in the feet and leaf
>nodes, but has a lot of bone flipping problems so I can't use it
You can fix a lot of stuff simply piping these channels through a
transform chop. Make sure you get the rotation order correct though..
>Also, bizarrely, the scale is off. What I've done that seems
>to work is take the FK Acclaim feet and hand objects and graft them
>onto the IK from Biovision to create a complete character. All fairly
>easily scripted so far.
> What I can't get my little brain around is converting the FK
>hands and feet (mostly the hands) to IK so I'm not mixing editing
>solutions when it comes time to edit this frankenstein monster. IK has
>a lot of advantages over FK for mocap editing, I've found recently :)
> So, anyone have any ideas? I was thinking I could put a null as
>the child of the FK bone, then use a Geometry CHOP to capture its
>world position space, then I'd have an affector and then convert the
>bone to IK. Does that make sense though? I could script that pretty
>easily too I'd think...
You pretty much have it but I think your making life hard on yourself.
Parent a null to your FK creatures bone and that's your IK end affector.
You probably want to parent another null to the previous bone to create
a twist affector, or maybe keyframe this otherwise you might find
yourself recreating the flipping ;)
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