Hi everyone,

I've gotten motion capture data into Houdini using mcbiovision. It created a stick figure that appears to be working using rotations and parenting.
I have a character rigged with Inverse Kinimatics. How do I bind the motion capture data to my character? It seems that there should be some way to do this, or else motion capture in houdini is useless for kinematic character setups. Has anyone been able to accomplish this?

Thanks,
Christine Smith
Northrop Grumman
Engineering Visualization Resource

You can use either:

mcbiovision -f (forward kin)
or
mcbiovision -i (inverse kin)

This will create the bone hiearchy found in the biovision file. You'll need to apply this bone hiearchy to your character, as your rigged character will likely not match.

Using the FK method is recommended, as the generated CHOPs drive the animation anyway, and you'll get the exact replication of the animation without the IK solver overhead.

Alternatively, you could try to massage the FK data to fit your bones (a matter of changing which bones the channels export to, and fiddling with the channels in CHOPs). Depending on how different your setup is from the generated character, this might be easier than re-capturing your character using the generated skeleton.

Hi twod:

>You'll need to apply this bone hiearchy to your character, as your rigged character will likely not match.

I tried -f and -i and they result in a very freakish character. Only -w alone gives me a proper character. But there are no bones as with -f. Only objects with rotations and translations. My character needs to be smoothly deformed, so he definitely can't be set up in a bunch of different objects.

I'm still unsure of what to do. Let's say I went ahead with the freakish character setup. Do I then re-rig my character so that it has the exact number of bones and parents as with -f, move the bones around so that they look like a real skeleton, then bind the bones to my character using capture regions?

Thanks for your reply!!
Christine

Hi Christine,

What version of Houdini are you using? I suspect that in your particular Houdini version you need to append the “boneconvert” command to the generated .cmd file.

You will also need to run the “kinconvert” command after “boneconvert” in the textport.

The two textport commands are necessary as there has been many changes to bones and kinematics since the mocap tools were built.

Hi,

I'm using Houdini 6.5.102. boneconvert gives me messages saying that it only partially converted the bones. The character still looks the same (freakish) when its done. kinconvert locks up houdini for hours. Using the -w option alone, the character looks good and moves properly but has no bones for boneconvert or kinconvert.

Thanks guys!
Christine

If you have objects moving around correctly but no bones, you can as a last resort manually ( or scriptedly…) add capture region sops to each object and then use these to capture and deform your geometry. Or parent individual bones to each object and use those instead.

Thanks, I just might have to do that.