I'm currently having a problem where loading an fbx rig as a Target Character for export is not showing all the bones in my rig.

I'm using Houdini's default Mocap Biped 3 Character:

Then I export that to an FBX format.
Here's the FBX File:
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But when I load it up in the Mocap Studio via the Export panel's Target Character dropdown, I get this:


There are missing bones (particularly the legs), the rig network looks like this:

In addition, if you import the FBX file back to Houdini, the bones are complete:


So, Houdini is able to export FBX rigs no problem.
Are there certain requirements in iPi for Taget Character FBX rigs?

I found a related thread, but it does not solve my problem.

Hi
Thanks for reporting. Indeed, Mocap Studio has troubles with this rig.
The legs are missing because importer detects a character's root bone incorrectly. We have a fix for this already.
However, there is another issue with this character resulting in wrong orientation of the left arm. We are working on this now.

Thank you for the response, I ended up doing a bit of a workaround for now.

I converted the bvh exported from the Motion Capture using a Houdini command to just be joints.
Then in Houdini, I created a bone rig that matches the mocapbiped of Houdini, essentially re-creating the bone hierarchy all with look-at constraints based on the joints. It just needed manual tweaking to get the bone axis rotations correctly. The resulting transfer is not entirely perfect, but so far looks workable.

Looking forward for the update, it would be great if iPi soft would support a Houdini mocapbiped rig. This would open up creating more motion clips for use with Houdini's crowd system.

The model - mocapbiped3.zip - looks somewhat unusual.
The root ("MASTER") and Hips are exported to FBX as locators rather then joints.
The rest of the skeleton joints are exported as hidden.
The LeftShoulder_To_LeftArm joint has "-1" scale (all other joints have positive unit scale).

iPi Mocap Studio, just like most of the software packages in 3D industry, expects FBX models to have normal joints for joints (not locators, not hidden joints), and positive scale for all joints.

I think you should be able to fix all these issues inside Houdini. There should be relevant settings somewhere in FBX export options, or in Houdini node properties. Just set them before exporting model for motion transfer in iPi Mocap. You can revert back to old settings after you import mocap file.

Thank you for looking into it. I did notice the negative scaling of the leftarm while I was doing my retargetting rig, quite unusual.
I'll try and raise this issue over at SideFX.

Cheers!

Hi again, I looked into exporting the mocapbiped3 as an FBX in ASCII format.
After checking the generated file, I found these lines of code to be the closest on the would seem to set the visibility.

If so.. every joint really is being set to invisible.

I'm curious why iPi Mocap can see some of it, and not the others?
For example, in the screenshot on my first post, the dropdown can show the RightShoulder_To_RightArm on the list.
Then, looking into the FBX ASCII for the same joint:

It looks like the visibility is set to 0, yet it can show up on the list.
Lastly, comparing it to a joint that is not visible on the iPi Mocap list:

They seem to have the same visibility settings, yet it is not being shown in the list?

Would you happen to know if a different part of the ASCII is responsible for the visibility?
I wanted to check and confirm why parts of the rig is not visible in iPi Mocap. Because when I load the FBX on both Houdini and 3dsmax, they both show the complete joints.

I've attached the ASCII file exported from Houdini below.

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Maybe this video tutorial could help, you would just have to convert as if were using iPi BVH export using the default iPi skeleton.

Worth a look if it would help.

Houdini Install BVH Into Mocap: https://www.youtube.com/watch?v=IPupRqb58FE

I am not familiar with the workings of Houdini, but I would think you could rename all the bones in houdini to match the iPi or Mobu naming convention first and save it as a new biped character in Houdini to use as your base skeleton/character for importing into iPi as the target character for previewing animations?

Possibly on export as FBX from iPi it would just be able to be imported to Houdini as an FBX with all animations from the take like any other 3D package would?

Not sure, just a thought, but without that it seems like a process to get external animations linked to the Biped1 in Houdini.

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I see changing the bone naming doesn't solve anything, the Hips are not displayed as a bone, you're correct, so it will never export as a complete attached fbx skeleton from any 3D package, looks like they use a right/left hip config. with the Hips as a null, so somehow in the above CMU BVH conversion, they get it to work, but I don't think direct import into iPi will ever work, please post again if you can get it to work directly.

I see the free version of Houdini doesn't offer exporting of fbx files, but the paid versions do, educational allows exporting with watermark.

I see the OP is running a paid version, as they exported the Biped1, but thought I would post this for anyone else wanting to check out Houdini.

Houdini 16.5 looks really good with a few new features and at $199 a yr. for the Indie version, and free Houdini engine for exporting to other 3D packages, no watermark.

Link to Indie version description: https://sidefx.com/products/houdini-indie/

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I am wondering if you could load the Biped1 into Houdini, then from it's T pose delete all the original bones and using auto-rig to create another bone structure and bind it to the Biped1 mesh, would be the same as doing it to any other character mesh I guess?

It looks in the videos I watched that it creates a skeleton structure that can be adjusted better to a common skeleton, with an actual Hip bone?

Just a thought, I am not able to go through all the steps needed to do it, but possibly an option, if it would work.

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