Autorig Tools

Using the autorigs is an alternative to rigging your own character.

Ready-made auto rigs

There are two ready-made auto rigs on the Auto Rigs shelf. All you have to do is click the Biped Auto Rig or the Quadruped Auto Rig tool on the shelf and you are ready to animate.

There is also a Toon Character on the Auto Rigs shelf, which is animation-ready. It also comes with built-in deformation, facial shapes, and squash and stretch ability.

Build your own rig

Houdini gives you the option of creating your own rigged character by connecting body parts together. There are several appendages for both the biped and quadruped characters.

Simply create a character placer in the scene, and then add other body parts using the tools on the shelf. The following are some of the appendages you can use to build your own rig:

Note

There is also a tool called Reconnect Part on the Auto Rigs shelf that is useful if you ever select the wrong hook object or change your mind about where you want the body party to be connected.

Once you assemble your rig, you can select all of the body parts you want to make into a rig (including the character placer), and click the Create Rig tool on the Auto Rigs shelf.

Motion capture

The best way to bring a mocap into Houdini is to create it in a application that is compatible with FBX. This will allow you to import the animated skeleton with mocap baked in, as well as the skin. This will save you the trouble of rebinding the skin to the rig.

Another way to do this is to make your file a BioVision file, and run it through the Houdini Command Line Tools. This will create your .cmd and .bclip files. For more information on stand-alone utility motion capture formats see: mcbiovision, mcacclaim, and mcmotanal.

You can then import your .cmd file by selecting Run Script from the File menu or by using the Hscript Textport window.

If you don’t see your skeleton fully assembled and moving, check the file path in the CHOP is correct. If your current $HIP is not the same directory as your .cmd and .bclip files, you will have to update the path to point to the proper directory and file.

Tip

You can collapse nodes into a subnet by selecting the skeletal structure and pressing ⇧ Shift + C .

Once the .cmd file is imported you can import geometry and bind it to the animation manually using the tools on the Character tab of the shelf. For best initial results, it helps if your character and mocap skeletons are similar proportionally.

Example: Binding motion capture to the toon character

  1. Create a toon character by clicking the Toon Character button on the Auto Rigs tab of the shelf.

  2. Once the file is imported, collapse nodes into a subnet by selecting the skeletal structure and pressing ⇧ Shift + C .

  3. Change the Uniform Scale parameter on the newly created subnet object node to the appropriate scale. Matching up the COG position

in the Y axis is the best way.

  1. On the Animation Data tab of the Toon Character object, click the Generate Mocap Rig button, select any bone on the skeleton, and press Enter .

  2. Interactively map the parts to the skeletal structure in the viewport. You can map multiple parts of the rig to the same bone using the Pick button, and optionally save the settings for reuse on similar named skeletons.

    Note

    In some cases not all bones are used. For example, the legs use Inverse Kinematics (IK), so you do not need to select the lower leg bone. Select the upper leg for the Thigh control, and then the foot bone for the Ankle control.

The toon character will follow the skeleton. If it is slow, increase the sample rate on the mocap rig to the same rate as your animation.

Tip

If the character appears to be floating off the ground, modify the root scale offset.

The animation is done using chop() expressions. The toon character’s spine and arms reference the File CHOP that is reading all of the animation data. To convert to keyframes on the mocap rig, click Save and Apply Keyframes. This converts all the CHOP channels to raw keyframes and applies them to the toon rig. Houdini will smooth out and reduce the number of keys. This is controlled by the Refit Tolerance, which writes out all the key data and can take a couple of minutes depending on the amount of channels and the length of the animation. Reading the data back in and refitting is much faster. Once this process is complete you can tweak the animation manually.

You can click Apply Animation on the mocap rig to reapply CHOPs expressions to your animation rig. When you use CHOPs expressions, it is easy to change the source animation by changing the .bclip file to another with the same skeletal structure.

Note

There are also parameters on the animation rig that allow you to save/load the raw keyframes.