User Guide > Quickstart > Exploring Digital Assets 

Working with Digital Asset Characters

Digital assets play an important role in the creation and animatin of CG characters in Houdini. Digital assets be used to create animator-friendly interfaces for characters while also providing support for a flexible production pipeline. Digital assets can also be used to streamline various rigging tasks.

The goal is to make a character that can be easily updated while utilizing a user interface that enhances the animator’s ability to get their work done.


Part One: Rigging the Leg

Let’s begin by rigging up the foot. We will need kinematics running from the hip to the ankle and a reverse foot setup to give us proper heel-to-toe rolling.

Since this kind of foot setup is typical of most biped characters, a foot-control digital asset has been created and made available for use with this character.

1. Set up a Top view

Tumble and zoom around. End up focused on the feet.Turn off the model’s display to let us focus.

2. Add and Position a Foot control

Press tab > foot control. RMB-click to put it at the origin. Press tab > Transform.

3. Edit the Position of the Nulls

Go to the Setup tab and turn on make nulls editable. This will make the nulls selectable on an individual basis

Snap nulls to bones.

Scale up foot icon. Toggle off "editable" flag.

Here we get a foot control asset and place it into the workspace.

It gets moved into place and the first thing we notice is that the control nulls are not located where they are needed.
Controls have been added to allow for these points to be customized for any foot which allows this setup asset to work with any biped character. In only a few steps the nulls are aligned with this character.

3. Add Kinematics

Go to the kinematics panel. Click add kinematics.

Next we will hook up the kinematics for the leg and foot using a button that runs a series of hscript commands to hook up the null objects of the foot control to the leg bones.
Notice how when the button is pressed, the various bones are referenced. Digital assets can contain scripts for simplifying tasks that would otherwise require a lot of clicks.
Now lets test this.

4. Test the setup

Access the pose tool. Click on the foot control and manipulate it. Undo.
When we pick the control with the pose tool a handle and various HUD sliders appear.
These are the animator’s controls.
As you can see the foot controls built in interface along with the quick rigging and kinematic setup make it easy to get a foot roll with Houdini.\
You can even mirror the whole left leg along with the control object to get a new leg with the foot_control already setup.
Very quickly you can see the power of using digital assets as a rigging tool for setting up characters quickly with easy to use handles.
A similar technique would be used to rig up other parts of the character.

4. Mirror the arms and legs

5. Create the character asset

Zoom out in network to see all the parts.
Select them and collpase into subnet.
Drag the foot control to type manager panel. Show parameters.
Characters themselvs are best set up as digital assets.
This involves taking all the bones, geometry and shaders and collapsing them into a subnet.
This can then be turned into an operator type with its own controls.
To help build up its interface, we can simply drag nodes such as the foot control node into the properties panel and the parameters are published. From here the character’s interface is built.
Let’s jump to a version of this character that is all rigged up.

Part Two: Posing a Digital Asset Character


Install the OPsiggraph.otl library.

1. Load the Character

Press tab > Beatrice. RMB click to accept and place girl.

Zoom and Tumble to view character.

Show parameter pane. Play with the display options under appearance. Turn off the "other bones."

2. Position the Character

3. Pose the Character

Get the Pose tool. Click on the feet. The whole character is selected.
Turn off selectability of digital asset node and turn off "select entire subnet."
Click on feet. Now the foot controls appear with rolling sliders and main handle. Pose the foot.
Pose the other foot and the pelvis control.
Pose the hands. (handles) (there are not any finger or facial controls)
Pose the spine (bones)

4. Add a Second Beatrice

5. Update the Digital Asset

Install the Opsiggraph_new.otl library.
Select the new defintion.
Update Beatrice.

6. Set the Display options

7. Continue Posing the Characters