User Guide > Quickstart > Exploring Digital Assets 

Creating a Simple Digital Asset

Digital assets are an important part of working in Houdini. Now a Technical Director can easily package up a series of complex Houdini networks into a single asset that provides portability, usability and significant productivity gains. These assets play well with any pipeline and are very accessible for artists and animators, even those with a limited working knowledge of Houdini.

For those of you who haven’t used digital assets the best place to start would be to create one from scratch.

The following lesson file contains a modeling network showing some polygon operations that result in a subdivision surface model. One half of the model was created to take advantage of symmetry then a mirror operation and a subdivide operation are applied to preview the results.


Part One: Create a Digital Asset

 


1. Create a simple Network

Select the beatrice object and press i to go into it. Here you will find a model of half of a character's head. Press tab > mirror, press a to select the whole model, and RMB-click to accept. Next press tab > subdivide, press a to select the whole model, and RMB-click to accept.

Mirroring and subdividing a model in this way is a repetitive task that is perfect candidate for building a custom tool using the digital asset methadology.


2. Create a Subnet

In the Network pane, select the mirror and subdivide operators and select Ctrl-RMB > Collapse into subnet. Rename this new tile mirror_subdivide.

All the parts of a digital asset need to be contained within a subnet in order to make them portable. It is important that the asset be portable so that it can be re-used and shared with other modelers.


3. Create a Digital Asset

Select RMB > Create Type From…. Name the asset mirror_subdivide and Mirror Subdivide. Name the OTL Opmodel.otl. Click Accept. It is very important for you to use these names because you will later update this digital asset with an updated file.

Click on the varkous tabs. Settle on the Parmameter tab.
The next step is to convert the subnet into an operator type.
At this point you name the operator type then store it in an operator type library, – which is where the term otl comes from.
Lets call this asset, "mirror subdivide" and store it in the "Opmodel" OTL.
Otls make it possible to manage and distribute digital assets into your pipeline.
They can be stored locally to enhance your personal work or put into general distribution to benefit everyone at your facility.

After the library has been chosen, you are presented with the Operator Type Properties panel which lets you define a high-level interface using a combination of channel references, scripts and expressions. These are the controls that will be made available to the artists who use this tool.


4. Create a custom parameter

Select the mirror_subdivide subnet then press i then drag depth parameter to parameter panel.
Press Accept then show the depth control in the Parameter pane.
Press tab and create a new mirror_subdivide next to the other. Delete it before moving on.
For example we can dive down into the subnet and drag the subdivide sop’s "depth" parameter to the type properties pane.
When we press accept, the asset is stored and its controls are available in the mirror/subdivide’s Parameter pane.
If we press the tab key then we find that the custom mirror subdivide sop is available and can be used for other models and by other modelers.


Part Two: Update the Digital Asset

 


1. Install a new OTL

Install the OPmodeling.otl library then open the OTL manager panel.
Click on the new library to make it the current definition.
When the digital asset was created and stored in the otl, it was set up as a reference.
The new tool references the operator type definition found in the OTL.
If this definition is updated, then the new definition can be used in its place.
Let’s imagine that we want to take advantage of some new controls added to the mirror subdivide asset by another TD.
By loading in a new OTL which also contains this tool then by selecting it in the operator type library manager we can choose this as the current definition of the tool.


2. Remove the old definition

MMB on the operator.
RMB > Synchronize.
Show new controls in the parameter pane.
Click on button to show its affect.
At first nothing happens. Houdini will protect your scene so that new definitions don’t alter your work until you approve.
If we middle-mouse button over the asset then we see that it is not yet synchronized with the new definition.
We can choose to match the definition from the operator’s pop-up menu.
The asset is updated and includes all of the functionality of the original plus some extra controls built in.
When an asset is updated it can new controls, geometry, kinematics, shaders or anything else.
For instance, you can press the setup button to template the end of the chain, shade the templated geometry then show the original model as a wireframe cage.
This sets up a modeling cage similar to hyper-nurbs style workflows found in other popular modeling applications.


3. Apply the tool to another model

Zoom out. Toggle on the display of the body in the network pane. footprint the face.
Tab > Mirror/Subdivide – pick body to get results.
Click display on merge sop for exporting.
Now lets use this tool on another piece of geometry. As the tool is activated from the tab key, you can see a prompt for selecting the geometry.
The asset has been designed to display this prompt in the same way as any other Houdini tool. This ensures that new digital asset tool are easily accessible to other Houdini artists.


Part Three: Turntable Digital Asset

This new functionality was easily introduced into the modeler’s workflow using the strong referencing capabilities inherent in digital assets. As a digital asset like this gets shared around a studio, significant productivity gains will result.

Of course this asset only contains a couple of nodes with a few controls. Lets take a look at a more complex example.Imagine the number of steps that would be needed to take this model and prepare a turntable animation for daily review.


1. Create a turntable

Go up to object level. Press tab and choose turntable.
Select the model then RMB to accept.
Switch to the ??? camera.
Click on the turntable’s help button. Scroll down to show informaton.
Playback the animation to show the turntable.
This is another perfect place for digital assets to come into play.
Lets go back up to the object level and from the tab menu, access a turntable tool which is part of the OPmodeling OTL we loaded a few steps ago.
OTLs can contain many assets to provide a sort of toolset for building up a workflow.
Once it is place, switch to the turntable camera and use the built-in HUD sliders to position the model within the dome.
If you don’t know what the various controls do, you can open the embedded browser and query the turntable tool to read the asset’s help.
This built-in help makes it easy to share assets across the pipeline.
Press play to preview the results.
Now modelers throughout a studio can quickly setup their work for review without worrying about cameras and lights and setting keyframes.