There are two types of procedurals:
For ASS files, you use an Arnold Procedural node.
For a compiled procedural plugin like Mandelbulb, you need to create a Geo object as a placeholder in your Houdini scene, and tell HtoA to translate that Geo object into a Mandelbulb node. Don't worry, it's not as a hard as it sounds.
Let's get started...
Download the start scene and open it in Houdini. The scene contains a Point Light and a Camera.
Creating the Mandelbulb Node
Select the geo node and click on the gear icon and choose Edit Parameter Interface...
Add a new Folder
Drag Folder from the Create Parameters list over to the root above the Render folder and name it Mandelbulb
Add the mandelbulb parameters
To add parameters, click the By Type tab on the left side. Select the type of parameter you want to add, then drag it into the Existing Parameters pane, or click the “move right” button.
Use the options under Parameter Description on the right side of the window to customize the parameter's Name and Label. HtoA detects user parameters that start with ar_ and uses them to translate to the parameters of the procedural in Arnold.
Assign the material /shop/arnold_vopnet1 in the Render tab of the mandlebulb node
Now look through cam1 and render the scene using your preferred context. The procedural will calculate the mandelbulb and render the following image.
With the procedural working you can now create a reusable asset,
First right click on the geo node and choose Create Digital Asset ...
A dialog will pop up asking what you want the asset to be called.
After this you may be presented with another dialog for you to confirm the parameters and remove any "spare" ones, it should be safe to allow the spare parameters to be removed. Once this is all done you should see your new Asset available in the Digital Assets menu.
The next part of this tutorial discusses the Mandelbulb parameters and the effects of changing them.