Procedural - Arnold for Houdini

You can export any object as a .ass file. A procedural (also called stand-in, proxy or placeholder) references the .ass file on disk (or other procedural formats supported by Arnold such as .obj or .ply). They allow you to keep your working scene light and workable by deferring the loading of geometry data until render time.

HtoA dynamically adds object (OBJ) nodes for all procedurals loaded at startup. For example, with the default HtoA installation, you get the Arnold Alembic, Arnold Usd, Arnold Procedural, and Arnold Mandelbulb object nodes.

Arnold Procedurals can be created by tab-typing Arnold Procedural or Tab > Arnold > Arnold Procedural at the OBJ level. The procedural node can be used to load an external geometry file or a compiled DSO (Dynamic Shared Object).

Arnold Procedural

The following parameter are Arnold procedural specific parameters.

Target SOP

Use an object in the scene to attach as a bounding box preview.

Proxy SOP

Provides a bounding box representation for visualizing the contents of a procedural when importing geometry into Houdini using a SOP.

Operator Graph

You can choose to connect any existing operator graph to a procedural.

To connect a Procedural Operator to an Arnold Procedural, you have to pick the operator ROP in the Arnold properties of the arnold_procedural OBJ node. Use the Arnold Properties top-level Arnold | Operator Graph parameter to pick the operator ROP, which can be anywhere in your scene.

_{Procedural Operator parameter in Arnold properties of Arnold Procedural}