An 'Introduction to Procedurals' tutorial can be found here.
Before you can use procedurals, you will have to first export some geometry to be used later.
To export the geometry you must:
Export .ass file from Render Setup: Arnold -> Archive
You can also export a .ass file by going to File->Export->ASS.
The archive is saved as an Arnold Scene Source (.ASS) file. You may export single objects as well as a whole hierarchy made out of multiple objects. You can also export single or a sequence of frames. In this situation, the frame padding value from the 3ds Max Render Setup will be used in the names of the ass files.
During export, Arnold's current render settings will be used. Therefore, you should finalize these settings before exporting the procedural. For example, you should choose whether you wish to export with motion blur enabled or not.
To open the .ass file, you will first need to create an Arnold Procedural primitive.
Create an Arnold procedural here
Note that in addition to archive (.ass) files, pre-compiled custom procedural programs in the form of a dynamic library can also be loaded at this point, though none are shipped with MAXtoA currently.
3ds Max maps cannot be exported to an Arnold Scene Source file, and will not render outside of MAXtoA.
Load .ass file as procedural
This will create a procedural node that you can use in place of regular geometry. The parameters of the procedural node are described below.
Procedurals are supported via the Arnold procedural node. This node has the following parameters:
Arnold procedural parameters
The path to the archive (.ass) file.
Sequences are automatically recognized if they use four-digit padding for the frame number (for example name1001.ass, name1002.ass, ...).
In the case of a sequence, the Animation Support group can be used to define the sequence range and some playback options.
This custom namespace can be used instead of the procedural name, to reference contents through absolute or relative paths.
The Up Axis for the procedural. Z is the default.
Enable reading a sequence of files.
The start frame of the .ass file sequence.
The end frame of the .ass file sequence.
The timeline's frame at which the .ass sequence starts to be used.
The timeline's frame at which the .ass sequence ends to be used.
Sets the playback speed of the procedural's animation.
When on, if the animation range exceeds the sequence range, the sequence is looped.
If on, the first and last .ass file of the sequence is used before and after the Animation start and end frame respectively. Else, for those frames, nothing gets rendered.
When on, if the animation range exceeds the sequence range, the sequence is read forward, then in reverse, then forward again and so on.