You may wonder: why can’t I use kick -set options.shader_searchpath to tell Arnold where to find shaders?

Well, it’s because kick loads the ASS file first, then applies the kick -set parameter overrides. And also, Arnold when loads an ASS file, Arnold automatically loads shaders from the shader_searchpath as soon as Arnold loads the options node.

Here’s the sequence of events:

1. kick loads all plugins specified by -l or by ARNOLD_PLUGIN_PATH before it loads the ASS file
2. kick loads the ASS file. When Arnold loads the options node, Arnold automatically loads all plugins specified by options.shader_searchpath.That’s why the options node is at the top of an ASS file: so Arnold can load any required shaders before loading the shader nodes. It you move the options to bottom of the ASS file, the shader nodes in the ASS file won’t be loaded.
3. Finally, after all the nodes are loaded, the -set parameter overrides are applied. At this point, it’s too late for any shaders from the -set options.shader_searchpath loacation. The corresponding nodes were already discarded during the loading of the ASS file.