refracting aovs in karma

 make a custom attribute, i've called it poso2, i'm hijacking the Position value for this & fitting it between 0 and 1.

in karma, use the geompropvalue to load it in to the shader. here i use a mtlxdot because apparently it doesn't change the value of the attribute (?).  i plug it into a karma aov thing and name it "poso", using the $OS. Here i'm using the float value to drive a colour ramp.

In the render settings, aov section, scroll down to "extra render vars" and add one. put in your name - "poso" in our case. set format to color3h and data type to color3f.
The source name is :
C<TG>.*L
and Source Type is LPE.

I actually used the settings created when you select Glossy Transmission for this, then changed the name to Poso. Seems to work though!

Karma per light aov

per light AOV stuff with Karma.

In your light, in the Karma tab, add a name to the LPE Tag. Here I've typed "A".

On the right hand side of all the AOV bits, you can tick Split per LPE Tag - ON EVERYTHING

crowds in solaris/karma

 Bring in crowd from obj using SOP Crowd Import node (here it's still packed agents). Create Instanced SkelRoots is preferred I think

Stylesheets don't work with Karma/Solaris (as far as I know!) To target props/shapes in a crowd you're best off using Collections. Here we're making collections of the hammer prop. 

It's important to tick Allow Instance Proxies in Collection!

The syntax is %reference:/path
In the example it's %reference:/crowd/agentdefinitions/ball/shapelibrary/l_hammer

Here's the stage scene outliner thing

Assign the materials to the collection by typing in the name. Eg. %hammer

Be sure to expand the Material Binding and tick Include Descendant Primitives in Collection
You might have to change the Strength to Stronger or Weaker than Descendants too.

I couldn't see a good way to access point attributes (eg. per agent float/int values) but Material X does read them - so I guess use switch RGB and stuff like that?

This seems to be the user data equivalent-

This seems to be the best switch RGB equivalent-

Just plug em in like this - just like Arnold

And ta da...attributes and collections targeting different bits of a crowd!