Hello everyone,

I noticed recently that the mtlx ambient occlusion node was no longer accessible in Houdini 21 (https://www.sidefx.com/docs/houdini/nodes/vop/mtlxambientocclusion.html). Is there any kind of replacement for it? Having pixel AO on the fly in materials is incredibly valuable to make quick improvements, are we just meant to either bake to attributes (which is limited by the geometry) or bake actual maps in cops (which is much longer, requires UV, has a limited resolution...)?

I use AO in materials so much in my day to day work, I'm a bit confused... Thanks !

The ambient occlusion node was removed from MaterialX, which is why it doesn't show up in Houdini 21. Karma has the ability to generate an AO AOV without doing anything in the material. There is a checkbox in the Karma Render Settings LOP to enable this AOV.

(I'm parroting something I heard yesterday so I may be wrong about this - please post again if I'm inadvertently lying)

While I'm not particularly sad to hear that the materialx AO is gone (it was too barebones to be really useful in shader networks) it also means we now have no way of doing it aside from switching back to VEX based shaders. That, of course, only works on cpu and isn't really an option in my opinion. An AO AOV can't replace that either, that is for an entirely different purpose. We definitely need a different solution in Karma that is more useful and works on both CPU and GPU renderers.