Mtlx ambient occlusion karma (materialX) in Houdini

Mtlx ambient occlusion karma (materialX)

add karma material builder node and dive inside add mtlx ambient occlusion node (to convert float to color) add mtlx convert node signature: float(color) add mtlx invert node plug it into opacity channel of mtlxstandardsurface (the mtlx ambient occlusion node currently only works with Karma CPU)

alternative workflow for Karma XPU (shadow on floor)

create an uniform shadow on a plain white background using a single env light render this as phantom object with karmaXPU (to hide the geo and just leave the shadow) in comp, convert the color channel (C) to alpha (A) to get the shadow pass