As I remember, there is a way to bake a texture as vertex colors. What you'd need to do is to simply bake it as a texture first, then assign it into a material as a texture. Then in the vertex paint modifier, there is a button to make vertex colors from that texture.
Anyone knows a functioning way to bake AO onto the vertex colors of an object within 3dsmax? All the old ways either don't work, or are incredibly buggy on Max2016. Tried a few scripts too, none of them work. Can't believe I'm scratching my head with something that should be so simple?
There's the Peaks and Pits maxscript which works okay (but only on Editable Meshes), and you can bake Radiosity using the Vertex Paint modifier. I do prefer the former though, if it'd only be upgraded by somebody more knowledgeable in the arcane ways of the Maxscript than me.