I have a problem with vellum hair recently encountered. I am working in SOP level and genrated the guides from the hair Geo using UV. Everything went flawless till the the simulation start. Have no idea why I am having this issue.
Ok. I think this is a bug in Houdini 19. Something wrong with vellum hair sim if you choose " Use External Geo" For guides in the guide grooming or even if you choose to have the guides created in SOP. It wont be recognized for some reasons. I've just tested the whole thing in Houdini 18 and it works perfectly.