The default behavior of 3ds Max hair is to render as a post process in a "Render Effect". MAXtoA does not support Render Effects, so this will not work. To use 3ds Max hair in MAXtoA, we must tell the 3ds Max Hair plugin to output renderer-native hairs. Unfortunately, the Hair plugin does not know about MAXtoA or Arnold, and the option to turn this on ("mr_prim") can be found in the render effects property rollout.
This can be enabled by doing the following:
- Press the 8 key to bring up the Environment/Effects dialog.
- Choose the Effects tab.
- Choose the Hair & Fur render effect.
- In the render effect rollouts Hair Rendering Options group, choose "mr_prim" as the rendering type.
This will allow hair to render as native Arnold Curves. Arnold will (automatically under the hood) apply the new Standard Hair the standard_hair shader and attempt to map some of the 3ds Max hair material parameters to it. This is a rather poor fit, though, so it yields at best an approximation of the appearance of the 3ds Max hair. A much better option is to create your Standard Hair shader the standard_hair shader in the material editor, and assign it as a custom material in the hair rollout, by drag & dropping it onto it: