I am aware that FP automatically creates its own and if Im lucky with a supported engine, it will work. I have already created another set of materials as multi-sub due to the un-supported render engine. I would assume it would be just as easy to use my existing m-sub? I may have fixed it by updating FP. Either that or before dragging my multi-sub over to FP, I made sure I had the same amount of material ID slots as the one that FP created.
You can assign your own multi-sub manually, but it will be overriden by the generated by Forest. To avoid that, you should turn off Geometry->"Consolidate Materials".
But as said, we suggest to not use this procedure, and let to Forest to handle the multi-sub by itself.
As far as assigning materials to source objects, if you mean un-hiding and un-freezing source objects, that seems more labor intensive that just dragging the material to the FP slot.
Alternatively, you can assign the materials to "Geometry->Material". There is an entry for each source object, and it overrides the object's material.
Since one or other method are time consuming, the better approach is to prepare your object and materials only one time, and
save them in the library as presets.
EDIT: Unfortunately it is presenting more problems that Ive run into before with un-supported render engines. It consistently tells me that There are too many faces in the scene even with the parameter cranked up to 9999million. Ill have to resort to TyFlow for scattering for now. Ty.
What render engine do you use ?
You can set any limit (as Max.Faces) to zero to disable it.
Anyway, generating an huge geometry is not a good idea, because it is very likely that Max or the render engine crashes, due to overload.
In these cases, you can use
Forest Tools to generate standalone objects.