Hi, and welcome to my ever expanding list of problems I create for myself in Unreal Engine (5.2) by being unbelievably stubborn and unwilling to turn around and doing things in an easier way!
Lately, I've been experimenting with grooms, as part of a character redesign I'm working on, which used to have sculpted fur instead. I made the guides using Maya's Xgen, and exported it using Alembic for Grooms
in order to get it to work in Unreal Engine with hair UVs. Disregarding the weird lighting in interior scenes, and bad deformation when animated for a moment, the groom itself looks pretty good:
^ This is the best lighting I can get at this time, and with the exception of the somewhat blotchy shadows in the chest area, it's not bad. However, this is using a large number of light sources for this specific angle and pose, so it's obviously never going to work in any real in-game scenario. This is where we get to the bad lighting and deformation (never mind the red arrows, it took me forever to figure out how to make eye joint rotations drive the planar eyes' texture offset so he can look at things):
^ Left is not using RBF interpolation, right is with RBF on. Without RBF, it looks mostly okay without simulation, because simulation makes the fur jittery in certain areas for whatever reason. However, the blendshape I use to make him smirk makes the fur spin out of control in that area. I have no idea why, because while I don't have any way to see the guides in Unreal Engine, the vertex normals look fine:
With RBF interpolation on, it's all just one big mess, so that's quite useless without the right setup, but it doesn't screw up the smirk blendshape like the normal interpolation does. RBF has this weird slot for skeletal meshes, but it won't accept my skeletal mesh:
^ What is this slot, and how do I use it? The description of this slot is absolutely useless, as it refers to things that don't exist in the editor as far as I can tell:
^ What does that even mean?
One possible explanation is that I don't have enough guides, but as far as I can tell, there are no guidelines for how much I can put into a groom before it's no longer viable for any real-time rendering. It's the areas with a low amount where the fur jitters with simulation, so maybe it is a bit low in those areas:
Also, about the lighting, I'm open to the idea that maybe I just don't know how to light a level properly. The thing I'm trying to do here is to create some sort of atmosphere, but not at the expense of visibility in this case. So the way I have lit it is with a bunch of massive light sources in an attempt at evenly lighting the environment. It looks like this. The screenshot from above is from the leftmost balcony:
^ I would love to know if this is the right approach to lighting the way I want, and if there are better alternatives. What is clear, though, is that this lighting approach doesn't seem to work with grooms, as far as I can tell.
Any help would be greatly appreciated!