Intro

Unreal Engine 5 documentation on Groom is very shallow and not particularly helpful so the info here is based purely on testing I’ve done.

Enabling Simulation

Gravity Preloading - Makes the hair retain the original shape. Tries to blend the hair back to the original shape when resting. Needs more testing.

Force Visible - Shows the collision wires.

Air Drag - Increases air resistance. Use really low values (around 0.1 or less), too much drag will make the hair stiff and motionless.

Solvers

Solvers seem to behave the opposite way of what their parameter names describes. Solve Bend unbends and Solve Stretch “unstretches” (Is that even a word?).

Bend Solver

Solve Bend - Leave on. Applies a force to return the hair to the original shape. Low dampening and stiffness you can get a natural simulated rest position. It won’t look like the original groom but close.

Project Bend - It blends the solve with the original shape, helps snap the hair back to the original groom.

Bend Dampening - High values prevent the hair snapping to the original shape. Lower the value if the hair is snapping back into shape too fast, higher if its losing shape. Keep it start at 0.005 and tweak.

Bend Stiffness - Higher the value the less the hair will deform.

Stretch Solver

Allows the hair length to change, I didn’t find it particularly helpful so I leave it off. Not sure if it is a good practice. Stretch follows the same logic as bend.

Keeping the stiffness at 100 will prevent the hair from stretching.

Collision Constraints

This part makes very little sense to me. More testing needed.