Hair
Turn curves into strands that swing, bend and collide, keeping their length so they never stretch into spaghetti.
The Hair Sim node takes strands, curves or point chains, and simulates them. Each strand keeps its length, resists bending, and bumps into the colliders and surfaces around it. Use it for hair, fur, grass, ropes, wires, or any long flexible thing.
Feeding it strands
Hair works on curves: chains of points where each point follows the one before it. Lay out the strands first by scattering roots, drawing guides or growing curves, then wire them into simulation.hair. Put the node in a feedback loop so motion carries from frame to frame. Strands feed straight in and the conversion is automatic.
The first point of every strand is the root and is held in place. That is what pins hair to a scalp and grass to the ground while the rest of the strand swings free.
What the solver does
Three forces shape every strand, all resolved together each cook.
Length. Segments stay the length they started at, so strands never stretch or collapse. This inextensibility is what keeps hair looking like hair.
Bend. Strands resist kinking and return toward their rest shape. More bend resistance gives stiff bristles, less gives soft, floppy locks.
Collisions. Strands push out of colliders, surfaces, and optionally each other.
Everything runs on the GPU and updates live during playback, so bend and damping can be dialled while watching the result move.
Parameters
Colliding with the world
Wire colliders and surfaces into the physics setup and hair respects them: grass parting around a rolling ball, fur pressing against a body. A Force Field adds wind, turbulence, or a gust on a beat.
Dense strands with many segments are the heaviest case for the solver. If motion looks unstable on very fine hair, reduce the segment count per strand or raise the solver's iterations. See Making it faster.