Sph

Static helpers for SPH simulation and uniform-grid neighbor queries.

Methods

static u64 cellKey(s32 ix, s32 iy, s32 iz)

Packs integer cell coordinates into a single 64-bit key.

ix	Cell index along X
iy	Cell index along Y
iz	Cell index along Z

static f32 smoothingKernel(f32 dist, f32 h)

Linear SPH kernel W(r,h) = max(0, 1 - r/h) / h

dist	Distance between particles
h	Smoothing length

static Vector3 gradientSmoothingKernel(const Vector3& distVec, f32 dist, f32 h)

Gradient of the linear kernel potential used in the JS reference. Algebraically identical to (distVec / |distVec|) * (-|distVec| / h^2) with the magnitudes cancelling: no sqrt, no normalize, no temporaries.

distVec	thisPosition - neighborPosition
dist		distVec
h	Smoothing length

static void step(Particle** particles, u32 n, const f32* positions, f32* density, f32* pressure, f32 h, f32 k, f32 rho0, f32 viscosity, vector<vector<u32>>& cells, const Vector3& halfExtent)

One SPH pass: clears forces, builds the flat grid, density, pressure, then pressure + viscous forces. Reads positions from the contiguous positions[] array (must be in sync with curState.position at call time). Writes pressure and viscous forces into particles[i]->forces. The caller's integration step is expected to add gravity and divide forces by mass to produce acceleration.

particles	Particle pointers (reads mass and curState.velocity, writes forces)
n	Count
positions	Contiguous position buffer (length n*3, xyz interleaved)
density	Per-particle density (length n)
pressure	Per-particle pressure (length n)
h	Smoothing length (cell size = h)
k	Pressure stiffness (JS default 1000)
rho0	Rest density (JS default 1000)
viscosity	Viscosity scale (JS default 0.1)
cells	Reused flat cell array (resized to nxnynz internally)
halfExtent	Half-size of the AABB the simulation lives in

Properties