rift_motes

One step of the arcane mote swarm, run as a sim.shader solver with a neighbour grid. Motes swirl around the rift through a rolling vortex ring stirred by turbulence, and keep apart through grid-based separation, so the swarm streams together with its motes kept apart. It runs one invocation per mote in workgroups of 64.

For each mote the shader builds a desired velocity from four parts:

• a swirl around the vertical axis through the origin, swirl * (0.45 + 1.4 * exp(-0.35 * rho)), fastest near the axis;
• a poloidal roll around the ring core at radius coreR and height coreH: up on the inside, out over the top, down at the outer edge, at a rate set by rollRate;
• a smooth turbulence from summed sines of position and time;
• a pull back toward the ring core for any mote farther than shell from it, and a lift for any mote below height 0.2.

It then visits every mote in the 27 grid cells around it and adds a push away from each neighbour closer than radius, weighted by (1 - distance / radius)^2. The velocity eases toward the desired one at a rate of 1 - exp(-1.6 * dt), takes the push times separate * dt, is capped at 4.5 units per second, and moves the mote by velocity * dt.

Bindings

The grid helpers come from #include "@builtin::systems.procgen.grid".

Parameters

Dispatch

The arcane_rift graph (rift/arcane_rift.procGraph) dispatches it from its swarm node, a sim.shader over 900 points seeded in a cylinder of radius 4.2 and height 3.4, with a v (Vec3) attribute, neighborRadius 0.75 and uniforms radius 0.75, separate 5, coreR 2.5, coreH 1.7, shell 1.9, swirl 1.5 and rollRate 0.5. Each of those 900 leaders is drawn as a cluster of eight motes by rift_mote_cluster. In the Procgen Effects Showcase world, the fx_rift scene plays the graph.