Turtle Verbs & the Step Program

▶ Live demo: run this tutorial — built from src/02_turtle_verbs.ts.

The agent.* verbs are the Taos Engine turtle vocabulary, and the step array is the per-agent program — the GPU equivalent of turtles.ask(...). This demo has agents seek the world center and then orbit it, exercising face, towards, distance, turn, and moveForward together.

The verb catalog (AgentScript → Taos Engine)#

Movement & heading:

Sensing a patch field (tutorial 3): agent.sense(f), agent.senseAhead(f, d), agent.senseAt(f, d, angle), agent.steer(f, …).

Neighbors (tutorial 4): agent.neighborCenter/Velocity/Separation/Count(r), agent.nearest(r), agent.neighborsAhead(r, halfAngle).

A target is any vec3 expression — expr.vec3(0,0,0) for a fixed point, or a neighbor query, or another agent's position. Heading lives on the XZ plane.

Branching and the step program#

step is an array of Actions run top to bottom, each compiled to WGSL. Use action.if_(cond, [...], [...else]) to branch and action.set(attr, value) to write an attribute. The seek-then-orbit logic:

const center = expr.vec3(0, 0, 0);
step: [
  agent.face(center),                                    // point at the center
  action.if_(expr.gt(agent.distance(center), RING), [
    agent.moveForward(16),                               // far → drive straight in
  ]),
  action.if_(expr.le(agent.distance(center), RING), [
    agent.turn(1.5),                                     // close → ~tangent → orbit
    agent.moveForward(9),
  ]),
  agent.turn(agent.randomTurn(0.05)),                    // a little shimmer
],

Reads see the start-of-frame snapshot; writes within one step apply in order (so face then moveForward does what you'd expect). This is the deliberate, well-defined version of AgentScript's ask ordering.

Edge topologies#

For position-movement models, the world boundary is appended to your step automatically. Pick it with world.topology:

This demo uses 'bounce' so the wanderers that escape the ring turn back.

Next#

• Tutorial 3 — Patches & Stigmergy: the grid agents sense and deposit into — the slime-mold model.