refactor: move world concepts into engine

engine/world/CharacterController.ts

@@ -0,0 +1,89 @@
+import type { Vec3 } from "../math/Vec3"
+import { CollisionWorld, type CollisionWorld as World } from "./CollisionWorld"
+
+export type Character = {
+  position: Vec3
+  yaw: number
+  velocityY: number
+  onGround: boolean
+}
+
+export type CharacterInput = {
+  forward: number
+  right: number
+  jump: boolean
+  run: boolean
+}
+
+export type CharacterConfig = {
+  radius: number
+  speed: number
+  runMultiplier: number
+  gravity: number
+  jumpSpeed: number
+  eyeHeight: number
+}
+
+export namespace CharacterController {
+  export function update(
+    character: Character,
+    input: CharacterInput,
+    dt: number,
+    world: World,
+    config: CharacterConfig,
+  ): void {
+    if (input.jump && character.onGround) {
+      character.velocityY = config.jumpSpeed
+      character.onGround = false
+    }
+    const steps = moveSubsteps(input, dt, config)
+    for (let i = 0; i < steps; i++) {
+      moveHorizontal(character, input, dt / steps, config)
+      CollisionWorld.pushOut(world, character.position, config.radius)
+    }
+    character.velocityY -= config.gravity * dt
+    character.position.y += character.velocityY * dt
+    const ground = CollisionWorld.groundHeight(world, character.position)
+    if (character.position.y <= ground) {
+      character.position.y = ground
+      character.velocityY = 0
+      character.onGround = true
+    } else {
+      character.onGround = false
+    }
+  }
+
+  function moveSubsteps(
+    input: CharacterInput,
+    dt: number,
+    config: CharacterConfig,
+  ): number {
+    const distance =
+      config.speed *
+      runFactor(input, config) *
+      dt *
+      Math.hypot(input.forward, input.right)
+    return Math.max(1, Math.ceil(distance / config.radius))
+  }
+
+  function moveHorizontal(
+    character: Character,
+    input: CharacterInput,
+    dt: number,
+    config: CharacterConfig,
+  ): void {
+    const speed = config.speed * runFactor(input, config) * dt
+    const forwardX = Math.sin(character.yaw)
+    const forwardZ = -Math.cos(character.yaw)
+    const rightX = Math.cos(character.yaw)
+    const rightZ = Math.sin(character.yaw)
+    character.position.x +=
+      (forwardX * input.forward + rightX * input.right) * speed
+    character.position.z +=
+      (forwardZ * input.forward + rightZ * input.right) * speed
+  }
+
+  function runFactor(input: CharacterInput, config: CharacterConfig): number {
+    return input.run ? config.runMultiplier : 1
+  }
+}