bo3-js/js/instances/BasePart.js

import * as THREE from "three";
import * as CANNON from "cannon-es";
import { Instance } from "./Instance.js";

export class BasePart extends Instance {
  constructor() {
    super("BasePart");

    // === Visual properties ===
    this.Color = 0x00ff00;
    this.Size = new THREE.Vector3(1, 1, 1);
    this.Position = new THREE.Vector3(0, 0, 0);
    this.Orientation = new THREE.Euler(0, 0, 0);
    this.Anchored = false; // Roblox-style toggle

    // === Three.js setup ===
    const geometry = new THREE.BoxGeometry(this.Size.x, this.Size.y, this.Size.z);
    const material = new THREE.MeshStandardMaterial({ color: this.Color });
    this.mesh = new THREE.Mesh(geometry, material);
    this.mesh.castShadow = true;
    this.mesh.receiveShadow = true;
    this.mesh.userData.basePart = this;

    // === Cannon.js setup ===
    const shape = new CANNON.Box(
      new CANNON.Vec3(this.Size.x / 2, this.Size.y / 2, this.Size.z / 2)
    );
    this.body = new CANNON.Body({
      mass: 1,
      position: new CANNON.Vec3(this.Position.x, this.Position.y, this.Position.z),
      shape: shape,
    });
    this.body.userData = { basePart: this };

    this._originalMass = this.body.mass; // store default mass
    this._renderService = null; // assigned when added to scene
  }

  // === Scene lifecycle ===
  OnAddedToScene(parent) {
    const dm = this.GetDataModel();
    const renderService = dm.GetService("RenderService");
    this._renderService = renderService;

    if (renderService.scene) renderService.scene.add(this.mesh);
    if (!renderService.physicsWorld) renderService._initPhysicsWorld();

    renderService.physicsWorld.addBody(this.body);
    this._applyAnchoredState();
  }

  // === Anchoring logic ===
  setAnchored(value) {
    if (this.Anchored === value) return;
    this.Anchored = value;
    this._applyAnchoredState();
  }

  _applyAnchoredState() {
    if (!this.body) return;
    if (this.Anchored) {
      this.body.type = CANNON.Body.STATIC;
      this.body.mass = 0;
      this.body.velocity.set(0, 0, 0);
      this.body.angularVelocity.set(0, 0, 0);
    } else {
      this.body.type = CANNON.Body.DYNAMIC;
      this.body.mass = this._originalMass || 1;
    }
    this.body.updateMassProperties();
  }

  // === Updates ===
  updateVisual() {
    // Only update mesh from physics if not anchored
    if (!this.Anchored) {
      this.mesh.position.copy(this.body.position);
      this.mesh.quaternion.copy(this.body.quaternion);
    }
  }

  updateBodyPosition() {
    this.body.position.set(this.Position.x, this.Position.y, this.Position.z);
    this.body.quaternion.setFromEuler(
      this.Orientation.x,
      this.Orientation.y,
      this.Orientation.z
    );
    this.body.velocity.set(0, 0, 0);
    this.body.angularVelocity.set(0, 0, 0);
  }

  updateSizes() {
    // Update Three geometry
    this.mesh.geometry.dispose();
    this.mesh.geometry = new THREE.BoxGeometry(this.Size.x, this.Size.y, this.Size.z);

    // Update Cannon shape
    this.body.shapes = [];
    const newShape = new CANNON.Box(
      new CANNON.Vec3(this.Size.x / 2, this.Size.y / 2, this.Size.z / 2)
    );
    this.body.addShape(newShape);
    this.body.updateMassProperties();
  }

  OnReplicated() {
    if (this.IsReplicated) {
      this.body.type = CANNON.Body.KINEMATIC;
      this.body.velocity.set(0, 0, 0);
      this.body.angularVelocity.set(0, 0, 0);
    }

    this.body.position.copy(this.Position);
    this.body.quaternion.setFromEuler(
      this.Orientation.x,
      this.Orientation.y,
      this.Orientation.z
    );

    this.updateVisual();
  }

  OnPhysicsTick() {

    if (this.body.position.y < -1000) {
      // Fell out of world, destroy like in Roblox
      this.Destroy();
      console.debug("BasePart fell out of world and was destroyed.");
      return;
    }

    if (this.IsReplicated || this.Anchored) return;

    this.Position.set(
      this.body.position.x,
      this.body.position.y,
      this.body.position.z
    );
    this.Orientation.setFromQuaternion(this.body.quaternion);
  }

  // === Cleanup ===
  Destroy() {
    if (this._renderService) {
      if (this.mesh.parent) this.mesh.parent.remove(this.mesh);
      if (this._renderService.physicsWorld)
        this._renderService.physicsWorld.removeBody(this.body);
    }
    super.Destroy();
  }
}