Bullet API in dart

phys.dart

import 'dart:io';
import 'dart-ext:phys';
import 'dart:typed_data';
import 'package:vector_math/vector_math.dart';

class World {
  int _p;
  
  World() {
    _p = _n_construct();
    _n_init_lazy(_p);
  }
  
  void setGravity(Vector3 vec) {
    _n_set_gravity(_p, vec.x, vec.y, vec.z);
  }
  
  void addRigidBody(RigidBody r) {
    _n_add_rigid_body(_p, r._p);
  }
  
  void step(double dt, [int substeps = 1]) {
    _n_step(_p, dt, substeps);
  }
  
  int _n_construct() native "world_construct";
  void _n_init_lazy(int p) native "world_init_lazy";
  void _n_set_gravity(int p, double x, double y, double z) native "world_set_gravity";
  void _n_add_rigid_body(int p, int pr) native "world_add_rigid_body";
  void _n_step(int p, double dt, int substeps) native "world_step";
}

abstract class CollisionShape {
  int _p;
  
  Vector3 calculateInertia(double mass) {
    List<double> out = new List<double>(3);
    _n_calc_inertia(_p, mass, out);
    return new Vector3(out[0], out[1], out[2]);
  }
  
  int _n_calc_inertia(int p, double mass, List<double> data) native "shape_calc_inertia";
}

class EmptyShape extends CollisionShape {
  EmptyShape() {
    _p = _n_construct();
  }
  
  int _n_construct() native "shape_construct";
}

class StaticPlaneShape extends CollisionShape {
  StaticPlaneShape([Vector3 planeNormal, double planeConstant = 1.0]) {
    planeNormal ??= new Vector3(0.0, 0.0, 0.0);
    _p = _n_construct(planeNormal.x, planeNormal.y, planeNormal.z, planeConstant);
  }
  
  int _n_construct(double x, double y, double z, double pc) native "shape_static_plane_construct";
}

class SphereShape extends CollisionShape {
  SphereShape(double radius) {
    _p = _n_construct(radius);
  }
  
  int _n_construct(double rad) native "shape_sphere_construct";
}

class MotionState {
  int _p;
  
  MotionState([Vector3 pos, Quaternion angle]) {
    pos ??= new Vector3(0.0, 0.0, 0.0);
    angle ??= new Quaternion.identity();
    _p = _n_construct(pos.x, pos.y, pos.z, angle.x, angle.y, angle.z, angle.w);
  }

  Vector3 get pos {
    List<double> data = new List<double>(3);
    _n_get_pos(_p, data);
    return new Vector3(data[0], data[1], data[2]);
  }

  set pos(Vector3 v) {
    _n_set_pos(_p, v.x, v.y, v.z);
  }

  Quaternion get angle {
    List<double> data = new List<double>(4);
    _n_get_angle(_p, data);
    return new Quaternion(data[0], data[1], data[2], data[3]);
  }

  set angle(Quaternion v) {
    _n_set_angle(_p, v.x, v.y, v.z, v.w);
  }

  void _n_get_pos(int p, List<double> data) native "motion_state_get_pos";
  void _n_set_pos(int p, double x, double y, double z) native "motion_state_set_pos";
  void _n_get_angle(int p, List<double> data) native "motion_state_get_angle";
  void _n_set_angle(int p, double x, double y, double z, double w) native "motion_state_set_angle";
  
  int _n_construct(double x, double y, double z, double qx, double qy, double qz, double qw) native "motion_state_construct";
}

class RigidBody {
  MotionState motionState;
  CollisionShape shape;
  
  int _p;
  
  RigidBody({double mass, this.motionState, this.shape, Vector3 inertia, double restitution, double friction}) {
    restitution ??= 0.1;
    friction ??= 0.5;
    mass ??= 1.0;
    motionState ??= new MotionState();
    shape ??= new EmptyShape();
    inertia ??= shape.calculateInertia(mass);
    _p = _n_construct(mass, motionState._p, shape._p, inertia.x, inertia.y, inertia.z, restitution, friction);
  }
  
  int _n_construct(double mass, int pMotionState, int pCollisionShape, double x, double y, double z, double restitution, double friction) native "rigid_body_construct";
}

void main() {
  var w = new World();
  w.setGravity(new Vector3(0.0, -10.0, 0.0));
  
  var planeShape = new StaticPlaneShape(new Vector3(0.0, 1.0, 0.0));
  var planeBody = new RigidBody(shape: planeShape, mass: 0.0, restitution: 0.9);
  w.addRigidBody(planeBody);
  
  var ballShape = new SphereShape(1.0);
  var ballMotionState = new MotionState(new Vector3(0.0, 30.0, 0.0));
  var ballBody = new RigidBody(shape: ballShape, motionState: ballMotionState, mass: 1.0, restitution: 0.5);
  w.addRigidBody(ballBody);
  
  for (int i = 0; i < 300; i++) {
    w.step(1 / 60, 10);
    print("${ballMotionState.pos.y}");
  }
}