UPDATE: two ball dataset

dataset/multi_bb/multi_bb_2025-11-18_20-08-18.npz

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:7450a9cdabff9537081a228e37eefcb3a29469ed9ff32aa562148160718e5eaf
+size 63591971

dataset/multi_bb/multi_bb_2025-11-18_20-08-18_metadata.pkl

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:d53710d0992110467de164e14be85f1307ab9cf3dac3d84df4ae428e6e0970b2
+size 478

multi_bb_collect.py

@@ -16,6 +16,7 @@ from dataset import TrajectoryBuffer
 class Config:
     """Configuration for the multi-ball-in-bottle environment."""
 
+    num_balls: int = 4
     bottle_length: float = 0.10  # x dimension (m)
     bottle_width: float = 0.10  # y dimension (m)
     bottle_height: float = 0.50  # z dimension (m)
@@ -60,7 +61,7 @@ class BottleMultiBallEnv:
         # Cache indices for qpos/qvel blocks of each ball
         self.ball_qpos_idx = []
         self.ball_qvel_idx = []
-        for i in range(1, 5):
+        for i in range(1, self.config.num_balls + 1):
             name = f"ball{i}_free"
             self.ball_qpos_idx.append(
                 self.model.jnt_qposadr[mujoco.mj_name2id(self.model, mujoco.mjtObj.mjOBJ_JOINT, name)]
@@ -97,7 +98,7 @@ class BottleMultiBallEnv:
                 <geom name="wall_yp" type="box" pos="0 {half_wid + t/2} {h/2}" size="{half_len} {t/2} {h/2}" rgba="0.7 0.7 0.7 1"/>
                 <geom name="wall_yn" type="box" pos="0 -{half_wid + t/2} {h/2}" size="{half_len} {t/2} {h/2}" rgba="0.7 0.7 0.7 1"/>
                 <!-- Balls (each as a root body because free joints must be root-level) -->
-                {"".join([self._ball_body_xml(i, ball_rad) for i in range(1, 5)])}
+                {"".join([self._ball_body_xml(i, ball_rad) for i in range(1, self.config.num_balls + 1)])}
                 <camera name="bottle_cam" pos="0 0 {h}" quat="0 -1 0 0" fovy="60"/>
             </worldbody>
             <asset>
@@ -124,7 +125,7 @@ class BottleMultiBallEnv:
         positions = self._sample_initial_positions()
         velocities = self._sample_initial_velocities()
 
-        for i in range(4):
+        for i in range(self.config.num_balls):
             qpos_idx = self.ball_qpos_idx[i]
             qvel_idx = self.ball_qvel_idx[i]
             pos = positions[i]
@@ -143,7 +144,7 @@ class BottleMultiBallEnv:
         positions = []
         margin = c.ball_radius * 2.5
         tries = 0
-        while len(positions) < 4:
+        while len(positions) < c.num_balls:
             x = self.rng.uniform(-c.bottle_length / 2 + margin, c.bottle_length / 2 - margin)
             y = self.rng.uniform(-c.bottle_width / 2 + margin, c.bottle_width / 2 - margin)
             z = self.rng.uniform(c.min_z, c.max_z)
@@ -157,8 +158,8 @@ class BottleMultiBallEnv:
 
     def _sample_initial_velocities(self) -> np.ndarray:
         c = self.config
-        speeds = self.rng.uniform(0.0, c.max_xy_speed, size=(4,))
-        angles = self.rng.uniform(0.0, 2 * np.pi, size=(4,))
+        speeds = self.rng.uniform(0.0, c.max_xy_speed, size=(c.num_balls,))
+        angles = self.rng.uniform(0.0, 2 * np.pi, size=(c.num_balls,))
         vx = speeds * np.cos(angles)
         vy = speeds * np.sin(angles)
         vz = np.zeros_like(vx)
@@ -172,7 +173,7 @@ class BottleMultiBallEnv:
         # Collect positions and velocities for four balls
         pos_list: List[np.ndarray] = []
         vel_list: List[np.ndarray] = []
-        for i in range(4):
+        for i in range(self.config.num_balls):
             qpos_idx = self.ball_qpos_idx[i]
             qvel_idx = self.ball_qvel_idx[i]
             pos_list.append(self.data.qpos[qpos_idx : qpos_idx + 3].copy())
@@ -265,6 +266,7 @@ def parse_args():
     parser.add_argument("--headless", action="store_true", help="Disable on-screen rendering")
     parser.add_argument("--realtime", action="store_true", help="Sleep to match real time")
     parser.add_argument("--demo", action="store_true", help="Run a short demo instead of full collection")
+    parser.add_argument("--num_balls", type=int, default=2, help="Number of balls in the bottle")
     return parser.parse_args()
 
 
@@ -272,7 +274,7 @@ def main():
     args = parse_args()
     np.random.seed(args.seed)
 
-    config = Config()
+    config = Config(num_balls=args.num_balls)
     env = BottleMultiBallEnv(headless=args.headless, config=config, seed=args.seed)
 
     try: