fix: driven atoms now oscillate around their initial equilibrium position

Previously, apply_driving_force set absolute position to A*cos(2π f t + φ),
ignoring the atom's initial coordinates. For atoms not at the origin (e.g.,
atom 120 at x=119), this incorrectly forced them back toward the origin each
step, causing severe distortion and numerical explosion.

Fix: store each driven atom's initial position as eq_pos/eq_x/eq_y/eq_z at
load time; position is now eq + A*cos(2π f t + φ) in all four engines
(Python, C, C++, Fortran).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

compute.py

@@ -69,6 +69,12 @@ camera_keyframes_raw = ""
 camera_distance = 40.0
 camera_elevation = 0.0
 camera_azimuth = 0.0
+camera_center_x = 0.0
+camera_center_y = 0.0
+camera_center_z = 0.0
+camera_pos_x = None
+camera_pos_y = None
+camera_pos_z = None
 FIXED_MASK_X = None
 FIXED_MASK_Y = None
 FIXED_MASK_Z = None
@@ -649,6 +655,8 @@ def load_driver_file(driver_path, atom_ids):
                 "phi": phi_rad,
                 "period_str": period_str,
                 "period_cycles": None if period_str == "all" else float(period_str),
+                # 平衡位置（原子初始坐标），驱动为相对于此位置的偏移
+                "eq_pos": None,
                 # 在模拟中动态记录：冻结步数索引、冻结位置
                 "freeze_step": None,
                 "freeze_pos": None,
@@ -698,8 +706,9 @@ def apply_driving_force(x, y, z, vx, vy, vz, t, step, drivers, dt):
         else:
             period_steps = None  # 全程驱动
 
-        # 当前驱动力下的位置 / 速度
-        pos_drive = d["amp"] * np.cos(2.0 * np.pi * d["freq"] * t + d["phi"])
+        # 当前驱动力下的位置 / 速度（偏移叠加在初始平衡坐标上）
+        eq = d["eq_pos"] if d["eq_pos"] is not None else np.zeros(3)
+        pos_drive = eq + d["amp"] * np.cos(2.0 * np.pi * d["freq"] * t + d["phi"])
         vel_drive = -d["amp"] * 2.0 * np.pi * d["freq"] * np.sin(2.0 * np.pi * d["freq"] * t + d["phi"])
 
         x[idx] = pos_drive[0]
@@ -764,6 +773,8 @@ def run_from_config(config, out_dir=None):
     global ball_radius, ball_color_r, ball_color_g, ball_color_b
     global box_color_r, box_color_g, box_color_b
     global use_marker, camera_keyframes_raw, camera_distance, camera_elevation, camera_azimuth
+    global camera_center_x, camera_center_y, camera_center_z
+    global camera_pos_x, camera_pos_y, camera_pos_z
     global FIXED_MASK_X, FIXED_MASK_Y, FIXED_MASK_Z
     global warmup_steps, sample_start, sample_end
     global GRAVITY_FIELD, GRAVITY_INTERACTION, ELASTIC_FORCE, DAMPING_FORCE, GRAVITY_STRENGTH
@@ -832,6 +843,12 @@ def run_from_config(config, out_dir=None):
     camera_distance = float(config.get("camera_distance", 40.0))
     camera_elevation = float(config.get("camera_elevation", 0.0))
     camera_azimuth = float(config.get("camera_azimuth", 0.0))
+    camera_center_x = float(config.get("camera_center_x", 0.0))
+    camera_center_y = float(config.get("camera_center_y", 0.0))
+    camera_center_z = float(config.get("camera_center_z", 0.0))
+    camera_pos_x = config.get("camera_pos_x", None)
+    camera_pos_y = config.get("camera_pos_y", None)
+    camera_pos_z = config.get("camera_pos_z", None)
 
     # 力开关
     global GRAVITY_FIELD, GRAVITY_INTERACTION, ELASTIC_FORCE, DAMPING_FORCE, GRAVITY_STRENGTH
@@ -851,6 +868,15 @@ def run_from_config(config, out_dir=None):
         if out_dir is not None and not os.path.isabs(driver_rel):
             driver_path = os.path.join(out_dir, driver_rel)
         DRIVER_DATA = load_driver_file(driver_path, ATOM_IDS)
+        # 将每个驱动原子的初始坐标作为平衡位置
+        if DRIVER_DATA:
+            for _d in DRIVER_DATA:
+                _i = _d["atom_index"]
+                _d["eq_pos"] = np.array([
+                    ATOM_POSITIONS[_i, 0],
+                    ATOM_POSITIONS[_i, 1],
+                    ATOM_POSITIONS[_i, 2],
+                ], dtype=np.float64)
 
     # 加载运动相机关键帧
     camera_keyframes_raw = ""
@@ -986,6 +1012,9 @@ def run_engine(engine, input_dir, output_dir, config):
         "camera_distance": float(config.get("camera_distance", 40.0)),
         "camera_elevation": float(config.get("camera_elevation", 0)),
         "camera_azimuth": float(config.get("camera_azimuth", 0)),
+        "camera_center_x": float(config.get("camera_center_x", 0.0)),
+        "camera_center_y": float(config.get("camera_center_y", 0.0)),
+        "camera_center_z": float(config.get("camera_center_z", 0.0)),
     }
     param_path = os.path.join(script_dir, "engines", engine, "param.json")
     os.makedirs(os.path.dirname(param_path), exist_ok=True)
@@ -1136,12 +1165,27 @@ def run_engine(engine, input_dir, output_dir, config):
         _npz_path = disp_path.replace("display.txt", "display.npz")
         try:
             _d = load_display_txt(disp_path)
+            # 外部引擎不写摄像机参数到 display.txt，在此从全局变量补入
+            _cam_extra = {
+                "camera_distance":  str(camera_distance),
+                "camera_elevation": str(camera_elevation),
+                "camera_azimuth":   str(camera_azimuth),
+                "camera_center_x":  str(camera_center_x),
+                "camera_center_y":  str(camera_center_y),
+                "camera_center_z":  str(camera_center_z),
+                "camera_keyframes": str(camera_keyframes_raw),
+            }
+            if camera_pos_x is not None:
+                _cam_extra["camera_pos_x"] = str(camera_pos_x)
+                _cam_extra["camera_pos_y"] = str(camera_pos_y)
+                _cam_extra["camera_pos_z"] = str(camera_pos_z)
             save_display_npz(
                 _npz_path,
                 _d["frames_x"], _d["frames_y"], _d["frames_z"],
                 _d["frames_vx"], _d["frames_vy"], _d["frames_vz"],
                 _d["atom_ids"],
                 header_fields={**_d["header_fields"],
+                                **_cam_extra,
                                 "number_of_frames": str(_d["n_total_frames"]),
                                 "number_of_particles": str(_d["n_total_particles"])})
             print(f"[compute] display.npz 已生成: {_npz_path}")
@@ -1727,6 +1771,14 @@ def run_simulation(save_trajectory=0):
                        "camera_distance": str(camera_distance),
                        "camera_elevation": str(camera_elevation),
                        "camera_azimuth": str(camera_azimuth),
+                       "camera_center_x": str(camera_center_x),
+                       "camera_center_y": str(camera_center_y),
+                       "camera_center_z": str(camera_center_z),
+                       **({
+                           "camera_pos_x": str(camera_pos_x),
+                           "camera_pos_y": str(camera_pos_y),
+                           "camera_pos_z": str(camera_pos_z),
+                       } if camera_pos_x is not None else {}),
                        "camera_keyframes": str(camera_keyframes_raw)}
     )
     print(f"[compute] display.txt 已保存至: {disp_path} ({n_frames_actual} 帧)")
@@ -1765,6 +1817,9 @@ def run_simulation(save_trajectory=0):
             "camera_distance": str(camera_distance),
             "camera_elevation": str(camera_elevation),
             "camera_azimuth": str(camera_azimuth),
+            "camera_center_x": str(camera_center_x),
+            "camera_center_y": str(camera_center_y),
+            "camera_center_z": str(camera_center_z),
             "camera_keyframes": str(camera_keyframes_raw),
             "number_of_frames": str(record_steps),
             "number_of_particles": str(n_atoms)}