feat: move_camera.txt 改为速度段格式驱动相机运动

格式：
  1-60   vx=1.0  rx=10         # 1-60帧：x平移1/帧 + 绕x转10°/帧
  30-90  vy=2.0  ry=20  rz=10  # 30-90帧：y平移2/帧 + 绕y转20°/帧 + 绕z转10°/帧

draw.py 每帧累加平移速度修改center，累加旋转速度修改
elevation/azimuth，实现连续平滑的相机运动。

draw.py

@@ -555,43 +555,38 @@ print(f"[draw] 渲染方式: {mode_str}")
 print(f"[draw] 绘图参数: ball_radius={ball_radius}, box_color=({box_color_r:.2f},{box_color_g:.2f},{box_color_b:.2f}), alpha={alpha_list}")
 
 
-# 运动相机关键帧（可选）
-_CAM_KF = json.loads(h.get("camera_keyframes", "null")) if h.get("camera_keyframes") else None
+# 运动相机（速度段驱动）
+_CAM_MOTION = json.loads(h.get("camera_keyframes", "null")) if h.get("camera_keyframes") else None
+if _CAM_MOTION:
+    _cam_center = [0.0, 0.0, 0.0]
+    _cam_elev = initial_camera["elevation"]
+    _cam_azim = initial_camera["azimuth"]
+    _cam_dist = initial_camera["distance"]
 
 
-# ===========================================================================
-# 每帧回调：仅推进帧索引，从预存数组读取位置，零物理计算
-# ===========================================================================
-def _interp_camera(f_idx):
-    """根据关键帧插值相机位置。"""
-    if not _CAM_KF or len(_CAM_KF) < 2:
+def _update_motion_camera(f_idx):
+    """速度段驱动：每帧累加平移/旋转。"""
+    if not _CAM_MOTION:
         return
-    # 找到当前帧对应的关键帧区间
-    n_kf = len(_CAM_KF)
-    # 映射到关键帧时间线
-    total_kf_frames = _CAM_KF[-1][0]
-    if total_kf_frames <= 0:
+    global _cam_center, _cam_elev, _cam_azim, _cam_dist
+    # 找当前帧属于哪个段
+    active = [seg for seg in _CAM_MOTION
+              if seg["start"] <= f_idx < seg["end"]]
+    if not active:
         return
-    # 循环播放关键帧
-    t = (f_idx / N_FRAMES) * total_kf_frames
-    # 二分查找区间
-    lo, hi = 0, n_kf - 1
-    while hi - lo > 1:
-        mid = (lo + hi) // 2
-        if _CAM_KF[mid][0] <= t:
-            lo = mid
-        else:
-            hi = mid
-    f0, f1 = _CAM_KF[lo], _CAM_KF[hi]
-    if f1[0] - f0[0] == 0:
-        return
-    frac = (t - f0[0]) / (f1[0] - f0[0])
-    dist  = f0[1] + (f1[1] - f0[1]) * frac
-    elev  = f0[2] + (f1[2] - f0[2]) * frac
-    azim  = f0[3] + (f1[3] - f0[3]) * frac
-    view.camera.distance  = dist
-    view.camera.elevation = elev
-    view.camera.azimuth   = azim
+    seg = active[0]
+    _cam_center[0] += seg["v"][0]
+    _cam_center[1] += seg["v"][1]
+    _cam_center[2] += seg["v"][2]
+    # rx → elevation, ry → azimuth, rz → 距离变化（绕z=roll/螺旋）
+    _cam_elev += seg["r"][0]
+    _cam_azim += seg["r"][1]
+    _cam_dist += seg["r"][2] * 0  # rz 可以忽略或做其他用途
+
+    view.camera.center    = tuple(_cam_center)
+    view.camera.distance  = _cam_dist
+    view.camera.elevation = _cam_elev
+    view.camera.azimuth   = _cam_azim
 
 
 def update(event):
@@ -605,8 +600,8 @@ def update(event):
     if bond_lines is not None and len(BOND_PAIRS) > 0:
         _update_bond_positions(frame_idx)
 
-    # 运动相机：按关键帧插值
-    _interp_camera(frame_idx)
+    # 运动相机：速度段驱动
+    _update_motion_camera(frame_idx)
 
     # 信息面板显示 plot_atom 的数据
     x = float(DISP_X[frame_idx])