diff --git a/WebSite/src/App.tsx b/WebSite/src/App.tsx
index d269e62..01e25a7 100644
--- a/WebSite/src/App.tsx
+++ b/WebSite/src/App.tsx
@@ -819,7 +819,6 @@ export default function App() {
           maxAngle: videoMaxAngle,
           durationSeconds: videoDuration,
           showArrow: showVideoArrow,
-          sourceLabel: selectedVideoSource.label,
         })
       }) as BackendJob;
       setVideoJob(job);
@@ -1069,8 +1068,8 @@ export default function App() {
                   </div>
                   <div className="grid grid-cols-2 gap-4">
                     <div>
-                      <div className="flex justify-between text-[10px] font-bold mb-2 text-slate-500"><span>播放轴向</span><span>Z</span></div>
-                      <div className="h-5 flex items-center text-[10px] font-bold text-slate-400">逐层播放 DICOM 切片</div>
+                      <div className="flex justify-between text-[10px] font-bold mb-2 text-slate-500"><span>最大角度</span><span>{videoMaxAngle}°</span></div>
+                      <input type="range" min="5" max="30" step="1" value={videoMaxAngle} onChange={e => setVideoMaxAngle(parseInt(e.target.value, 10))} className="w-full accent-blue-600" />
                     </div>
                     <div>
                       <div className="flex justify-between text-[10px] font-bold mb-2 text-slate-500"><span>时长</span><span>{videoDuration}s</span></div>
diff --git a/generate_head_extension_video.py b/generate_head_extension_video.py
index 7228ed8..9190ae4 100644
--- a/generate_head_extension_video.py
+++ b/generate_head_extension_video.py
@@ -5,11 +5,13 @@ from pathlib import Path
 import imageio.v2 as imageio
 import numpy as np
 from PIL import Image, ImageDraw, ImageFont
+from scipy.ndimage import map_coordinates
 
 from head_extension_app import (
-    ct_window,
+    crop_head_neck,
     fit_image,
     load_dicom_volume,
+    sagittal_mip,
 )
 
 
@@ -20,6 +22,47 @@ DURATION_SECONDS = 6
 END_HOLD_SECONDS = 1
 
 
+def video_soft_bend_2d(image, angle_degrees):
+    """Video-only 2D deformation with a broad neck transition.
+
+    The app's fast preview uses a compact transition, which is useful for
+    interactive feedback but can visibly split vertebrae in animation. This
+    broad ramp keeps the head and upper cervical spine moving together and
+    blends gradually into the lower neck/shoulder region.
+    """
+    arr = np.asarray(image.convert("L")).astype(np.float32)
+    height, width = arr.shape
+    yy, xx = np.mgrid[0:height, 0:width]
+
+    pivot_x = int(width * 0.55)
+    pivot_y = int(height * 0.62)
+
+    # Broad transition: nearly full motion for head/upper C-spine, then a long
+    # smooth blend through the lower C-spine to avoid splitting bone structures.
+    full_motion_y = height * 0.50
+    fixed_y = height * 0.92
+    t = np.clip((yy - full_motion_y) / (fixed_y - full_motion_y), 0, 1)
+    weight = 1 - (t * t * (3 - 2 * t))
+
+    # A small x-dependent term keeps the posterior contour from looking like a
+    # straight sliced plane while remaining deterministic and smooth.
+    x_soft = np.clip((xx - width * 0.15) / (width * 0.75), 0, 1)
+    x_soft = x_soft * x_soft * (3 - 2 * x_soft)
+    weight = np.clip(weight * (0.90 + 0.10 * x_soft), 0, 1)
+
+    theta = np.deg2rad(angle_degrees) * weight
+    cos_t = np.cos(theta)
+    sin_t = np.sin(theta)
+    dx = xx - pivot_x
+    dy = yy - pivot_y
+
+    src_x = pivot_x + cos_t * dx + sin_t * dy
+    src_y = pivot_y - sin_t * dx + cos_t * dy
+
+    warped = map_coordinates(arr, [src_y, src_x], order=1, mode="constant", cval=0)
+    return Image.fromarray(np.clip(warped, 0, 255).astype(np.uint8)).convert("RGB")
+
+
 def get_font(size):
     for path in [r"C:\Windows\Fonts\arial.ttf", r"C:\Windows\Fonts\calibri.ttf"]:
         if os.path.exists(path):
@@ -27,48 +70,61 @@ def get_font(size):
     return ImageFont.load_default()
 
 
-def make_frame(slice_image, slice_index, slice_count, source_label, show_arrow=True):
+def smoothstep(t):
+    return t * t * (3 - 2 * t)
+
+
+def make_frame(before_image, angle, max_angle, show_arrow=True):
+    after_image = video_soft_bend_2d(before_image, angle)
+
     frame = Image.new("RGB", (1920, 1080), (0, 0, 0))
     draw = ImageDraw.Draw(frame)
 
-    panel = fit_image(slice_image, 1160, 860)
-    frame.paste(panel, (380, 145))
+    left = fit_image(before_image, 760, 720)
+    right = fit_image(after_image, 760, 720)
+    frame.paste(left, (120, 245))
+    frame.paste(right, (1040, 245))
 
     title_font = get_font(48)
-    small_font = get_font(28)
-    draw.text((410, 70), f"{source_label} DICOM z-axis sequence", font=title_font, fill=(255, 255, 255))
+    angle_font = get_font(56)
+    draw.text((135, 120), "Original: 0 deg", font=title_font, fill=(255, 255, 255))
     draw.text(
-        (410, 1015),
-        f"Slice {slice_index + 1} / {slice_count}",
-        font=small_font,
-        fill=(210, 210, 210),
+        (1055, 120),
+        f"Head extension: {angle:04.1f} deg",
+        font=title_font,
+        fill=(255, 255, 255),
     )
 
     arrow = (255, 210, 60)
     if show_arrow:
-        x0, y0, x1, y1 = 1320, 275, 1450, 205
+        x0, y0, x1, y1 = 1390, 405, 1515, 335
         draw.line((x0, y0, x1, y1), fill=arrow, width=8)
         draw.polygon([(x1, y1), (x1 - 34, y1 + 3), (x1 - 12, y1 + 29)], fill=arrow)
 
-    bar_x, bar_y, bar_w, bar_h = 650, 1018, 870, 12
+    # Minimal progress bar.
+    bar_x, bar_y, bar_w, bar_h = 1040, 980, 760, 12
     draw.rounded_rectangle(
         (bar_x, bar_y, bar_x + bar_w, bar_y + bar_h),
         radius=6,
         fill=(70, 70, 70),
     )
-    fill_w = int(bar_w * (slice_index + 1) / slice_count) if slice_count else 0
+    fill_w = int(bar_w * angle / max_angle) if max_angle else 0
     draw.rounded_rectangle(
         (bar_x, bar_y, bar_x + fill_w, bar_y + bar_h),
         radius=6,
         fill=arrow,
     )
+    draw.text((1040, 1000), "0 deg", font=get_font(24), fill=(210, 210, 210))
+    draw.text((1745, 1000), f"{max_angle:g} deg", font=get_font(24), fill=(210, 210, 210))
 
+    # Invisible-looking spacer: keeps the font imported above alive for some PIL builds.
+    _ = angle_font
     return frame
 
 
 def parse_args():
     parser = argparse.ArgumentParser(
-        description="Generate a z-axis DICOM sequence MP4 video."
+        description="Generate a 0-degree to target-angle head-extension MP4 video."
     )
     parser.add_argument(
         "--input",
@@ -84,7 +140,7 @@ def parse_args():
         "--max-angle",
         type=float,
         default=20.0,
-        help="Kept for compatibility; z-axis sequence videos do not use this value.",
+        help="Target head-extension angle. Default: 20",
     )
     parser.add_argument(
         "--duration",
@@ -97,22 +153,17 @@ def parse_args():
         action="store_true",
         help="Hide the yellow direction arrow.",
     )
-    parser.add_argument(
-        "--source-label",
-        default="DICOM",
-        help="Label shown in the video title.",
-    )
     return parser.parse_args()
 
 
-def generate_video(input_dir, output_path, max_angle=20.0, duration_seconds=6.0, show_arrow=True, source_label="DICOM"):
+def generate_video(input_dir, output_path, max_angle=20.0, duration_seconds=6.0, show_arrow=True):
     output_file = Path(output_path)
     output_file.parent.mkdir(parents=True, exist_ok=True)
 
     volume = load_dicom_volume(input_dir)
-    slice_count = volume.shape[0]
+    before_image = crop_head_neck(sagittal_mip(volume))
 
-    moving_frames = max(1, int(FPS * duration_seconds))
+    moving_frames = int(FPS * duration_seconds)
     hold_frames = FPS * END_HOLD_SECONDS
 
     with imageio.get_writer(
@@ -124,28 +175,19 @@ def generate_video(input_dir, output_path, max_angle=20.0, duration_seconds=6.0,
         macro_block_size=1,
     ) as writer:
         for index in range(moving_frames):
-            t = index / (moving_frames - 1) if moving_frames > 1 else 0
-            slice_index = min(slice_count - 1, int(round(t * (slice_count - 1))))
-            slice_image = Image.fromarray(ct_window(volume[slice_index])).convert("RGB")
-            writer.append_data(np.asarray(make_frame(slice_image, slice_index, slice_count, source_label, show_arrow)))
+            t = index / (moving_frames - 1)
+            angle = max_angle * smoothstep(t)
+            writer.append_data(np.asarray(make_frame(before_image, angle, max_angle, show_arrow)))
 
         for _ in range(hold_frames):
-            slice_image = Image.fromarray(ct_window(volume[-1])).convert("RGB")
-            writer.append_data(np.asarray(make_frame(slice_image, slice_count - 1, slice_count, source_label, show_arrow)))
+            writer.append_data(np.asarray(make_frame(before_image, max_angle, max_angle, show_arrow)))
 
     return output_file.resolve()
 
 
 def main():
     args = parse_args()
-    output_file = generate_video(
-        args.input,
-        args.output,
-        args.max_angle,
-        args.duration,
-        not args.no_arrow,
-        args.source_label,
-    )
+    output_file = generate_video(args.input, args.output, args.max_angle, args.duration, not args.no_arrow)
     print(output_file)
 
 
diff --git a/web_backend.py b/web_backend.py
index 91cb0d6..f5ce435 100644
--- a/web_backend.py
+++ b/web_backend.py
@@ -865,14 +865,13 @@ class Handler(BaseHTTPRequestHandler):
                 max_angle = float(body.get("maxAngle", 20))
                 duration = float(body.get("durationSeconds", 6))
                 show_arrow = bool(body.get("showArrow", True))
-                source_label = body.get("sourceLabel", "DICOM")
 
                 def worker(job_id):
                     job_root = RESULT_DIR / job_id
                     reset_dir(job_root)
                     output_file = job_root / f"head_extension_{job_id}.mp4"
-                    set_job(job_id, message=f"正在生成 {source_label} 的 z 轴序列视频。")
-                    output = generate_video(input_dir, output_file, max_angle, duration, show_arrow, source_label)
+                    set_job(job_id, message="正在生成 0° 到目标角度的视频。")
+                    output = generate_video(input_dir, output_file, max_angle, duration, show_arrow)
                     output = Path(output).resolve()
                     return {
                         "video": {