Feather ball mask for live and ghost overlays

app.py

@@ -924,6 +924,14 @@ def compose_frame(state: AppState, frame_idx: int, remove_bg: bool = False) -> I
             combined_mask = current_union_mask
             if combined_mask is None:
                 combined_mask = np.zeros((frame_np.shape[0], frame_np.shape[1]), dtype=np.float32)
+            # Apply falloff to ball component when rendering foreground
+            if BALL_OBJECT_ID in masks:
+                ball_mask = masks[BALL_OBJECT_ID]
+                if ball_mask is not None:
+                    combined_mask = np.maximum(
+                        combined_mask,
+                        _apply_radial_falloff(np.clip(ball_mask.astype(np.float32), 0.0, 1.0)),
+                    )
             result_np = _apply_cutout_fx(state, frame_np, combined_mask)
             out_img = Image.fromarray(result_np)
         else:
@@ -932,6 +940,17 @@ def compose_frame(state: AppState, frame_idx: int, remove_bg: bool = False) -> I
                 overlay_masks = {oid: mask for oid, mask in masks.items() if oid != BALL_OBJECT_ID}
             if overlay_masks:
                 out_img = overlay_masks_on_frame(out_img, overlay_masks, state.color_by_obj, alpha=0.65)
+            # Overlay feathered ball on top
+            if BALL_OBJECT_ID in masks:
+                ball_mask = masks[BALL_OBJECT_ID]
+                if ball_mask is not None:
+                    ball_alpha = _apply_radial_falloff(ball_mask)
+                    if ball_alpha is not None and ball_alpha.max() > FX_EPS:
+                        base_np = np.array(out_img).astype(np.float32) / 255.0
+                        color = np.array(state.color_by_obj.get(BALL_OBJECT_ID, (255, 255, 0)), dtype=np.float32) / 255.0
+                        alpha = np.clip(ball_alpha[..., None], 0.0, 1.0)
+                        base_np = (1.0 - alpha) * base_np + alpha * color
+                        out_img = Image.fromarray(np.clip(base_np * 255.0, 0, 255).astype(np.uint8))
 
     if ghost_mask is not None:
         ghost_np = np.clip(ghost_mask.astype(np.float32), 0.0, 1.0)
@@ -1118,6 +1137,7 @@ def _build_ball_trail_mask(state: AppState, frame_idx: int) -> np.ndarray | None
         if mask_np.ndim == 3:
             mask_np = mask_np.squeeze()
         mask_np = np.clip(mask_np, 0.0, 1.0)
+        mask_np = _apply_radial_falloff(mask_np)
         if trail_mask is None:
             trail_mask = np.zeros_like(mask_np, dtype=np.float32)
         if trail_mask.shape != mask_np.shape:
@@ -1149,6 +1169,31 @@ def _compute_mask_centroid(mask: np.ndarray) -> tuple[int, int] | None:
     return cx, cy
 
 
+def _apply_radial_falloff(mask: np.ndarray, strength: float = 1.5) -> np.ndarray:
+    if mask is None:
+        return None
+    mask_np = np.clip(mask.astype(np.float32), 0.0, 1.0)
+    if mask_np.ndim == 3:
+        mask_np = mask_np.squeeze()
+    if mask_np.max() <= FX_EPS:
+        return mask_np
+
+    centroid = _compute_mask_centroid(mask_np)
+    if centroid is None:
+        return mask_np
+    cx, cy = centroid
+
+    h, w = mask_np.shape
+    yy, xx = np.ogrid[:h, :w]
+    dist = np.sqrt((xx - cx) ** 2 + (yy - cy) ** 2)
+    max_dist = dist[mask_np > FX_EPS].max() if np.any(mask_np > FX_EPS) else 0.0
+    if max_dist <= FX_EPS:
+        return mask_np
+    falloff = 1.0 - np.clip(dist / max_dist, 0.0, 1.0)
+    falloff = np.power(falloff, strength)
+    return np.clip(mask_np * falloff, 0.0, 1.0)
+
+
 def _update_centroids_for_frame(state: AppState, frame_idx: int):
     if state is None:
         return