Enhance ball rings with neon glow effect (additive blending)

app.py

@@ -794,10 +794,10 @@ FX_GLOW_COLOR = np.array([1.0, 0.1, 0.6], dtype=np.float32)
 FX_EPS = 1e-6
 GHOST_TRAIL_COLOR = np.array([1.0, 0.0, 1.0], dtype=np.float32)
 GHOST_TRAIL_ALPHA = 0.55
-BALL_RING_ALPHA = 0.85
-BALL_RING_THICKNESS_PX = 4
-BALL_RING_FEATHER_SIGMA = 0.75
-BALL_RING_INTENSITY_GAMMA = 0.65
+BALL_RING_ALPHA = 1.5
+BALL_RING_THICKNESS_PX = 3
+BALL_RING_FEATHER_SIGMA = 1.5
+BALL_RING_INTENSITY_GAMMA = 1.0
 
 
 def _maybe_upscale_for_display(image: Image.Image) -> Image.Image:
@@ -980,8 +980,14 @@ def compose_frame(state: AppState, frame_idx: int, remove_bg: bool = False) -> I
             ring_np = ring_np * np.clip(1.0 - current_union_mask, 0.0, 1.0)
         if ring_np.max() > FX_EPS:
             base_np = np.array(out_img).astype(np.float32) / 255.0
-            ring_alpha = ring_np[..., None] * BALL_RING_ALPHA
-            base_np = (1.0 - ring_alpha) * base_np + ring_alpha * GHOST_TRAIL_COLOR
+            # Additive blending (Linear Dodge) for neon effect
+            # ring_np has the intensity profile (0.0 to 1.0)
+            glow_factor = ring_np[..., None] * BALL_RING_ALPHA
+            added_light = glow_factor * GHOST_TRAIL_COLOR
+            
+            # Add light to background, clipping at white
+            base_np = np.clip(base_np + added_light, 0.0, 1.0)
+
             if focus_mask is not None:
                 focus_alpha = np.clip(focus_mask, 0.0, 1.0)[..., None]
                 orig_np = np.array(frame).astype(np.float32) / 255.0
@@ -1232,12 +1238,24 @@ def _build_ball_ring_mask(state: AppState, frame_idx: int) -> np.ndarray | None:
             continue
         center = (int(round(cx)), int(round(cy)))
         radius_int = max(1, int(round(radius)))
-        thickness = max(1, int(round(BALL_RING_THICKNESS_PX)))
-        cv2.circle(ring_mask, center, radius_int, 1.0, thickness=thickness)
+        
+        # Multi-pass drawing for neon effect: Glow -> Mid -> Core
+        # 1. Outer Glow
+        t_glow = max(1, int(round(BALL_RING_THICKNESS_PX * 4.0)))
+        cv2.circle(ring_mask, center, radius_int, 0.3, thickness=t_glow)
+        
+        # 2. Inner Glow
+        t_mid = max(1, int(round(BALL_RING_THICKNESS_PX * 2.0)))
+        cv2.circle(ring_mask, center, radius_int, 0.6, thickness=t_mid)
+
+        # 3. Core (Sharp)
+        t_core = max(1, int(round(BALL_RING_THICKNESS_PX)))
+        cv2.circle(ring_mask, center, radius_int, 1.0, thickness=t_core)
 
     if ring_mask is None or ring_mask.max() <= FX_EPS:
         return None
 
+    # Soft blur to blend the stepped layers into a smooth gradient
     ring_mask = cv2.GaussianBlur(ring_mask, (0, 0), sigmaX=BALL_RING_FEATHER_SIGMA, sigmaY=BALL_RING_FEATHER_SIGMA)
     max_val = float(ring_mask.max())
     if max_val > FX_EPS: