This commit fixes an issue in the tunnel animation where the entire tunnel would shift on each frame.

The new implementation correctly "locks" each concentric ridge of the tunnel to the center point it had at the moment of its creation. This is achieved by storing the center coordinates for each ridge along with its radius and using these per-ridge coordinates for drawing and erasing.

This change creates the intended visual effect of flying through a tunnel with bends, as requested by the user.

Author: google-labs-jules[bot]

gallery/tunnel/tunnel.sh

@@ -30,9 +30,14 @@ animate() {
     width=$(tput cols)
     local height
     height=$(tput lines)
-    local center_x=$((width / 2))
-    local center_y=$((height / 2))
-    local max_radius=$(( (height > width ? height : width) / 2 + 2 ))
+    local original_center_x=$((width / 2))
+    local original_center_y=$((height / 2))
+    local center_x=$original_center_x
+    local center_y=$original_center_y
+    local center_offset_x=$((width / 4))
+    local center_offset_y=$((height / 4))
+    local angle=0
+    local max_radius=$((width + height))
     local ribbon_spacing=7
     local -a radii=()
     local frame_counter=0
@@ -55,39 +60,53 @@ animate() {
     }
 
     while true; do
+        # --- Update center coordinates for a moving tunnel effect (more efficiently) ---
+        read -r angle center_x center_y < <(awk -v angle="$angle" \
+            -v center_x="$original_center_x" -v center_y="$original_center_y" \
+            -v offset_x="$center_offset_x" -v offset_y="$center_offset_y" \
+            'BEGIN {
+                angle += 0.05;
+                cx = int(center_x + offset_x * cos(angle));
+                cy = int(center_y + offset_y * sin(angle));
+                print angle, cx, cy;
+            }')
+
         frame_buffer=""
         # Add a new ribbon every few frames
         if (( frame_counter % ribbon_spacing == 0 )); then
-            radii+=(1)
+            radii+=("1 $center_x $center_y")
         fi
 
         local -a next_radii=()
-        for r in "${radii[@]}"; do
+        for ridge_data in "${radii[@]}"; do
+            local r cx cy
+            read -r r cx cy <<< "$ridge_data"
+
             if [ $r -gt 0 ]; then
                 local prev_r=$((r-1))
                 # Erase the previous shape
                 for ((i=0; i < prev_r; i++)); do
-                    erase_point $((center_x + i)) $((center_y - prev_r + i))
-                    erase_point $((center_x + prev_r - i)) $((center_y + i))
-                    erase_point $((center_x - i)) $((center_y + prev_r - i))
-                    erase_point $((center_x - prev_r + i)) $((center_y - i))
+                    erase_point $((cx + i)) $((cy - prev_r + i))
+                    erase_point $((cx + prev_r - i)) $((cy + i))
+                    erase_point $((cx - i)) $((cy + prev_r - i))
+                    erase_point $((cx - prev_r + i)) $((cy - i))
                 done
             fi
 
             local color=${COLORS[$((r % ${#COLORS[@]}))]}
             local char=${CHARS[$((r % ${#CHARS[@]}))]}
             # Draw a square/diamond shape
             for ((i=0; i < r; i++)); do
-                plot_point $((center_x + i)) $((center_y - r + i)) "$char" "$color"
-                plot_point $((center_x + r - i)) $((center_y + i)) "$char" "$color"
-                plot_point $((center_x - i)) $((center_y + r - i)) "$char" "$color"
-                plot_point $((center_x - r + i)) $((center_y - i)) "$char" "$color"
+                plot_point $((cx + i)) $((cy - r + i)) "$char" "$color"
+                plot_point $((cx + r - i)) $((cy + i)) "$char" "$color"
+                plot_point $((cx - i)) $((cy + r - i)) "$char" "$color"
+                plot_point $((cx - r + i)) $((cy - i)) "$char" "$color"
             done
 
             # Increment radius for the next frame, and keep it if it's not too large
             local next_r=$((r + 1))
             if (( next_r < max_radius )); then
-                next_radii+=($next_r)
+                next_radii+=("$next_r $cx $cy")
             fi
         done