How to add motion trails and afterimages in Godot 4

Motion trails, the fading ghost copies trailing behind a rapid character, enhance game feel without altering physics. This technique, demonstrated for Godot 4, involves snapshots of the character's sprite frame and position every N milliseconds, which fade out over time. A stack of these snapshots creates the trail effect. No shaders or physics are needed to start.

To create motion trails, start by creating a ghost scene with a Sprite2D root, named TrailGhost. The script for TrailGhost reads the source sprite's current frame data, positions itself accordingly, and auto-destroys after fading. The region_rect attribute ensures the snapshot lands on the correct animation frame.

Next, add a Trail child Node2D to the character scene. This node contains the TrailGhost script and references to the character's AnimatedSprite2D (or Sprite2D), along with several export variables to control the trail's behavior: the interval between ghosts, the duration of each ghost, and the start alpha value for the fade effect.

Activate and deactivate the trail emitter (_spawn_ghost() function) around any movement where a trail is desired. A typical dash implementation in the character script would involve activating the trail, applying a tween to the velocity, waiting for the designated duration, then deactivating the trail. For continuous speed-based trails, the activate() and deactivate() functions can be tied to the character's speed instead of manual toggling.