🎨 Cleanup projectile trails logic

entities/weapons/space_gun/projectile.tscn

@@ -23,11 +23,10 @@ radius = 0.15
 script = ExtResource("1_4j1dp")
 EXPLOSION = ExtResource("2_llml6")
 
-[node name="Trail3D" type="MeshInstance3D" parent="."]
+[node name="ProjectileTrail" type="MeshInstance3D" parent="."]
 material_override = SubResource("StandardMaterial3D_4a265")
 script = ExtResource("3_ygqbh")
-_from_width = 0.15
-_scale_acceleration = 0.5
+_start_width = 0.15
 _lifespan = 0.25
 _start_color = Color(0, 0.498039, 0.854902, 1)
 _end_color = Color(1, 1, 1, 0)

entities/weapons/space_gun/projectile_trail.gd

@@ -14,16 +14,12 @@
 # along with this program.  If not, see <https://www.gnu.org/licenses/>.
 class_name Trail3D extends MeshInstance3D
 
-var _points : Array = [] # 3D points of trail
-var _widths : Array = [] # Calculated widths of trail
-var _lifespans : Array = [] # Trail point lifespans
+@export var _trail_enabled : bool = true
 
-@export var _trail_enabled : bool = true # Is trail shown?
+@export var _start_width : float = 0.5
+@export var _end_width : float = 0.0
 
-@export var _from_width : float = 0.5 # Starting width
-@export var _to_width : float = 0.0 # Ending width
-
-@export_range(0.5, 1.5) var _scale_acceleration : float = 1.0 # Scaling speed
+@export_range(0.5, 1.5) var _scaling_acceleration : float = 0.5
 
 @export var _motion_delta : float = 0.1 # Smoothness of trail
 @export var _lifespan : float = 1.0 # Duration of trail
@@ -31,64 +27,70 @@ var _lifespans : Array = [] # Trail point lifespans
 @export var _start_color : Color = Color(1.0, 1.0, 1.0, 1.0) # Start color
 @export var _end_color : Color = Color(1.0, 1.0, 1.0, 1.0) # End color
 
-var _old_pos : Vector3 # Previous pos
+var _previous_position : Vector3
+var _points : Array
+
+class PointData:
+	var position : Vector3
+	var width_0 : Vector3
+	var width_1 : Vector3
+	var lifespan : float = 0.0
 
 func _append_point() -> void:
-	_points.append(get_global_transform().origin)
-	_widths.append([
-		get_global_transform().basis.x * _from_width,
-		get_global_transform().basis.x * _from_width - get_global_transform().basis.x * _to_width
-	])
-	_lifespans.append(0.0)
+	var point_data : PointData = PointData.new()
+	point_data.position = global_position
+	point_data.width_0 = global_basis.x * _start_width
+	point_data.width_1 = global_basis.x * _start_width - global_basis.x * _end_width
 
-func _remove_point(i : int) -> void:
-	_points.remove_at(i)
-	_widths.remove_at(i)
-	_lifespans.remove_at(i)
+	_points.append(point_data)
 
 func _ready() -> void:
-	_old_pos = get_global_transform().origin
+	_previous_position = global_position
 	mesh = ImmediateMesh.new()
 
 func _process(delta : float) -> void:
-	if(_old_pos - get_global_transform().origin).length() > _motion_delta and _trail_enabled:
-		_append_point() # Create new point
-		_old_pos = get_global_transform().origin # Update previous position to current position coordinates
+	if(_previous_position - global_position).length() > _motion_delta and _trail_enabled:
+		_append_point()
+		_previous_position = global_position
 
-	# Update the lifespan
-	var p : int = 0
-	var max_points : int = _points.size()
-	while p < max_points:
-		_lifespans[p] += delta
-		if _lifespans[p] > _lifespan:
-			_remove_point(p)
-			p -= 1
-			if (p < 0): p = 0
+	_update_lifespans(delta)
+	_render_trail()
 
-		max_points = _points.size()
-		p += 1
+# Update all lifespans and use a mark-and-sweep algorithm to remove "expired" points
+func _update_lifespans(delta : float) -> void:
+	var points_to_remove : Array = []
+	for point_data : PointData in _points:
+		point_data.lifespan += delta
+		if point_data.lifespan > _lifespan:
+			points_to_remove.append(point_data)
 
+	for point_data : PointData in points_to_remove:
+		_points.erase(point_data)
+
+func _render_trail() -> void:
 	mesh.clear_surfaces()
 
-	# If less than 2 points, stop rendering trail
-	if _points.size() < 2:
+	var number_of_points : int = _points.size()
+	if number_of_points < 2:
 		return
 
-	# Render new mesh for each point
+	# Render new mesh for each point, triangle strips draw 2 triangles each 4 points
+	# which is perfect for a trail
 	mesh.surface_begin(Mesh.PRIMITIVE_TRIANGLE_STRIP)
 
-	for i in range(_points.size()):
-		var t : float = float(i) / (_points.size() - 1.0)
-		var curr_color : Color = _start_color.lerp(_end_color, 1 - t)
-		mesh.surface_set_color(curr_color)
+	for point_index in range(number_of_points):
+		var point_data : PointData = _points[point_index]
+		var t : float = float(point_index) / (number_of_points - 1.0)
+		var current_color : Color = _start_color.lerp(_end_color, 1 - t)
+		mesh.surface_set_color(current_color)
 
-		var curr_width : Vector3 = _widths[i][0] - pow(1 - t, _scale_acceleration) * _widths[i][1]
+		var current_width : Vector3 = point_data.width_0 - pow(1 - t, _scaling_acceleration) * point_data.width_1
 
-		var t0 : float = i / _points.size()
+		var t0 : float = float(point_index) / float(number_of_points)
 		var t1 : float = t
 
 		mesh.surface_set_uv(Vector2(t0, 0))
-		mesh.surface_add_vertex(to_local(_points[i] + curr_width))
+		mesh.surface_add_vertex(to_local(point_data.position + current_width))
 		mesh.surface_set_uv(Vector2(t1, 1))
-		mesh.surface_add_vertex(to_local(_points[i] - curr_width))
+		mesh.surface_add_vertex(to_local(point_data.position - current_width))
 	mesh.surface_end()