Broken rope physics

rope_diag.gd

@@ -0,0 +1,78 @@
+extends SceneTree
+
+# Drives the players apart at a set speed and measures actual droop: how much
+# longer the rope's real path is than the straight line between the anchors.
+# droop ~0 means visually taut. That is the thing the fix has to deliver.
+
+var rope
+var p1
+var p2
+var t := 0.0
+var speed := 0.0
+var trial := 0
+var speeds := [1.0, 3.0, 6.0]
+var worst_droop_while_taut := 0.0
+var saw_taut := false
+
+
+func _initialize() -> void:
+	var level = load("res://scenes/game_scene/levels/3dlevel.tscn").instantiate()
+	root.add_child(level)
+	rope = level.get_node("Path3DRope")
+	p1 = level.get_node("Player1")
+	p2 = level.get_node("Player2")
+	rope.can_snap = false
+	speed = speeds[0]
+	print("max_length=%.1f reel_speed=%.1f taut_margin=%.2f" % [
+		rope.max_length, rope.reel_speed, rope.taut_margin])
+
+
+# Length of the rope's actual polyline through every segment.
+func path_len() -> float:
+	var total := 0.0
+	var pts := []
+	for s in rope.segments:
+		var h: float = s.get_child(0).shape.height * 0.5
+		pts.append(s.position + s.transform.basis.y * h)
+	var last = rope.segments[-1]
+	var lh: float = last.get_child(0).shape.height * 0.5
+	pts.append(last.position - last.transform.basis.y * lh)
+	for i in range(pts.size() - 1):
+		total += pts[i].distance_to(pts[i + 1])
+	return total
+
+
+func _physics_process(d: float) -> bool:
+	t += d
+	if t < 0.4:
+		return false
+	# Walk them apart at a controlled rate.
+	p1.global_position.x -= speed * d * 0.5
+	p2.global_position.x += speed * d * 0.5
+	p1.velocity.x = 0.0
+	p2.velocity.x = 0.0
+
+	var gap: float = p1.global_position.distance_to(p2.global_position)
+	var droop: float = path_len() - gap
+	if rope.taut:
+		saw_taut = true
+		worst_droop_while_taut = max(worst_droop_while_taut, droop)
+
+	if fmod(t, 0.6) < d:
+		print("  sep=%.0fm/s gap=%5.2f rope=%5.2f path=%5.2f droop=%5.2f taut=%s" % [
+			speed, gap, rope._rope_length, path_len(), droop, str(rope.taut)])
+
+	if gap > rope.max_length * 1.3:
+		print("trial sep=%.0fm/s -> saw_taut=%s worst droop while taut=%.3f\n" % [
+			speed, str(saw_taut), worst_droop_while_taut])
+		trial += 1
+		if trial >= speeds.size():
+			quit(0)
+			return true
+		speed = speeds[trial]
+		saw_taut = false
+		worst_droop_while_taut = 0.0
+		p1.global_position.x = -1.0
+		p2.global_position.x = 1.0
+		t = 0.0
+	return false