CollisionObject3D文档
Camera3D文档

CollisionObject3D有个信号_input_event，可以用于处理3D拾取。
Camera3D也有project_position用于将屏幕空间坐标投影到3D空间。

extends Node3D#是否处于选中状态
var selected : bool = false
#摄像机的前向量
var front : Vector3 = Vector3(0.0, 0.0, -1.0)
#待拾取的对象
@onready var a : CollisionObject3D = $a
#标记，表示在3D物体上的位置
@onready var mark : MeshInstance3D = $markfunc _on_a_mouse_entered() -> void:print("entered")mark.visible = truefunc _on_a_mouse_exited() -> void:print("exited")mark.visible = falsefunc _on_a_input_event(camera: Node, event: InputEvent, position: Vector3, normal: Vector3, shape_idx: int) -> void:var str = \"camera: " + str(camera) + "\n" + \"event: " + str(event) + "\n" + \"position: " + str(position) + "\n" + \"normal: " + str(normal) + "\n" + \"shape_idx: " + str(shape_idx) + "\n" + \"a.position: " + str(a.position)$mark.position = position$label.text = strif event is InputEventMouseButton:if event.button_index == MOUSE_BUTTON_LEFT:if event.pressed:selected = trueelse:selected = falseelif event is InputEventMouseMotion:if selected:var c : Camera3D = camera as Camera3D#由相机指向物体的向量var dir : Vector3 = a.position - c.position#dir投影到front上所得的长度var dis : float = front.dot(dir)#将位置投影到3D空间a.position = c.project_position(event.position, dis)