Cast Ray3D straight away from a moving camera

[regnarok]

Godot Version

4.3

Question

So, I have a large cube that my camera rotates around. I want to cast a ray from the mouse position on the screen and straight away from camera. I can get the mouse position, but I dont know how to get the direction to cast the ray.

There maybe a better way to do this. Why I want this is because I want the player to be able to place objects on the cube. I want the objects to be selected and then follow the mouse around along the surface of the cube until the player places them. However, I don’t know how to get the location on the cube relative to mouse position projected from camera in order to place/move the object.

[herrspaten]

The following is my implementation:

func get_collider_data() -> Dictionary:
	var mouse_pos: Vector2 = viewport.get_mouse_position()
	_ray_query_parameters.from = camera.camera.project_ray_origin(mouse_pos)
	_ray_query_parameters.to = _ray_query_parameters.from + camera.camera.project_ray_normal(mouse_pos) * MAX_RAY_LENGTH
	
	return direct_space_state.intersect_ray(_ray_query_parameters)

The direct_space_state is the following:

var direct_space_state: PhysicsDirectSpaceState3D = camera.get_world_3d().direct_space_state

and the ray_query_parameters are “PhysicsRayQueryParameters3D”

[regnarok]

Thanks, I used what you had as a base, and instead of using the actual built in ray from the camera I used its methods in combination with the RayCastNode.

Here is the code I ended up doing if you are curious.

func _physics_process(_delta: float) -> void:
	if follow_mouse:
		var mouse_pos : Vector2 = get_viewport().get_mouse_position()
		var from : Vector3 = camera.project_ray_origin(mouse_pos)
		var to : Vector3 = from + camera.project_ray_normal(mouse_pos) * RAY_LENGTH
		ray.position = from
		ray.set_target_position(to)
		ray.force_raycast_update()
		var set_pos : Vector3 = snapped(ray.get_collision_point(),Vector3(2,2,2))
		if abs(set_pos.x) == 10:
			if set_pos.x == 10:
				current_item.position = set_pos + Vector3(1,0,0)
			else:
				current_item.position = set_pos - Vector3(1,0,0)
		elif abs(set_pos.y) == 10:
			if set_pos.y == 10:
				current_item.position = set_pos + Vector3(0,1,0)
			else:
				current_item.position = set_pos - Vector3(0,1,0)
		else:
			if set_pos.z == 10:
				current_item.position = set_pos + Vector3(0,0,1)
			else:
				current_item.position = set_pos - Vector3(0,0,1)