Attempt to call function 'project_ray_origin' in base 'null instance' on a null instance.

nestorac

Hello! I'm new to the forum. I have the following question, I have created a script named 'script.gd' and assigned it to the Camera, I want to develop a RTS game. I need to be able to move a Warrior to where the mouse points to.

The code of script.gd is as follows (taken from Godot Engine Q&A)

extends Node

# Declare member variables here. Examples:
# var a = 2
# var b = "text"


# Called when the node enters the scene tree for the first time.
func _ready():
	pass

func _input(event):
	if (event is InputEventMouseButton and event.pressed and event.button_index == 1):
		var camera = $Camera
		var mouse_pos = get_viewport().get_mouse_position()
		var from = camera.project_ray_origin(mouse_pos)
		var to = from + camera.camera_project_ray_normal(mouse_pos) * camera.distance_from_camera
		# Apply the position to whatever object you want
		get_node("Warrior").global_transform.origin = to

nestorac

Sorry, I get the following error: Attempt to call function 'project_ray_origin' in base 'null instance' on a null instance.

TwistedTwigleg

Welcome to the forums @nestorac!

Does the node this script is attached to have a child Camera node called Camera? The error is saying that the you are trying to call a function called project_ray_origin on a null/non-existent object. This generally occurs when you are using get_node or $ (shorthand for get_node) but the node does not exist in the scene tree or has a different name.

cybereality

That means your camera doesn't exist, or is named something other than "Camera", or is named "Camera" but is not a child on that node the script is on.

nestorac

Thank you! I'm quite busy, I'll take a look tomorrow, it sounds right :-)

nestorac

I have moved the script to the root node, it says:

Invalid call. Nonexistent function 'camera_project_ray_normal' in base 'Camera'.

So, now project_ray_origin works, but camera_project_ray_normal does not work. Thank you!

cybereality

So if you hold Control and click on a function, it will bring up the documentation inside Godot. Check that the function actually exists, that it is named properly and that you are calling it on the correct object.

TwistedTwigleg

You probably need to replace camera_project_ray_normal with the project_ray_normal function :smile:

nestorac

Thank you @TwistedTwigleg , it works :-) I'll try to continue with the game, it's quite challenging. My next step is to be able to move the camera with the mouse and also properly move the warrior. @cybereality , it's really useful to be able to easily read the docs, thank you!