Several actions in Godot are triggered by callbacks or virtual functions, so there is no need to write code that runs all the time.
However, it is still common to need a script to be processed on every frame. There are two types of processing: idle processing and physics processing.
Idle processing is activated when the method Node._process() is found in a script. It can be turned off and on with the Node.set_process() function.
This method will be called every time a frame is drawn:
It’s important to bear in mind that the frequency with which
will be called depends on how many frames per second (FPS) your application
is running at. This rate can vary over time and devices.
To help manage this variability the
delta parameter contains the time
elapsed in seconds, as a floating point, since the previous call to
This parameter can be used to make sure things always take the same amount of time, regardless of the game’s FPS.
For example, movement is often multiplied with a time delta to make movement speed both constant and independent from the frame rate.
Physics processing with
_physics_process() is similar, but it should be used for processes that
must happen before each physics step, such as controlling a character.
It always runs before a physics step and it is called at fixed time intervals:
60 times per second by default. You can change the interval from the Project Settings, under
Physics -> Common -> Physics Fps.
_process(), however, is not synced with physics. Its frame rate is not constant and is dependent
on hardware and game optimization. Its execution is done after the physics step on single-threaded games.
A simple way to see the
_process() function at work is to create a scene with a single Label node,
with the following script:
Which will show a counter increasing each frame.
Groups in Godot work like tags you might have come across in other software. A node can be added to as many groups as desired. This is a useful feature for organizing large scenes. There are two ways to add nodes to groups. The first is from the UI, using the Groups button under the Node panel:
And the second way is from code. The following script would add the current
node to the
enemies group as soon as it appeared in the scene tree.
This way, if the player is discovered sneaking into a secret base, all enemies can be notified about its alarm sounding by using SceneTree.call_group():
The above code calls the function
player_was_discovered on every
member of the group
It is also possible to get the full list of
enemies nodes by
The SceneTree class provides many useful methods, like interacting with scenes, their node hierarchy and groups of nodes. It allows you to easily switch scenes or reload them, to quit the game or pause and unpause it. It even comes with interesting signals. So check it out if you have some time!
Godot has a system of notifications. These are usually not needed for scripting, as it’s too low-level and virtual functions are provided for most of them. It’s just good to know they exist. For example, you may add an Object._notification() function in your script:
The documentation of each class in the Class Reference shows the notifications it can receive. However, in most cases GDScript provides simpler overridable functions.
Such overridable functions, which are described as follows, can be applied to nodes:
As mentioned before, it’s better to use these functions instead of the notification system.
To create a node from code, call the
.new() method, like for any
other class-based datatype. For example:
To delete a node, be it inside or outside the scene,
free() must be
When a node is freed, it also frees all its child nodes. Because of this, manually deleting nodes is much simpler than it appears. Free the base node and everything else in the subtree goes away with it.
A situation might occur where we want to delete a node that is currently «blocked», because it is emitting a signal or calling a function. This will crash the game. Running Godot with the debugger will often catch this case and warn you about it.
The safest way to delete a node is by using Node.queue_free(). This erases the node safely during idle.
Instancing a scene from code is done in two steps. The first one is to load the scene from your hard drive:
Preloading it can be more convenient, as it happens at parse time (GDScript only):
scene is not yet a node. It’s packed in a
special resource called PackedScene.
To create the actual node, the function
must be called. This will return the tree of nodes that can be added to
the active scene:
The advantage of this two-step process is that a packed scene may be kept loaded and ready to use so that you can create as many instances as desired. This is especially useful to quickly instance several enemies, bullets, and other entities in the active scene.
Register scripts as classes¶
Godot has a «Script Class» feature to register individual scripts with the Editor. By default, you can only access unnamed scripts by loading the file directly.
You can name a script and register it as a type in the editor with the
class_name keyword followed by the class’s name. You may add a comma and an
optional path to an image to use as an icon. You will then find your new type in
the Node or Resource creation dialog.
In Godot 3.1:
- Only GDScript and NativeScript, i.e., C++ and other GDNative-powered languages, can register scripts.
- Only GDScript creates global variables for each named script.