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Expand Up @@ -4,7 +4,7 @@ Scene organization
==================

This article covers topics related to the effective organization of
scene content. Which nodes should one use? Where should one place them?
scene content. Which nodes should you use? Where should you place them?
How should they interact?

How to build relationships effectively
Expand All @@ -21,10 +21,9 @@ possible. Re-using the scene in multiple places creates issues because the
node paths do not find their targets and signal connections established in the
editor break.

To fix these problems, one must instantiate the sub-scenes without them
requiring details about their environment. One needs to be able to trust
that the sub-scene will create itself without being picky about how one uses
it.
To fix these problems, you must instantiate the sub-scenes without them
requiring details about their environment. You need to be able to trust
that the sub-scene will create itself without being picky about how it's used.

One of the biggest things to consider in OOP is maintaining
focused, singular-purpose classes with
Expand All @@ -35,8 +34,8 @@ maintainability) and improves their reusability.
These OOP best practices have *several* implications for best practices
in scene structure and script usage.

**If at all possible, one should design scenes to have no dependencies.**
That is, one should create scenes that keep everything they need within
**If at all possible, you should design scenes to have no dependencies.**
That is, you should create scenes that keep everything they need within
themselves.

If a scene must interact with an external context, experienced developers
Expand All @@ -46,7 +45,7 @@ This technique involves having a high-level API provide the dependencies of the
low-level API. Why do this? Because classes which rely on their external
environment can inadvertently trigger bugs and unexpected behavior.

To do this, one must expose data and then rely on a parent context to
To do this, you must expose data and then rely on a parent context to
initialize it:

1. Connect to a signal. Extremely safe, but should be used only to "respond" to
Expand Down Expand Up @@ -148,14 +147,14 @@ initialize it:
GetNode(TargetPath); // Use parent-defined NodePath.

These options hide the points of access from the child node. This in turn
keeps the child **loosely coupled** to its environment. One can reuse it
keeps the child **loosely coupled** to its environment. You can reuse it
in another context without any extra changes to its API.

.. note::

Although the examples above illustrate parent-child relationships,
the same principles apply towards all object relations. Nodes which
are siblings should only be aware of their hierarchies while an ancestor
are siblings should only be aware of their own hierarchies while an ancestor
mediates their communications and references.

.. tabs::
Expand Down Expand Up @@ -201,21 +200,21 @@ in another context without any extra changes to its API.
}

The same principles also apply to non-Node objects that maintain dependencies
on other objects. Whichever object actually owns the objects should manage
on other objects. Whichever object owns the other objects should manage
the relationships between them.

.. warning::

One should favor keeping data in-house (internal to a scene) though as
You should favor keeping data in-house (internal to a scene), though, as
placing a dependency on an external context, even a loosely coupled one,
still means that the node will expect something in its environment to be
true. The project's design philosophies should prevent this from happening.
If not, the code's inherent liabilities will force developers to use
documentation to keep track of object relations on a microscopic scale; this
is otherwise known as development hell. Writing code that relies on external
documentation for one to use it safely is error-prone by default.
documentation to use it safely is error-prone by default.

To avoid creating and maintaining such documentation, one converts the
To avoid creating and maintaining such documentation, you convert the
dependent node ("child" above) into a tool script that implements
``_get_configuration_warnings()``.
Returning a non-empty PackedStringArray from it will make the Scene dock generate a
Expand All @@ -234,7 +233,7 @@ in another context without any extra changes to its API.
So, why does all this complex switcheroo work? Well, because scenes operate
best when they operate alone. If unable to work alone, then working with
others anonymously (with minimal hard dependencies, i.e. loose coupling)
is the next best thing. Inevitably, changes may need to be made to a class and
is the next best thing. Inevitably, changes may need to be made to a class, and
if these changes cause it to interact with other scenes in unforeseen ways,
then things will start to break down. The whole point of all this indirection
is to avoid ending up in a situation where changing one class results in
Expand All @@ -251,44 +250,43 @@ by *all* OOP principles. Examples include...
Choosing a node tree structure
------------------------------

So, a developer starts work on a game only to stop at the vast possibilities
before them. They might know what they want to do, what systems they want to
have, but *where* to put them all? Well, how one goes about making their game
is always up to them. One can construct node trees in countless ways.
But, for those who are unsure, this helpful guide can give them a sample of
a decent structure to start with.
You might start to work on a game but get overwhelmed by the vast possibilities
before you. You might know what you want to do, what systems you want to
have, but *where* do you put them all? How you go about making your game
is always up to you. You can construct node trees in countless ways.
If you are unsure, this guide can give you a sample of a decent structure to
start with.

A game should always have a sort of "entry point"; somewhere the developer can
definitively track where things begin so that they can follow the logic as it
continues elsewhere. This place also serves as a bird's eye view of all of the
other data and logic in the program. For traditional applications, this would
be the "main" function. In this case, it would be a Main node.
A game should always have an "entry point"; somewhere you can definitively
track where things begin so that you can follow the logic as it continues
elsewhere. It also serves as a bird's eye view of all other data and logic
in the program. For traditional applications, this is normally a "main"
function. In Godot, it's a Main node.

- Node "Main" (main.gd)

The ``main.gd`` script would then serve as the primary controller of one's
game.
The ``main.gd`` script will serve as the primary controller of your game.

Then one has their actual in-game "World" (a 2D or 3D one). This can be a child
of Main. In addition, one will need a primary GUI for their game that manages
Then you have an in-game "World" (a 2D or 3D one). This can be a child
of Main. In addition, you will need a primary GUI for your game that manages
the various menus and widgets the project needs.

- Node "Main" (main.gd)
- Node2D/Node3D "World" (game_world.gd)
- Control "GUI" (gui.gd)

When changing levels, one can then swap out the children of the "World" node.
:ref:`Changing scenes manually <doc_change_scenes_manually>` gives users full
control over how their game world transitions.
When changing levels, you can then swap out the children of the "World" node.
:ref:`Changing scenes manually <doc_change_scenes_manually>` gives you full
control over how your game world transitions.

The next step is to consider what gameplay systems one's project requires.
If one has a system that...
The next step is to consider what gameplay systems your project requires.
If you have a system that...

1. tracks all of its data internally
2. should be globally accessible
3. should exist in isolation

... then one should create an :ref:`autoload 'singleton' node <doc_singletons_autoload>`.
... then you should create an :ref:`autoload 'singleton' node <doc_singletons_autoload>`.

.. note::

Expand All @@ -298,78 +296,76 @@ If one has a system that...
to swap out the main scene's content. This structure more or less keeps
the "World" as the main game node.

Any GUI would need to also be a
singleton; be a transitory part of the "World"; or be manually added as a
direct child of the root. Otherwise, the GUI nodes would also delete
themselves during scene transitions.
Any GUI would also need to be either a singleton, a transitory part of the
"World", or manually added as a direct child of the root. Otherwise, the
GUI nodes would also delete themselves during scene transitions.

If one has systems that modify other systems' data, one should define those as
their own scripts or scenes rather than autoloads. For more information on the
reasons, please see the
:ref:`Autoloads versus regular nodes <doc_autoloads_versus_internal_nodes>`
documentation.
If you have systems that modify other systems' data, you should define those as
their own scripts or scenes, rather than autoloads. For more information, see
:ref:`Autoloads versus regular nodes <doc_autoloads_versus_internal_nodes>`.

Each subsystem within one's game should have its own section within the
SceneTree. One should use parent-child relationships only in cases where nodes
Each subsystem within your game should have its own section within the
SceneTree. You should use parent-child relationships only in cases where nodes
are effectively elements of their parents. Does removing the parent reasonably
mean that one should also remove the children? If not, then it should have its
mean that the children should also be removed? If not, then it should have its
own place in the hierarchy as a sibling or some other relation.

.. note::

In some cases, one needs these separated nodes to *also* position themselves
relative to each other. One can use the
In some cases, you need these separated nodes to *also* position themselves
relative to each other. You can use the
:ref:`RemoteTransform <class_RemoteTransform3D>` /
:ref:`RemoteTransform2D <class_RemoteTransform2D>` nodes for this purpose.
They will allow a target node to conditionally inherit selected transform
elements from the Remote\* node. To assign the ``target``
:ref:`NodePath <class_NodePath>`, use one of the following:

1. A reliable third party, likely a parent node, to mediate the assignment.
2. A group, to easily pull a reference to the desired node (assuming there
2. A group, to pull a reference to the desired node (assuming there
will only ever be one of the targets).

When should one do this? Well, this is subjective. The dilemma arises when
one must micro-manage when a node must move around the SceneTree to preserve
When you should do this is subjective. The dilemma arises when you must
micro-manage when a node must move around the SceneTree to preserve
itself. For example...

- Add a "player" node to a "room".
- Need to change rooms, so one must delete the current room.
- Before the room can be deleted, one must preserve and/or move the player.
- Need to change rooms, so you must delete the current room.
- Before the room can be deleted, you must preserve and/or move the player.

Is memory a concern?
If memory is not a concern, you can...

- If not, one can just create the two rooms, move the player
and delete the old one. No problem.
- Create the new room.
- Move the player to the new room.
- Delete the old room.

If so, one will need to...
If memory is a concern, instead you will need to...

- Move the player somewhere else in the tree.
- Delete the room.
- Instantiate and add the new room.
- Re-add the player.
- Re-add the player to the new room.

The issue is that the player here is a "special case"; one where the
The issue is that the player here is a "special case" where the
developers must *know* that they need to handle the player this way for the
project. As such, the only way to reliably share this information as a team
is to *document* it. Keeping implementation details in documentation however
is dangerous. It's a maintenance burden, strains code readability, and bloats
the intellectual content of a project unnecessarily.
project. The only way to reliably share this information as a team
is to *document* it. Keeping implementation details in documentation is
dangerous. It's a maintenance burden, strains code readability, and
unnecessarily bloats the intellectual content of a project.

In a more complex game with larger assets, it can be a better idea to simply
keep the player somewhere else in the SceneTree entirely. This results in:
In a more complex game with larger assets, it can be a better idea to keep
the player somewhere else in the SceneTree entirely. This results in:

1. More consistency.
2. No "special cases" that must be documented and maintained somewhere.
3. No opportunity for errors to occur because these details are not accounted
for.

In contrast, if one ever needs to have a child node that does *not* inherit
the transform of their parent, one has the following options:
In contrast, if you ever need a child node that does *not* inherit
the transform of its parent, you have the following options:

1. The **declarative** solution: place a :ref:`Node <class_Node>` in between
them. As nodes with no transform, Nodes will not pass along such
information to their children.
them. Since it doesn't have a transform, they won't pass this information
to its children.
2. The **imperative** solution: Use the ``top_level`` property for the
:ref:`CanvasItem <class_CanvasItem_property_top_level>` or
:ref:`Node3D <class_Node3D_property_top_level>` node. This will make
Expand All @@ -380,9 +376,9 @@ own place in the hierarchy as a sibling or some other relation.
If building a networked game, keep in mind which nodes and gameplay systems
are relevant to all players versus those just pertinent to the authoritative
server. For example, users do not all need to have a copy of every players'
"PlayerController" logic. Instead, they need only their own. As such, keeping
these in a separate branch from the "world" can help simplify the management
of game connections and the like.
"PlayerController" logic - they only need their own. Keeping them in a
separate branch from the "world" can help simplify the management of game
connections and the like.

The key to scene organization is to consider the SceneTree in relational terms
rather than spatial terms. Are the nodes dependent on their parent's existence?
Expand All @@ -392,5 +388,5 @@ that parent (and likely part of that parent's scene if they aren't already).

Does this mean nodes themselves are components? Not at all.
Godot's node trees form an aggregation relationship, not one of composition.
But while one still has the flexibility to move nodes around, it is still best
But while you still have the flexibility to move nodes around, it is still best
when such moves are unnecessary by default.

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