サーバーを使用した最適化

Engines like Godot provide increased ease of use thanks to their high-level constructs and features. Most of them are accessed and used via the scene system. Using nodes and resources simplifies project organization and asset management in complex games.

There are several drawbacks to this:

  • 複雑さがさらに増します。

  • 単純な API を直接使用するよりもパフォーマンスが低下します。

  • It is not possible to use multiple threads to control them.

  • より多くのメモリが必要になります。

In most cases, this is not really a problem. Godot is well-optimized, and most operations are handled with signals, which means no polling is required. Still, sometimes, we want to extract better performance from the hardware when other avenues of optimization have been exhausted. For example, dealing with tens of thousands of instances for something that needs to be processed every frame can be a bottleneck.

このような状況では、プログラマはゲームエンジンを使用していることを後悔し、より手作りな低レベルのゲームコード実装に戻りたいと思うようになります。

それでも、Godotはこの問題を回避するように設計されています。

参考

You can see how using low-level servers works in action using the Bullet Shower demo project.

サーバー

One of the most interesting design decisions for Godot is the fact that the whole scene system is optional. While it is not possible to compile it out, it can be completely bypassed.

At the core, Godot uses the concept of Servers. They are low-level APIs to control rendering, physics, sound, etc. The scene system is built on top of them and uses them directly. The most common servers are:

Explore their APIs, and you will realize that all the functions provided are low-level implementations of everything Godot allows you to do using nodes.

RIDs

サーバーを使用する鍵は、リソースID(RID)オブジェクトを理解することです。これらは、サーバー実装への不透明なハンドルです。それらは手動で割り当てられ、解放されます。サーバーのほぼすべての機能には、実際のリソースにアクセスするためのRIDが必要です。

ほとんどの Godot ノードとリソースには、サーバーからのこれらの RID が内部的に含まれており、さまざまな関数を使用して取得できます。実際、Resource を継承するものはすべて、RID に直接キャストでき、サーバー API に渡すことができます。ただし、すべてのリソースに RID が含まれているわけではありません。その場合 RID は空になります。

警告

Resources are reference-counted (see RefCounted), and references to a resource's RID are not counted when determining whether the resource is still in use. Make sure to keep a reference to the resource outside the server. Otherwise, both the resource and its RID will be erased.

ノードには、次の多くの機能が用意されています:

  • CanvasItemの場合、CanvasItem.get_canvas_item() メソッドは、サーバー内のキャンバスアイテムRIDを返します。

  • CanvasLayerの場合、CanvasLayer.get_canvas() メソッドはサーバーのキャンバスRIDを返します。

  • ビューポートの場合、Viewport.get_viewport_rid() メソッドはサーバーのビューポートRIDを返します。

  • For 2D, the World2D resource (obtainable in the Viewport and CanvasItem nodes) contains functions to get the RenderingServer Canvas, and the PhysicsServer2D Space. This allows creating 2D objects directly with the server API and using them.

  • For 3D, the World3D resource (obtainable in the Viewport and Node3D nodes) contains functions to get the RenderingServer Scenario, and the PhysicsServer Space. This allows creating 3D objects directly with the server API and using them.

  • The VisualInstance3D class, allows getting the scenario instance and instance base via the VisualInstance3D.get_instance() and VisualInstance3D.get_base() respectively.

使い慣れたノードとリソースを調べて、サーバーの RID を取得する関数を見つけてください。

すでにノードが関連付けられているオブジェクトからRIDを制御することはお勧めしません。代わりに、サーバー関数を常に使用して、新しい関数を作成および制御し、既存の関数と対話する必要があります。

スプライトの作成

This is an example of how to create a sprite from code and move it using the low-level CanvasItem API.

注釈

When creating canvas items using the RenderingServer, you should reset physics interpolation on the first frame using RenderingServer.canvas_item_reset_physics_interpolation(). This ensures proper synchronization between the rendering and physics systems.

If this is not done, the canvas item may appear to teleport in when the scene is loaded, rather than appearing directly at its intended location.

extends Node2D


# RenderingServer expects references to be kept around.
var texture


func _ready():
    # Create a canvas item, child of this node.
    var ci_rid = RenderingServer.canvas_item_create()
    # Make this node the parent.
    RenderingServer.canvas_item_set_parent(ci_rid, get_canvas_item())
    # Draw a texture on it.
    # Remember to keep this reference.
    texture = load("res://my_texture.png")
    # Add it, centered.
    RenderingServer.canvas_item_add_texture_rect(ci_rid, Rect2(-texture.get_size() / 2, texture.get_size()), texture)
    # Add the item, rotated 45 degrees and translated.
    var xform = Transform2D().rotated(deg_to_rad(45)).translated(Vector2(20, 30))
    RenderingServer.canvas_item_set_transform(ci_rid, xform)
    # Reset physics interpolation for this item.
    RenderingServer.canvas_item_reset_physics_interpolation(ci_rid)

The Canvas Item API in the server allows you to add draw primitives to it. Once added, they can't be modified. The Item needs to be cleared and the primitives re-added. This is not the case for setting the transform, which can be done as many times as desired.

プリミティブは次の方法でクリアされます:

RenderingServer.canvas_item_clear(ci_rid)

メッシュを3D空間にインスタンス化する

3D API は 2D API とは異なるため、インスタンス化 API を使用する必要があります。

extends Node3D


# RenderingServer expects references to be kept around.
var mesh


func _ready():
    # Create a visual instance (for 3D).
    var instance = RenderingServer.instance_create()
    # Set the scenario from the world. This ensures it
    # appears with the same objects as the scene.
    var scenario = get_world_3d().scenario
    RenderingServer.instance_set_scenario(instance, scenario)
    # Add a mesh to it.
    # Remember to keep this reference.
    mesh = load("res://my_mesh.obj")
    RenderingServer.instance_set_base(instance, mesh)
    # Move the mesh around.
    var xform = Transform3D(Basis(), Vector3(2, 3, 0))
    RenderingServer.instance_set_transform(instance, xform)

2D RigidBodyの作成とスプライトの移動

This creates a RigidBody2D using the PhysicsServer2D API, and moves a CanvasItem when the body moves.

# PhysicsServer2D expects references to be kept around.
var body
var shape


func _body_moved(state, index):
    # Created your own canvas item; use it here.
    # `ci_rid` from the sprite example above needs to be moved to a
    # member variable (instead of within `_ready()`) so it can be referenced here.
    RenderingServer.canvas_item_set_transform(ci_rid, state.transform)


func _ready():
    # Create the body.
    body = PhysicsServer2D.body_create()
    PhysicsServer2D.body_set_mode(body, PhysicsServer2D.BODY_MODE_RIGID)
    # Add a shape.
    shape = PhysicsServer2D.rectangle_shape_create()
    # Set rectangle extents.
    PhysicsServer2D.shape_set_data(shape, Vector2(10, 10))
    # Make sure to keep the shape reference!
    PhysicsServer2D.body_add_shape(body, shape)
    # Set space, so it collides in the same space as current scene.
    PhysicsServer2D.body_set_space(body, get_world_2d().space)
    # Move initial position.
    PhysicsServer2D.body_set_state(body, PhysicsServer2D.BODY_STATE_TRANSFORM, Transform2D(0, Vector2(10, 20)))
    # Add the transform callback, when body moves
    # The last parameter is optional, can be used as index
    # if you have many bodies and a single callback.
    PhysicsServer2D.body_set_force_integration_callback(body, self, "_body_moved", 0)

    # Also create a sprite using RenderingServer here.
    # See the section above on creating a sprite.
    # ...

The 3D version should be very similar, as the 2D and 3D physics servers are identical (using RigidBody3D and PhysicsServer3D respectively).

サーバーからデータを取得する

Try to never request any information from RenderingServer, PhysicsServer2D, or PhysicsServer3D by calling functions unless you know what you are doing. These servers will often run asynchronously for performance and calling any function that returns a value will stall them and force them to process anything pending until the function is actually called. This will severely decrease performance if you call them every frame (and it won't be obvious why).

このため、このようなサーバーのほとんどのAPIは、保存可能な実際のデータができるまで、情報を要求することさえできないように設計されています。