IN THIS ARTICLE

Multiplayer Auto-components

Auto-components provide a convenient way to define states of a multiplayer component relevant to network synchronization. Using the AzAutoGen system, auto-component files found inside of your project are processed during builds to create C++ classes for components and controllers that provide network replication and remote function calls. Auto-components also take care of Editor and behavior context bindings so that the bound component shows in the Editor and works with O3DE scripting.

In order to enable auto-component builds for your project, follow the instructions in Multiplayer Project Configuration .

Auto-component file structure

Auto-components are defined in XML files, placed in the Code\Source\Autogen directory of the Multiplayer Gem.

Component attributes

The Component tag defines the name, namespace, include path, and override behavior for the multiplayer component being described.

Property	Description	Type
Name	The class name of the generated auto-component.	`string`: Must be a valid C++ class name.
Namespace	The namespace the generated auto-component will be placed within. For a given Gem, all defined auto-components must be defined within the same namespace. Mixing namespaces inside a Gem will result in compiler errors.	`string`: Must be a valid C++ namespace name.
OverrideComponent	If `true`, the generated component will be a base class and the developer implementing the multiplayer component will be responsible for supplying the final derived component used in the editor and at runtime.	`bool`
OverrideController	If `true`, the generated controller will be a base class, and the developer implementing the multiplayer component will be responsible for supplying the final derived controller used in the runtime.	`bool`
OverrideInclude	If either `OverrideComponent` or `OverrideController` are `true`, this value is required and must be the path (relative to the Gem root) of the header containing the concrete implementations.	the developer implementing the final component or controller classes must provide the class header the final classes are declared within.	`string`

ComponentRelation

A component relation (the ComponentRelation tag) describes how various components may be related to the component being described.

Property	Description	Type
Name	The name of the related component.	`string`: Must be a valid C++ class name.
Namespace	The namespace the related component is declared within.	`string`: Must be a valid C++ namespace.
Include	The include path of the related component.	`string`
Constraint	The type of relation this entry has with the component being described. The allowed values are:	`Required`, `Weak`, `Incompatible`
	Required: The related component must be present on the entity. These components are displayed in the Editor as a hard requirement for adding this autocomponent.
	Weak: The related component isn’t required, but will be activated on the entity (if present) before this auto-component.
	Incompatible: The related component isn’t compatible with this auto-component. Attempting to place both components on an entity will result in an error.
HasController	If `true`, the related component must have a multiplayer controller associated with it. Setting this value to true will cause controller accessors to be generated on the controller being described.	`bool`

For components which have a relation constraint of Required or Weak, accessors are generated on the auto-component with the name Get<ComponentName>(). These accessors return a cached pointer to the related component, created on entity activation.

Include

The Include tag is used to generate the #includes of the C++ code. Use an Include tag for each header that your generated classes will use.

Property	Description	Type
File	The path to a header to add as an `#include` of the generated source.	`string`

To do:
Document the following parts of auto-components:
NetworkInput
NetworkProperty
ArchetypeProperty
RemoteProcedure
A GitHub issue has been created for this task here.

Example

The following is an example of an auto-component which synchronizes a component representing weapon state across a multiplayer session.

<?xml version="1.0"?>

<Component
    Name="NetworkWeaponsComponent"
    Namespace="MultiplayerSample"
    OverrideComponent="true"
    OverrideController="true"
    OverrideInclude="Source/Components/NetworkWeaponsComponent.h"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">

    <ComponentRelation Constraint="Required" HasController="true" Name="NetworkAnimationComponent" Namespace="MultiplayerSample" Include="Source/Components/NetworkAnimationComponent.h" />

    <Include File="Source/Weapons/WeaponTypes.h" />

    <NetworkInput Type="bool" Name="Draw" Init="false" />
    <NetworkInput Type="WeaponActivationBitset" Name="Firing"  Init="" />

    <NetworkProperty Type="AZ::Vector3"  Name="TargetPosition"   Init="AZ::Vector3::CreateZero()" Container="Object"       ReplicateFrom="Authority" ReplicateTo="Client"     IsPublic="false" IsRewindable="false" IsPredictable="false" ExposeToEditor="false" GenerateEventBindings="false" Description="Target position the weapons component is currently aiming at" />
    <NetworkProperty Type="FireParams"   Name="ActivationParams" Init=""  Container="Array" Count="MaxWeaponsPerComponent" ReplicateFrom="Authority" ReplicateTo="Client"     IsPublic="false" IsRewindable="false" IsPredictable="false" ExposeToEditor="false" GenerateEventBindings="false" Description="Parameters for the current weapon activation" />
    <NetworkProperty Type="uint8_t"      Name="ActivationCounts" Init="0" Container="Array" Count="MaxWeaponsPerComponent" ReplicateFrom="Authority" ReplicateTo="Client"     IsPublic="false" IsRewindable="false" IsPredictable="false" ExposeToEditor="false" GenerateEventBindings="false" Description="The number of activations" />
    <NetworkProperty Type="WeaponState"  Name="WeaponStates"     Init=""  Container="Array" Count="MaxWeaponsPerComponent" ReplicateFrom="Authority" ReplicateTo="Autonomous" IsPublic="false" IsRewindable="false" IsPredictable="true"  ExposeToEditor="false" GenerateEventBindings="false" Description="The predictable states of the weapons" />

    <ArchetypeProperty Type="WeaponParams" Name="WeaponParams"  Init=""           Container="Array" Count="MaxWeaponsPerComponent" ExposeToEditor="true" Description="Parameters for the weapons attached to this NetworkWeaponsComponent" />
    <ArchetypeProperty Type="AZ::Name"     Name="FireBoneNames" Init="AZ::Name()" Container="Array" Count="MaxWeaponsPerComponent" ExposeToEditor="true" Description="Name of the bone to attach to for fire events" />

    <RemoteProcedure Name="SendConfirmHit" InvokeFrom="Authority" HandleOn="Client" IsPublic="false" IsReliable="false" GenerateEventBindings="false" Description="Single hit event confirmed by the server" >
        <Param Type="WeaponIndex" Name="WeaponIndex" />
        <Param Type="HitEvent"    Name="HitEvent" />
    </RemoteProcedure>

    <RemoteProcedure Name="SendConfirmProjectileHit" InvokeFrom="Authority" HandleOn="Client" IsPublic="false" IsReliable="false" GenerateEventBindings="false" Description="Fired by projectile entities on confirmed hit" >
        <Param Type="WeaponIndex" Name="WeaponIndex" />
        <Param Type="HitEvent"    Name="HitEvent" />
    </RemoteProcedure>
</Component>