355 lines
16 KiB
Markdown
355 lines
16 KiB
Markdown
## UGameplayEffect
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UGameplayEffect在框架中主要负责各种数值上的效果，如果技能cd、类似黑魂中的异常效果堆叠与buff，甚至连角色升级时的属性点添加都可以使用它来实现。
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因为大多数逻辑都是设置数据子类的操作，所以对于这个类，本人推荐使用蓝图来进行操作。
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## 简单使用教程
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通过继承UGameplayEffect来创建一个新的GameplayEffect类，并在构造函数中对相应的属性进行设置。之后在Ability类中调用ApplyGameplayEffectToOwner函数让GameplayEffect生效。
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```
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if (CommitAbility(Handle, ActorInfo, ActivationInfo)) // ..then commit the ability...
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{
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// Then do more stuff...
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const UGameplayEffect* GameplayEffect = NewObject<UGE_DamageBase>();
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ApplyGameplayEffectToOwner(CurrentSpecHandle, CurrentActorInfo, CurrentActivationInfo, GameplayEffect, 5, 1);
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K2_EndAbility();
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}
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```
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具体操作可以参考ActionRPG模板，或者是我的项目代码。
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## Modifiers
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本质是一个FGameplayModifierInfo结构体数组用于存储所有数值修改信息。FGameplayModifierInfo包含以下属性：
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- Attribute 修改的目标属性集中的属性。
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- ModifierOp 修改方式。例如Override、Add、Multiply。
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- Magnitude（已被废弃）
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- ModifierMagnitude 修改的数值与类型，可以配置数据表。
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- EvaluationChannelSettings （不知道为什么没在编辑器中显示，而且代码中只有一处调用，所以直接跳过）
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- SourceTags 本身标签行为（Effect生效所需或者忽略的标签）
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- TargetTags 目标标签行为（Effect生效所需或者忽略的标签）
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可以看得出ModifierMagnitude才是Modifiers的关键，而它的本质是FGameplayEffectModifierMagnitude结构体。但是我们只需要学会初始化它即可。它具有以下四种类型：
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- ScalableFloat 较为简单的使用方式，使用ScalableFloat进行计算
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- AttributeBased 基于属性执行计算。
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- CustomCalculationClass 能够捕获多个属性进行自定义计算
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- SetByCaller 被蓝图或者代码显式设置
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### ScalableFloat的调用示例
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ScalableFloat类型是用于设置固定值的简单方式，同时它也支持通过CurveTable配合技能等级设置倍率。（最后结果=固定值*倍率）当然如果你向完全通过CurveTable来控制参数，那就把固定值设置为1即可。
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```
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FGameplayModifierInfo info;
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info.Attribute = FGameplayAttribute(FindFieldChecked<UProperty>(URPGAttributeSet::StaticClass(), GET_MEMBER_NAME_CHECKED(URPGAttributeSet, Health)));
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info.ModifierOp = EGameplayModOp::Additive;
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//固定值
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//info.ModifierMagnitude = FGameplayEffectModifierMagnitude(FScalableFloat(100.0));
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//CurveTable控制倍率
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FScalableFloat damageValue = {1.0};
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FCurveTableRowHandle damageCurve;
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static ConstructorHelpers::FObjectFinder<UCurveTable> curveAsset(TEXT("/Game/ActionRPG/DataTable/Damage"));
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damageCurve.CurveTable = curveAsset.Object;
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damageCurve.RowName = FName("Damage");
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damageValue.Curve = damageCurve;
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info.ModifierMagnitude = FGameplayEffectModifierMagnitude(damageValue);
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Modifiers.Add(info);
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```
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PS.技能等级在ApplyGameplayEffectToOwner函数中设置。
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### AttributeBased的调用示例
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最终计算过程可以在CalculateMagnitude函数中找到。
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1. 如果尝试捕获到数值（不为None），则将赋值给AttribValue。
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2. 判断AttributeCalculationType，来计算对应的AttribValue。（我不太了解代码中channel的概念，如果channel不存在，AttribValue为原本值）
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3. 如果AttributeCurve存在，则将AttribValue作为x轴值来查找y轴值，并进行插值计算，最后将结果赋值给AttribValue。
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4. 最终计算公式：`$((Coefficient * (AttribValue + PreMultiplyAdditiveValue)) + PostMultiplyAdditiveValue)$`
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### BackingAttribute
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为GameplayEffect捕获GameplayAttribute的选项。（你可以理解为Lambda表达式的捕获）
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- AttributeToCapture：捕获属性
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- AttributeSource：捕获的目标（自身还是目标对象）
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- bSnapshot：属性是否需要被快照（没仔细看，如果为false，每次都会重新获取吧）
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### AttributeCalculationType
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默认值为AttributeMagnitude。
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- AttributeMagnitude：使用最后通过属性计算出来的级数
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- AttributeBaseValue：使用属性基础值
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- AttributeBonusMagnitude：使用（最后计算值-基础值）
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- AttributeMagnitudeEvaluatedUpToChannel：不清楚使用方法，关键是在编辑器中，这个选项默认是不显示的
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```
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FGameplayModifierInfo info;
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info.Attribute = FGameplayAttribute(FindFieldChecked<UProperty>(URPGAttributeSet::StaticClass(), GET_MEMBER_NAME_CHECKED(URPGAttributeSet, Health)));
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info.ModifierOp = EGameplayModOp::Additive;
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FAttributeBasedFloat damageValue;
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damageValue.Coefficient = { 1.2f };
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damageValue.PreMultiplyAdditiveValue = { 1.0f };
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damageValue.PostMultiplyAdditiveValue = { 2.0f };
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damageValue.BackingAttribute = FGameplayEffectAttributeCaptureDefinition(FGameplayAttribute(FindFieldChecked<UProperty>(URPGAttributeSet::StaticClass(), GET_MEMBER_NAME_CHECKED(URPGAttributeSet, Health)))
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, EGameplayEffectAttributeCaptureSource::Source, false);
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FCurveTableRowHandle damageCurve;
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static ConstructorHelpers::FObjectFinder<UCurveTable> curveAsset(TEXT("/Game/ActionRPG/DataTable/Damage"));
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damageCurve.CurveTable = curveAsset.Object;
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damageCurve.RowName = FName("Damage");
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damageValue.AttributeCurve = damageCurve;
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damageValue.AttributeCalculationType = EAttributeBasedFloatCalculationType::AttributeMagnitude;
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info.ModifierMagnitude = damageValue;
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Modifiers.Add(info);
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```
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### CustomCalculationClass的调用示例
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与AttributeCalculationType相比，少了属性捕获，多了CalculationClassMagnitude（UGameplayModMagnitudeCalculation类）。
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```
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FGameplayModifierInfo info;
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info.Attribute = FGameplayAttribute(FindFieldChecked<UProperty>(URPGAttributeSet::StaticClass(), GET_MEMBER_NAME_CHECKED(URPGAttributeSet, Health)));
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info.ModifierOp = EGameplayModOp::Additive;
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FCustomCalculationBasedFloat damageValue;
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damageValue.CalculationClassMagnitude = UDamageMagnitudeCalculation::StaticClass();
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damageValue.Coefficient = { 1.2f };
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damageValue.PreMultiplyAdditiveValue = { 1.0f };
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damageValue.PostMultiplyAdditiveValue = { 2.0f };
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info.ModifierMagnitude = damageValue;
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Modifiers.Add(info);
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```
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PS.如果这个计算过程还取决于外部非GameplayAbility框架的条件，那么你可能需要重写GetExternalModifierDependencyMulticast()函数，以获得FOnExternalGameplayModifierDependencyChange委托。从而实现：当外部条件发生改变时，及时更新计算结果。
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### UGameplayModMagnitudeCalculation
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你可以通过继承UGameplayModMagnitudeCalculation来创建自定义的Calculation类。所需实现步骤如下：
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1. 在构造函数中，向RelevantAttributesToCapture数组添加需要捕获的属性。
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2. 实现CalculateBaseMagnitude事件。（因为BlueprintNativeEvent类型，所以既可以在c++里实现也可以在蓝图中实现，关于两者结合可以参考UGameplayAbility类中ActivateAbility()的写法。
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案例代码如下：
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```
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UCLASS(BlueprintType, Blueprintable, Abstract)
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class ACTIONRPG_API UDamageMagnitudeCalculation : public UGameplayModMagnitudeCalculation
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{
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GENERATED_BODY()
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public:
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UDamageMagnitudeCalculation();
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float CalculateBaseMagnitude_Implementation(const FGameplayEffectSpec& Spec) const override;
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};
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```
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```
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UDamageMagnitudeCalculation::UDamageMagnitudeCalculation()
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{
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RelevantAttributesToCapture.Add(FGameplayEffectAttributeCaptureDefinition(FGameplayAttribute(FindFieldChecked<UProperty>(URPGAttributeSet::StaticClass(), GET_MEMBER_NAME_CHECKED(URPGAttributeSet, Health)))
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, EGameplayEffectAttributeCaptureSource::Source, false));
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}
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float UDamageMagnitudeCalculation::CalculateBaseMagnitude_Implementation(const FGameplayEffectSpec& Spec) const
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{
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float damage{ 0.0f};
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FAggregatorEvaluateParameters InEvalParams;
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//捕获失败的容错语句
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if (!GetCapturedAttributeMagnitude(FGameplayEffectAttributeCaptureDefinition(FGameplayAttribute(FindFieldChecked<UProperty>(URPGAttributeSet::StaticClass(), GET_MEMBER_NAME_CHECKED(URPGAttributeSet, Health)))
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, EGameplayEffectAttributeCaptureSource::Source, false), Spec, InEvalParams, damage)) {
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//如果这个变量会作为除数的话，不能为0
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damage = 1.0f;
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}
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return damage;
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}
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```
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## Executions
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Executions更为简单，而且更加自由。只需要编写Calculation Class即可。它与Modifiers的不同之处在于：一个Modifiers只能修改一个属性，而Executions可以同时改动多个属性。
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### UGameplayEffectExecutionCalculation
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这里我就直接复制actionRPG模板的代码了。
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开头的RPGDamageStatics结构体与DamageStatics函数，可以减少后面的代码量。可以算是FGameplayEffectAttributeCaptureDefinition的语法糖吧。
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```
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UCLASS()
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class ACTIONRPG_API UDamageExecutionCalculation : public UGameplayEffectExecutionCalculation
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{
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GENERATED_BODY()
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public:
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UDamageExecutionCalculation();
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virtual void Execute_Implementation(const FGameplayEffectCustomExecutionParameters& ExecutionParams, OUT FGameplayEffectCustomExecutionOutput& OutExecutionOutput) const override;
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};
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```
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```
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struct RPGDamageStatics
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{
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DECLARE_ATTRIBUTE_CAPTUREDEF(DefensePower);
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DECLARE_ATTRIBUTE_CAPTUREDEF(AttackPower);
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DECLARE_ATTRIBUTE_CAPTUREDEF(Damage);
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RPGDamageStatics()
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{
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// Capture the Target's DefensePower attribute. Do not snapshot it, because we want to use the health value at the moment we apply the execution.
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DEFINE_ATTRIBUTE_CAPTUREDEF(URPGAttributeSet, DefensePower, Target, false);
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// Capture the Source's AttackPower. We do want to snapshot this at the moment we create the GameplayEffectSpec that will execute the damage.
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// (imagine we fire a projectile: we create the GE Spec when the projectile is fired. When it hits the target, we want to use the AttackPower at the moment
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// the projectile was launched, not when it hits).
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DEFINE_ATTRIBUTE_CAPTUREDEF(URPGAttributeSet, AttackPower, Source, true);
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// Also capture the source's raw Damage, which is normally passed in directly via the execution
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DEFINE_ATTRIBUTE_CAPTUREDEF(URPGAttributeSet, Damage, Source, true);
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}
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};
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static const RPGDamageStatics& DamageStatics()
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{
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static RPGDamageStatics DmgStatics;
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return DmgStatics;
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}
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UDamageExecutionCalculation::UDamageExecutionCalculation()
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{
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RelevantAttributesToCapture.Add(DamageStatics().DefensePowerDef);
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RelevantAttributesToCapture.Add(DamageStatics().AttackPowerDef);
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RelevantAttributesToCapture.Add(DamageStatics().DamageDef);
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}
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void UDamageExecutionCalculation::Execute_Implementation(const FGameplayEffectCustomExecutionParameters& ExecutionParams, OUT FGameplayEffectCustomExecutionOutput& OutExecutionOutput) const
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{
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UAbilitySystemComponent* TargetAbilitySystemComponent = ExecutionParams.GetTargetAbilitySystemComponent();
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UAbilitySystemComponent* SourceAbilitySystemComponent = ExecutionParams.GetSourceAbilitySystemComponent();
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AActor* SourceActor = SourceAbilitySystemComponent ? SourceAbilitySystemComponent->AvatarActor : nullptr;
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AActor* TargetActor = TargetAbilitySystemComponent ? TargetAbilitySystemComponent->AvatarActor : nullptr;
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const FGameplayEffectSpec& Spec = ExecutionParams.GetOwningSpec();
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// Gather the tags from the source and target as that can affect which buffs should be used
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const FGameplayTagContainer* SourceTags = Spec.CapturedSourceTags.GetAggregatedTags();
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const FGameplayTagContainer* TargetTags = Spec.CapturedTargetTags.GetAggregatedTags();
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FAggregatorEvaluateParameters EvaluationParameters;
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EvaluationParameters.SourceTags = SourceTags;
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EvaluationParameters.TargetTags = TargetTags;
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// --------------------------------------
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// Damage Done = Damage * AttackPower / DefensePower
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// If DefensePower is 0, it is treated as 1.0
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// --------------------------------------
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//计算捕获属性的数值。
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float DefensePower = 0.f;
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ExecutionParams.AttemptCalculateCapturedAttributeMagnitude(DamageStatics().DefensePowerDef, EvaluationParameters, DefensePower);
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//因为要做除数所以需要加入容错语句
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if (DefensePower == 0.0f)
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{
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DefensePower = 1.0f;
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}
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float AttackPower = 0.f;
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ExecutionParams.AttemptCalculateCapturedAttributeMagnitude(DamageStatics().AttackPowerDef, EvaluationParameters, AttackPower);
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float Damage = 0.f;
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ExecutionParams.AttemptCalculateCapturedAttributeMagnitude(DamageStatics().DamageDef, EvaluationParameters, Damage);
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//伤害计算公式
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float DamageDone = Damage * AttackPower / DefensePower;
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if (DamageDone > 0.f)
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{
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//这里可以修改多个属性
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OutExecutionOutput.AddOutputModifier(FGameplayModifierEvaluatedData(DamageStatics().DamageProperty, EGameplayModOp::Additive, DamageDone));
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}
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}
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```
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## Period
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Period指的是周期，一般用于制作周期性技能。
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```
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//持续类型，只有设置为HasDuration，技能才能变成周期性的
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DurationPolicy = EGameplayEffectDurationType::HasDuration;
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//持续时间
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DurationMagnitude = FGameplayEffectModifierMagnitude(1.0);
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//周期，技能生效次数=持续时间/周期
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Period = 2.0;
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```
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# FGameplayEffectContainer与Spec
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EPIC实现了这个结构体
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调用URPGGameplayAbility::MakeEffectContainerSpecFromContainer
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使用FGameplayEffectContainer生成FGameplayEffectContainerSpec结构体。
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Spec是实例版本，存储TargetDataHandle与EffectSpecHandle。通过MakeEffectContainerSpecFromContainer进行实例化（但本质是通过Spec的AddTarget进行数据填充）。
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之后再通过
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```
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ReturnSpec.TargetGameplayEffectSpecs.Add(MakeOutgoingGameplayEffectSpec(EffectClass, OverrideGameplayLevel));
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```
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填充EffectSpec数据。
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**MakeEffectContainerSpec则是个快捷函数**
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通过FGameplayTag寻找对应的Effect与Target数据。EventData则用于调用TargetType类的GetTarget函数，用于获取符合要求的目标（Actor）。
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在ActionRPG中URPGTargetType_UseEventData的GetTarget用到了EventData。大致逻辑为首先寻找EventData里是否带有EventData.HitResult信息（可以在Send Event To Actor中设置），如果没有则返回EventData.Target信息。
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```
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void URPGTargetType_UseEventData::GetTargets_Implementation(ARPGCharacterBase* TargetingCharacter, AActor* TargetingActor, FGameplayEventData EventData, TArray<FHitResult>& OutHitResults, TArray<AActor*>& OutActors) const
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{
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const FHitResult* FoundHitResult = EventData.ContextHandle.GetHitResult();
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if (FoundHitResult)
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{
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OutHitResults.Add(*FoundHitResult);
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}
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else if (EventData.Target)
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{
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OutActors.Add(const_cast<AActor*>(EventData.Target));
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}
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}
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```
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ApplyEffectContainer则是个方便函数。
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# 实现在AnimNotify中向指定目标引用GameplayEffect
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从GameplayAbilityComponent或者从GameplayAbility中设置.
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MakeOutgoingGameplayEffectSpec=>
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ApplyGameplayEffectSpecToTarget 位于UGameplayAbility
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ApplyGameplayEffectToTarget
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GameplayEffectSpec.GetContext().AddTarget()
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RemoveGrantedByEffect()函数可以移除Ability中Instance类型的Effect。非常适合来清除翻滚免伤、技能硬直效果。
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```
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FRPGGameplayEffectContainerSpec URPGBlueprintLibrary::AddTargetsToEffectContainerSpec(const FRPGGameplayEffectContainerSpec& ContainerSpec, const TArray<FHitResult>& HitResults, const TArray<AActor*>& TargetActors)
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{
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FRPGGameplayEffectContainerSpec NewSpec = ContainerSpec;
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NewSpec.AddTargets(HitResults, TargetActors);
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return NewSpec;
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}
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TArray<FActiveGameplayEffectHandle> URPGBlueprintLibrary::ApplyExternalEffectContainerSpec(const FRPGGameplayEffectContainerSpec& ContainerSpec)
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{
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TArray<FActiveGameplayEffectHandle> AllEffects;
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// Iterate list of gameplay effects
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for (const FGameplayEffectSpecHandle& SpecHandle : ContainerSpec.TargetGameplayEffectSpecs)
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{
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if (SpecHandle.IsValid())
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{
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// If effect is valid, iterate list of targets and apply to all
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for (TSharedPtr<FGameplayAbilityTargetData> Data : ContainerSpec.TargetData.Data)
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{
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AllEffects.Append(Data->ApplyGameplayEffectSpec(*SpecHandle.Data.Get()));
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}
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}
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}
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return AllEffects;
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}
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```
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```
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FGameplayEffectSpecHandle SpecHandle = MakeOutgoingGameplayEffectSpec(Handle, ActorInfo, ActivationInfo, GameplayEffectClass, GameplayEffectLevel);
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if (SpecHandle.Data.IsValid())
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{
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SpecHandle.Data->StackCount = Stacks;
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SCOPE_CYCLE_UOBJECT(Source, SpecHandle.Data->GetContext().GetSourceObject());
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EffectHandles.Append(ApplyGameplayEffectSpecToTarget(Handle, ActorInfo, ActivationInfo, SpecHandle, Target));
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}
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```
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# 实用函数
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Wait Input Release
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