UE5 相机后处理材质与动态参数修改

一、完整实现流程

1. 创建后处理材质

1. 材质设置：

   • 在材质编辑器中，将材质域(Material Domain)设为后处理(Post Process)

   • 设置混合位置(Blendable Location)（如After Tonemapping）

   • 创建标量/向量参数（如Intensity, ColorTint）

2. 材质蓝图示例：

[SceneTexture:PostProcessInput0] → [参数控制效果] → [输出节点]

2. 添加后处理材质到相机

方法1：通过相机组件（推荐）

// 创建动态材质实例
UMaterialInstanceDynamic* DynamicMaterial = UMaterialInstanceDynamic::Create(PostProcessMaterial, this);

// 添加到相机组件
if (UCameraComponent* Camera = GetPlayerCamera())
{
    Camera->AddOrUpdateBlendable(DynamicMaterial, 1.0f); // 1.0为权重
}

方法2：通过相机管理器

APlayerCameraManager* CameraManager = UGameplayStatics::GetPlayerCameraManager(GetWorld(), 0);
if (CameraManager)
{
    FWeightedBlendable Blendable;
    Blendable.Object = DynamicMaterial;
    Blendable.Weight = 1.0f;
    CameraManager->GetCameraCacheView().PostProcessSettings.WeightedBlendables.Array.Add(Blendable);
    CameraManager->MarkCameraSettingsDirty(); // 确保更新
}

3. 动态更新材质参数

// 高效参数更新函数
void UpdateMaterialParameter(FName ParamName, float Value)
{
    if (!DynamicMaterial) return;
    
    // 值变化检测避免无效更新
    static float LastValue = MAX_FLT;
    if (FMath::IsNearlyEqual(Value, LastValue, 0.001f)) return;
    
    DynamicMaterial->SetScalarParameterValue(ParamName, Value);
    LastValue = Value;
    
    // 可选：强制刷新（某些版本需要）
    if (UCameraComponent* Camera = GetPlayerCamera())
    {
        Camera->MarkRenderStateDirty();
    }
}

// 使用示例
UpdateMaterialParameter("HitIntensity", FMath::Sin(GetWorld()->GetTimeSeconds()));

4. 移除后处理材质

// 通过相机组件移除
if (UCameraComponent* Camera = GetPlayerCamera())
{
    Camera->RemoveBlendable(DynamicMaterial);
}

// 通过相机管理器移除
if (CameraManager)
{
    FPostProcessSettings& PPSettings = CameraManager->GetCameraCacheView().PostProcessSettings;
    for (int32 i = PPSettings.WeightedBlendables.Array.Num() - 1; i >= 0; i--)
    {
        if (PPSettings.WeightedBlendables.Array[i].Object == DynamicMaterial)
        {
            PPSettings.WeightedBlendables.Array.RemoveAt(i);
            break;
        }
    }
}

二、组件化实现（最佳实践）

#pragma once

#include "CoreMinimal.h"
#include "Components/ActorComponent.h"
#include "PostProcessComponent.generated.h"

UCLASS(ClassGroup=(Rendering), meta=(BlueprintSpawnableComponent))
class YOURPROJECT_API UPostProcessComponent : public UActorComponent
{
    GENERATED_BODY()

public:
    UPostProcessComponent();

protected:
    virtual void BeginPlay() override;
    virtual void EndPlay(const EEndPlayReason::Type EndPlayReason) override;

public:
    UFUNCTION(BlueprintCallable, Category = "Post Process")
    void ActivateEffect(float Duration = 2.0f, float Intensity = 1.0f);
    
    UFUNCTION(BlueprintCallable, Category = "Post Process")
    void SetParameter(FName ParamName, float Value);

private:
    void InitializeMaterial();
    UCameraComponent* GetCamera() const;
    void UpdateCamera();
    
    UPROPERTY(EditAnywhere, Category = "Post Process")
    UMaterialInterface* PostProcessMaterial;
    
    UPROPERTY(Transient)
    UMaterialInstanceDynamic* DynamicMaterial = nullptr;
    
    UCameraComponent* TargetCamera = nullptr;
};

#include "PostProcessComponent.h"
#include "Camera/CameraComponent.h"
#include "Kismet/GameplayStatics.h"

UPostProcessComponent::UPostProcessComponent()
{
    PrimaryComponentTick.bCanEverTick = false;
}

void UPostProcessComponent::BeginPlay()
{
    Super::BeginPlay();
    InitializeMaterial();
}

void UPostProcessComponent::EndPlay(const EEndPlayReason::Type EndPlayReason)
{
    if (DynamicMaterial && TargetCamera)
    {
        TargetCamera->RemoveBlendable(DynamicMaterial);
    }
    Super::EndPlay(EndPlayReason);
}

void UPostProcessComponent::InitializeMaterial()
{
    if (!PostProcessMaterial) return;
    
    DynamicMaterial = UMaterialInstanceDynamic::Create(PostProcessMaterial, this);
    if (!DynamicMaterial) return;
    
    TargetCamera = GetCamera();
    if (TargetCamera)
    {
        TargetCamera->AddOrUpdateBlendable(DynamicMaterial, 1.0f);
    }
}

void UPostProcessComponent::ActivateEffect(float Duration, float Intensity)
{
    if (!DynamicMaterial) return;
    
    // 重置效果权重
    if (TargetCamera)
    {
        TargetCamera->AddOrUpdateBlendable(DynamicMaterial, 1.0f);
    }
    
    // 设置初始参数
    DynamicMaterial->SetScalarParameterValue("Intensity", Intensity);
    
    // 启动定时器自动结束
    GetWorld()->GetTimerManager().SetTimer(EffectTimer, [this]()
    {
        if (TargetCamera)
        {
            TargetCamera->RemoveBlendable(DynamicMaterial);
        }
    }, Duration, false);
}

void UPostProcessComponent::SetParameter(FName ParamName, float Value)
{
    if (DynamicMaterial)
    {
        // 带变化检测的更新
        float CurrentValue;
        if (DynamicMaterial->GetScalarParameterValue(ParamName, CurrentValue) &&
            !FMath::IsNearlyEqual(CurrentValue, Value, 0.001f))
        {
            DynamicMaterial->SetScalarParameterValue(ParamName, Value);
        }
    }
}

UCameraComponent* UPostProcessComponent::GetCamera() const
{
    AActor* Owner = GetOwner();
    if (!Owner) return nullptr;
    
    // 查找相机组件
    UCameraComponent* Camera = Owner->FindComponentByClass<UCameraComponent>();
    if (Camera) return Camera;
    
    // 回退到玩家相机
    if (APlayerController* PC = UGameplayStatics::GetPlayerController(GetWorld(), 0))
    {
        if (APawn* Pawn = PC->GetPawn())
        {
            return Pawn->FindComponentByClass<UCameraComponent>();
        }
    }
    return nullptr;
}

三、常见问题与解决方案

1. 材质不显示

原因：

• 材质域未设置为Post Process
• 相机未启用后处理（bEnablePostProcessing=false）
• 混合权重为0

解决：

// 确保相机启用后处理
if (UCameraComponent* Camera = GetCamera())
{
    Camera->bEnablePostProcessing = true;
}

// 验证材质域
if (DynamicMaterial->GetMaterial()->MaterialDomain != MD_PostProcess)
{
    UE_LOG(LogTemp, Error, TEXT("Material domain must be Post Process!"));
}

2. 参数更新无效

原因：

• 参数名称拼写错误（区分大小写）
• 未使用动态材质实例
• 更新频率过高

解决：

// 验证参数存在
float TempValue;
if (!DynamicMaterial->GetScalarParameterValue("HitIntensity", TempValue))
{
    UE_LOG(LogTemp, Warning, TEXT("Parameter not found!"));
}

// 添加变化检测
void SafeSetParameter(FName Name, float Value)
{
    static TMap<FName, float> LastValues;
    if (!LastValues.Contains(Name)) LastValues.Add(Name, MAX_FLT);
    
    if (!FMath::IsNearlyEqual(Value, LastValues[Name], 0.001f))
    {
        DynamicMaterial->SetScalarParameterValue(Name, Value);
        LastValues[Name] = Value;
    }
}

3. 性能问题

优化策略：

• 参数批量更新：

void SetParameters(TMap<FName, float> Params)
{
    for (auto& Param : Params)
    {
        DynamicMaterial->SetScalarParameterValue(Param.Key, Param.Value);
    }
    // 单次提交
    DynamicMaterial->UpdateParameterValues();
}

• 使用材质参数集合：

// 全局参数控制
UMaterialParameterCollection* GlobalParams = ...;
GetWorld()->GetParameterCollectionInstance(GlobalParams)
    ->SetScalarParameterValue("GlobalIntensity", Value);

四、高级技巧

1. 效果混合与叠加

// 管理多个效果
TMap<FName, UMaterialInstanceDynamic*> ActiveEffects;

void AddEffect(FName EffectID, UMaterialInterface* Material)
{
    UMaterialInstanceDynamic* NewMID = UMaterialInstanceDynamic::Create(Material, this);
    ActiveEffects.Add(EffectID, NewMID);
    
    if (UCameraComponent* Camera = GetCamera())
    {
        Camera->AddOrUpdateBlendable(NewMID, 1.0f);
    }
}

void RemoveEffect(FName EffectID)
{
    if (UMaterialInstanceDynamic** MIDPtr = ActiveEffects.Find(EffectID))
    {
        if (UCameraComponent* Camera = GetCamera())
        {
            Camera->RemoveBlendable(*MIDPtr);
        }
        ActiveEffects.Remove(EffectID);
    }
}

2. 基于距离的LOD控制

void UpdateEffectLOD()
{
    FVector PlayerLocation = ...;
    float Distance = FVector::Distance(GetOwner()->GetActorLocation(), PlayerLocation);
    float Intensity = FMath::Clamp(1.0f - (Distance / MaxDistance), 0.0f, 1.0f);
    
    if (DynamicMaterial)
    {
        DynamicMaterial->SetScalarParameterValue("EffectIntensity", BaseIntensity * Intensity);
        
        // 完全禁用远距离效果
        if (Intensity < 0.01f)
        {
            if (UCameraComponent* Camera = GetCamera())
            {
                Camera->RemoveBlendable(DynamicMaterial);
            }
        }
    }
}

3. 后处理材质动画

// 在tick中创建动画效果
void TickComponent(float DeltaTime, ELevelTick TickType, FActorComponentTickFunction* ThisTickFunction)
{
    Super::TickComponent(DeltaTime, TickType, ThisTickFunction);
    
    if (bIsAnimating)
    {
        AnimationTime += DeltaTime;
        float Pulse = FMath::Sin(AnimationTime * 5.0f) * 0.5f + 0.5f;
        DynamicMaterial->SetScalarParameterValue("PulseIntensity", Pulse);
        
        if (AnimationTime > AnimationDuration)
        {
            bIsAnimating = false;
        }
    }
}

五、总结与最佳实践

1. 材质设置：

• 务必设置材质域为Post Process

• 使用暴露参数而非硬编码值

2. 生命周期管理：

virtual void BeginPlay() override;  // 初始化
virtual void EndPlay() override;     // 清理资源

3. 性能优化：

• 使用变化检测减少更新次数
• 批量更新材质参数
• 远距离禁用效果

4. 错误预防：

// 安全访问模式
if (DynamicMaterial && GetCamera())
{
    // 操作
}

5. 调试工具：

// 控制台命令
r.PostProcessing.Debug 1  // 显示活动后处理
r.PostProcess 0           // 禁用所有后处理