Extents Modifier 和 Bounds Modifier这两个节点看起来很像，都是修改Point的Bouding Box，查看一下源代码，简单看一下它们的区别
文章目录
- 两个节点的代码对比
- Bounds Modifier
- 源代码
- Bounds Modifier
- 源代码
- 小结
两个节点的代码对比
Bounds Modifier
源代码
switch (Mode){case EPCGBoundsModifierMode::Intersect:ProcessPoints(Context, Inputs, Outputs, [&Bounds, bAffectSteepness, Steepness](const FPCGPoint& InPoint, FPCGPoint& OutPoint){OutPoint = InPoint;OutPoint.SetLocalBounds(InPoint.GetLocalBounds().Overlap(Bounds));if (bAffectSteepness){OutPoint.Steepness = FMath::Min(InPoint.Steepness, Steepness);}return true;});break;case EPCGBoundsModifierMode::Include:ProcessPoints(Context, Inputs, Outputs, [&Bounds, bAffectSteepness, Steepness](const FPCGPoint& InPoint, FPCGPoint& OutPoint){OutPoint = InPoint;OutPoint.SetLocalBounds(InPoint.GetLocalBounds() + Bounds);if (bAffectSteepness){OutPoint.Steepness = FMath::Max(InPoint.Steepness, Steepness);}return true;});break;case EPCGBoundsModifierMode::Translate:ProcessPoints(Context, Inputs, Outputs, [&BoundsMin, &BoundsMax, bAffectSteepness, Steepness](const FPCGPoint& InPoint, FPCGPoint& OutPoint){OutPoint = InPoint;OutPoint.BoundsMin += BoundsMin;OutPoint.BoundsMax += BoundsMax;if (bAffectSteepness){OutPoint.Steepness = FMath::Clamp(InPoint.Steepness + Steepness, 0.0f, 1.0f);}return true;});break;case EPCGBoundsModifierMode::Scale:ProcessPoints(Context, Inputs, Outputs, [&BoundsMin, &BoundsMax, bAffectSteepness, Steepness](const FPCGPoint& InPoint, FPCGPoint& OutPoint){OutPoint = InPoint;OutPoint.BoundsMin *= BoundsMin;OutPoint.BoundsMax *= BoundsMax;if (bAffectSteepness){OutPoint.Steepness = FMath::Clamp(InPoint.Steepness * Steepness, 0.0f, 1.0f);}return true;});break;case EPCGBoundsModifierMode::Set:ProcessPoints(Context, Inputs, Outputs, [&Bounds, bAffectSteepness, Steepness](const FPCGPoint& InPoint, FPCGPoint& OutPoint){OutPoint = InPoint;OutPoint.SetLocalBounds(Bounds);if (bAffectSteepness){OutPoint.Steepness = Steepness;}return true;});break;}Bounds Modifier
源代码
switch (Mode){case EPCGPointExtentsModifierMode::Minimum:ProcessPoints(Context, Inputs, Outputs, [Extents](const FPCGPoint& InPoint, FPCGPoint& OutPoint){OutPoint = InPoint;OutPoint.SetExtents(FVector::Min(Extents, InPoint.GetExtents()));return true;});break;case EPCGPointExtentsModifierMode::Maximum:ProcessPoints(Context, Inputs, Outputs, [Extents](const FPCGPoint& InPoint, FPCGPoint& OutPoint){OutPoint = InPoint;OutPoint.SetExtents(FVector::Max(Extents, InPoint.GetExtents()));return true;});break;case EPCGPointExtentsModifierMode::Add:ProcessPoints(Context, Inputs, Outputs, [Extents](const FPCGPoint& InPoint, FPCGPoint& OutPoint){OutPoint = InPoint;OutPoint.SetExtents(Extents + InPoint.GetExtents());return true;});break;case EPCGPointExtentsModifierMode::Multiply:ProcessPoints(Context, Inputs, Outputs, [Extents](const FPCGPoint& InPoint, FPCGPoint& OutPoint){OutPoint = InPoint;OutPoint.SetExtents(Extents * InPoint.GetExtents());return true;});break;case EPCGPointExtentsModifierMode::Set:ProcessPoints(Context, Inputs, Outputs, [Extents](const FPCGPoint& InPoint, FPCGPoint& OutPoint){OutPoint = InPoint;OutPoint.SetExtents(Extents);return true;});break;}
从代码上看，除了运算模式的区别，和它们的名字一样Bounds Modifier操作的目标是Point的Bounds而Extents Modifier 操作的目标是Point的Extents，并且Bounds Modifier可以选择性地影响Steepness，而Extents Modifier没有这个选项。所以问题的关键就是Bounds和Extents的区别。下面我们看一下PCGPoint的代码:
USTRUCT(BlueprintType)
struct PCG_API FPCGPoint
{GENERATED_BODY()
public:FPCGPoint() = default;FPCGPoint(const FTransform& InTransform, float InDensity, int32 InSeed);FBox GetLocalBounds() const;FBox GetLocalDensityBounds() const;void SetLocalBounds(const FBox& InBounds);FBoxSphereBounds GetDensityBounds() const;UPROPERTY(BlueprintReadWrite, EditAnywhere, Category = Properties)FTransform Transform;UPROPERTY(BlueprintReadWrite, EditAnywhere, Category = Properties)float Density = 1.0f;UPROPERTY(BlueprintReadWrite, EditAnywhere, Category = Properties)FVector BoundsMin = -FVector::One();UPROPERTY(BlueprintReadWrite, EditAnywhere, Category = Properties)FVector BoundsMax = FVector::One();UPROPERTY(BlueprintReadWrite, EditAnywhere, Category = Properties)FVector4 Color = FVector4::One();UPROPERTY(BlueprintReadWrite, EditAnywhere, Category = Properties, meta = (ClampMin = "0", ClampMax = "1"))float Steepness = 0.5f;UPROPERTY(BlueprintReadWrite, EditAnywhere, Category = Properties)int32 Seed = 0;UPROPERTY(BlueprintReadOnly, VisibleAnywhere, Category = "Properties|Metadata")int64 MetadataEntry = -1;FVector GetExtents() const { return (BoundsMax - BoundsMin) / 2.0; }void SetExtents(const FVector& InExtents){const FVector Center = GetLocalCenter();BoundsMin = Center - InExtents;BoundsMax = Center + InExtents;}FVector GetScaledExtents() const { return GetExtents() * Transform.GetScale3D(); }FVector GetLocalCenter() const { return (BoundsMax + BoundsMin) / 2.0; }void SetLocalCenter(const FVector& InCenter){const FVector Delta = InCenter - GetLocalCenter();BoundsMin += Delta;BoundsMax += Delta;}using PointCustomPropertyGetter = TFunction<bool(const FPCGPoint&, void*)>;using PointCustomPropertySetter = TFunction<bool(FPCGPoint&, const void*)>;static bool HasCustomPropertyGetterSetter(FName Name);static TUniquePtr<IPCGAttributeAccessor> CreateCustomPropertyAccessor(FName Name);
};
在Point中并没有Extents这个成员变量，而只有BoundsMin和BoundsMax这两个Vector3的成员变量
UPROPERTY(BlueprintReadWrite, EditAnywhere, Category = Properties)FVector BoundsMin = -FVector::One();UPROPERTY(BlueprintReadWrite, EditAnywhere, Category = Properties)FVector BoundsMax = FVector::One();
Extents和Bounds之间的关系：
FVector GetExtents() const { return (BoundsMax - BoundsMin) / 2.0; }
void SetExtents(const FVector& InExtents){const FVector Center = GetLocalCenter();BoundsMin = Center - InExtents;BoundsMax = Center + InExtents;}
小结
Extents Modifier 和 Bounds Modifier的本质并没有区别
