Unreal engine 4 C++ 一些调试用的绘制函数

UE4中提供了很多预定义的调试绘制函数，在做调试的时候还是比较方便的。可以在场景里绘制点、线、圆、球、箭头、椎体、胶囊、甚至样条线、字符串、网格等等，基本上该有的都有了。比较赞的是，你能控制线条的厚度，调试的时候就比较直观了。

要使用这些函数，只需要包含DrawDebugHelpers.h 头文件即可。下面介绍几个主要的绘制函数：

1.绘制点

ENGINE_API void DrawDebugPoint(const UWorld* InWorld, FVector const& Position, float Size, FColor const& PointColor, bool bPersistentLines = false, float LifeTime=-1.f, uint8 DepthPriority = 0);

可选参数里面，我们可以控制点的尺寸、颜色、持续时间等。bPersistentLines表示，当前绘制的整个对象，是不是持久对象，设为true，它会一直显示当前World，直到你调用下面这个方法，释放它：

 void FlushPersistentDebugLines(const UWorld* InWorld);

其他的绘制函数，此参数意义都是一样的。

2.绘制线

ENGINE_API void DrawDebugLine(const UWorld* InWorld, FVector const& LineStart, FVector const& LineEnd, FColor const& Color, bool bPersistentLines = false, float LifeTime=-1.f, uint8 DepthPriority = 0, float Thickness = 0.f);

注意Thickness这个参数，它控制线条的厚度。

3.绘制箭头

ENGINE_API void DrawDebugDirectionalArrow(const UWorld* InWorld, FVector const& LineStart, FVector const& LineEnd, float ArrowSize, FColor const& Color, bool bPersistentLines = false, float LifeTime=-1.f, uint8 DepthPriority = 0);

这个函数绘制一个有向箭头，和绘制线差不多，ArrowSize是箭头的尺寸。

4.绘制Box

ENGINE_API void DrawDebugBox(const UWorld* InWorld, FVector const& Center, FVector const& Extent, FColor const& Color, bool bPersistentLines = false, float LifeTime=-1.f, uint8 DepthPriority = 0);/** Draw a debug box with rotation */ENGINE_API void DrawDebugBox(const UWorld* InWorld, FVector const& Center, FVector const& Box, const FQuat & Rotation, FColor const& Color, bool bPersistentLines = false, float LifeTime=-1.f, uint8 DepthPriority = 0);

第一个根据Box的尺寸绘制，第二个额外的可以按照一定的旋转绘制。

5.绘制球体

ENGINE_API void DrawDebugSphere(const UWorld* InWorld, FVector const& Center, float Radius, int32 Segments, FColor const& Color, bool bPersistentLines = false, float LifeTime=-1.f, uint8 DepthPriority = 0);

Segments控制球体的分段，越大越精细。

6.其他

还有很多不太常用的，可以绘制2D圆、圆柱、椎体、平截头体、胶囊等。这里只列出来，具体见DrawDebugHelpers.h

ENGINE_API void DrawDebugCoordinateSystem(const UWorld* InWorld, FVector const& AxisLoc, FRotator const& AxisRot, float Scale, bool bPersistentLines = false, float LifeTime=-1.f, uint8 DepthPriority = 0);/** Draw Debug Circle */ENGINE_API void DrawDebugCircle(const UWorld* InWorld, const FMatrix& TransformMatrix, float Radius, int32 Segments, const FColor& Color, bool bPersistentLines = false, float LifeTime=-1.f, uint8 DepthPriority = 0);/** Draw Debug 2D donut */ENGINE_API void DrawDebug2DDonut(const UWorld* InWorld, const FMatrix& TransformMatrix, float InnerRadius, float OuterRadius, int32 Segments, const FColor& Color, bool bPersistentLines = false, float LifeTime=-1.f, uint8 DepthPriority = 0);/** Draw a debug sphere */ENGINE_API void DrawDebugSphere(const UWorld* InWorld, FVector const& Center, float Radius, int32 Segments, FColor const& Color, bool bPersistentLines = false, float LifeTime=-1.f, uint8 DepthPriority = 0);/** Draw a debug cylinder */ENGINE_API void DrawDebugCylinder(const UWorld* InWorld, FVector const& Start, FVector const& End, float Radius, int32 Segments, FColor const& Color, bool bPersistentLines = false, float LifeTime=-1.f, uint8 DepthPriority = 0);ENGINE_API void DrawDebugCone(const UWorld* InWorld, FVector const& Origin, FVector const& Direction, float Length, float AngleWidth, float AngleHeight, int32 NumSides, FColor const& Color, bool bPersistentLines=false, float LifeTime=-1.f, uint8 DepthPriority = 0);/** Used by gameplay when defining a cone by a vertical and horizontal dot products. */ENGINE_API void DrawDebugAltCone(const UWorld* InWorld, FVector const& Origin, FRotator const& Rotation, float Length, float AngleWidth, float AngleHeight, FColor const& DrawColor, bool bPersistentLines=false, float LifeTime=-1.f, uint8 DepthPriority=0);ENGINE_API void DrawDebugString(const UWorld* InWorld, FVector const& TextLocation, const FString& Text, class AActor* TestBaseActor = NULL, FColor const& TextColor = FColor::White, float Duration = -1.000000);ENGINE_API void DrawDebugFrustum(const UWorld* InWorld, const FMatrix& FrustumToWorld, FColor const& Color, bool bPersistentLines = false, float LifeTime=-1.f, uint8 DepthPriority = 0);/** Draw a capsule using the LineBatcher */ENGINE_API void DrawDebugCapsule(const UWorld* InWorld, FVector const& Center, float HalfHeight, float Radius, const FQuat & Rotation, FColor const& Color, bool bPersistentLines=false, float LifeTime=-1.f, uint8 DepthPriority = 0);/** Draw a debug camera shape.  FOV is full angle in degrees. */ENGINE_API void DrawDebugCamera(const UWorld* InWorld, FVector const& Location, FRotator const& Rotation, float FOVDeg, float Scale=1.f, FColor const& Color=FColor::White, bool bPersistentLines=false, float LifeTime=-1.f, uint8 DepthPriority = 0);ENGINE_API void FlushDebugStrings(const UWorld* InWorld);ENGINE_API void DrawDebugSolidBox(const UWorld* InWorld, FVector const& Center, FVector const& Box, FColor const& Color, bool bPersistent=false, float LifeTime=-1.f, uint8 DepthPriority = 0);ENGINE_API void DrawDebugSolidBox(const UWorld* InWorld, FVector const& Center, FVector const& Extent, FQuat const& Rotation, FColor const& Color, bool bPersistent=false, float LifeTime=-1.f, uint8 DepthPriority = 0);ENGINE_API void DrawDebugMesh(const UWorld* InWorld, TArray<FVector> const& Verts, TArray<int32> const& Indices, FColor const& Color, bool bPersistent=false, float LifeTime=-1.f, uint8 DepthPriority = 0);ENGINE_API void DrawDebugSolidPlane(const UWorld* InWorld, FPlane const& P, FVector const& Loc, float Size, FColor const& Color, bool bPersistent=false, float LifeTime=-1, uint8 DepthPriority = 0);/* Draws a 2D Histogram of size 'DrawSize' based FDebugFloatHistory struct, using DrawTransform for the position in the world. */ENGINE_API void DrawDebugFloatHistory(UWorld const & WorldRef, FDebugFloatHistory const & FloatHistory, FTransform const & DrawTransform, FVector2D const & DrawSize, FColor const & DrawColor, bool const & bPersistent = false, float const & LifeTime = -1.f, uint8 const & DepthPriority = 0);/* Draws a 2D Histogram of size 'DrawSize' based FDebugFloatHistory struct, using DrawLocation for the location in the world, rotation will face camera of first player. */ENGINE_API void DrawDebugFloatHistory(UWorld const & WorldRef, FDebugFloatHistory const & FloatHistory, FVector const & DrawLocation, FVector2D const & DrawSize, FColor const & DrawColor, bool const & bPersistent = false, float const & LifeTime = -1.f, uint8 const & DepthPriority = 0);