[UE4][C++]调整分屏模式下（本地多玩家）视口的显示位置和区域

一、分屏模式设置

          在UE4中，多个玩家共用一个显示器就可以启用分屏模式，按玩家人数（最大四人）将屏幕均匀分割，显示不同玩家的视角，开发者可以在编辑器里设置分割类型（水平或者垂直），这个分割是采用UV坐标的方式。

（进入项目设置--项目--地图和模式--本地多人）

调整Player的摄像机的宽高比，可以调整显示画面的大小比例

二、分屏位置构造

分屏源代码位于：\Runtime\Engine\Private\GameViewportClient.cpp 

        其位置位于构造函数中  （部分源码截图），它定义了从1个玩家到4个玩家的的屏幕排列顺序和区域。

分屏方式定义如下

/**
 * Enum of the different splitscreen types
 */
namespace ESplitScreenType
{
	enum Type
	{
		// No split
		None,
		// 2 player horizontal split
		TwoPlayer_Horizontal,
		// 2 player vertical split
		TwoPlayer_Vertical,
		// 3 Player split with 1 player on top and 2 on bottom
		ThreePlayer_FavorTop,
		// 3 Player split with 1 player on bottom and 2 on top
		ThreePlayer_FavorBottom,
		//3 Player vertical split
		ThreePlayer_Vertical,
		//3 Player horizontal split
		ThreePlayer_Horizontal,
		// 4 Player grid split
		FourPlayer_Grid,
		// 4 Player vertical split
		FourPlayer_Vertical,
		// 4 Player horizontal split
		FourPlayer_Horizontal,

		SplitTypeCount
	};

	// Deprecated old FourPlayer grid enum value
	UE_DEPRECATED(4.21, "FourPlayer is now FourPlayer_Grid")
	const Type FourPlayer = FourPlayer_Grid;
}

 屏幕排列位置和区域定义如下

/** Structure to store splitscreen data. */
struct FPerPlayerSplitscreenData
{
	float SizeX;
	float SizeY;
	float OriginX;
	float OriginY;


	FPerPlayerSplitscreenData()
		: SizeX(0)
		, SizeY(0)
		, OriginX(0)
		, OriginY(0)
	{
	}

	FPerPlayerSplitscreenData(float NewSizeX, float NewSizeY, float NewOriginX, float NewOriginY)
		: SizeX(NewSizeX)
		, SizeY(NewSizeY)
		, OriginX(NewOriginX)
		, OriginY(NewOriginY)
	{
	}

};

 因此只要我们去修改结构体里的数据就可以做到调节位置和区域

三、分屏位置调节

为了能在蓝图里动态修改我同样也构建了相同的结构体

USTRUCT(BlueprintType)
struct FSplitData
{
	GENERATED_USTRUCT_BODY()

	UPROPERTY(EditAnywhere)
		float SizeX;
	UPROPERTY(EditAnywhere)
		float SizeY;
	UPROPERTY(EditAnywhere)
		float OriginX;
	UPROPERTY(EditAnywhere)
		float OriginY;
	
	FSplitData()
	{
		SizeX = 0;
		SizeY = 0;
		OriginX = 0;
		OriginY = 0;
	}

	FSplitData(float x,float y,float sizex,float sizey):
		OriginX(x),
		OriginY(y),
		SizeX(sizex),
		SizeY(sizey)
	{

	}
};

我在gamemode里创建代码，在地图蓝图中去调用代码就可以改变分屏位置

void ABloodGameModeBase::SplitScreen(TArray<FSplitData> DataArray)
{
	//4个player
	if (GEngine && GEngine->GameViewport)
	{
		if (DataArray.Num() == 4)
		{
			for (int i = 0; i < 4; i++)
			{
				GEngine->GameViewport->SplitscreenInfo[ESplitScreenType::FourPlayer_Vertical].PlayerData[i].OriginX = DataArray[i].OriginX;
				GEngine->GameViewport->SplitscreenInfo[ESplitScreenType::FourPlayer_Vertical].PlayerData[i].OriginY = DataArray[i].OriginY;
				GEngine->GameViewport->SplitscreenInfo[ESplitScreenType::FourPlayer_Vertical].PlayerData[i].SizeX = DataArray[i].SizeX;
				GEngine->GameViewport->SplitscreenInfo[ESplitScreenType::FourPlayer_Vertical].PlayerData[i].SizeY = DataArray[i].SizeY;
			}
		}
		//log
		GEngine->AddOnScreenDebugMessage(-1, 5.f, FColor::Red, TEXT("SplitScreen"));
	}
}