基于UE4+ OpenCV 的混合现实 (webCamera, mix-reality, blue screen matting)

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总体效果

类似混合现实，实现展示玩家玩的VR游戏的实况

基本思想

利用openCV 插件，通过摄像头获取到玩家在蓝幕中玩游戏的场景，再使用蓝幕技术，对图像做处理，获取玩家的图像；最后和游戏场景进行叠加。

具体实现( UE 4.12, Opencv 2.4.13)

1, 在UE4 中打开 vs，添加一个class，继承 Actor， WebCameraReader

2. UE4 中使用OpenCV 插件

方法一：使用项目的dll 包含，即在项目中包含 OpenCV 文件中的 include，然后在dll 中包含 \opencv\build\x64\vc12\lib (64位系统);

方法二：把openCV的dll，做成一个插件调用；具体步骤整理下插件的写法：① 在项目文件中，添加Plugins 文件夹，之后在Plugins 文件夹里面再创建一个插件的文件夹，比如 Plugins\CoolPlugin; 下面是CoolPlugin 的一些文件夹

uplugin 文件中，是需要编辑一些插件的信息，这些后面会显示在UE编辑器的插件信息中，如下所示，可以有一些关于插件的具体信息

{"FileVersion": 3,"Version": 1,"VersionName": "1.0","FriendlyName": "Webcamera","Description": "Adds web camera support","Category": "WebcamReader","CreatedBy": "Milen","CreatedByURL": "http://blog.csdn.net/himilong/article/details/52829231","DocsURL": "http://blog.csdn.net/himilong/article/details/52829231","MarketplaceURL": "","SupportURL": "http://blog.csdn.net/himilong/article/details/52829231","Modules": [{"Name": "CoolPlugin","Type": "Editor","LoadingPhase": "Default"}],"EnabledByDefault": false,"CanContainContent": false,"IsBetaVersion": false,"Installed": false}

在文件夹，ThirdParty 创建OpenCV ，里面我们可以加入需要用到的include(OpenCV\Includes) 文件以及 dll, lib文件（OpenCV\Libraries）.

这些准备工作做好之后，就可以在代码中加载需要用到的lib 文件, dll 文件了。在 CoolPlugin\Source\CoolPlugin 中，创建CoolPlugin.Buid.cs 文件

using UnrealBuildTool;using System.IO;public class CoolPlugin : ModuleRules{    public CoolPlugin(TargetInfo target)    {        PrivateDependencyModuleNames.AddRange(            new string[] {                "Engine",                "UnrealEd",                "InputCore",                "Core",                "Slate",                "SlateCore",                "EditorStyle",                "CoreUObject",                "CoolPlugin"   // add plugin file name             });        PrivateIncludePaths.AddRange(new[] { "CoolPlugin/Private" });          LoadOpenCV(target);  //load dll or  lib files    }    //LoadOpenCV(Target);    private string ModulePath    {        get        {            RulesAssembly r;            FileReference CheckProjectFile;            UProjectInfo.TryGetProjectForTarget("CoolProject", out CheckProjectFile);            r = RulesCompiler.CreateProjectRulesAssembly(CheckProjectFile);            FileReference f = r.GetModuleFileName(this.GetType().Name);            return Path.GetDirectoryName(f.CanonicalName);        }        //get { return Path.GetDirectoryName(RulesCompiler.GetModuleFilename(this.GetType().Name)); }    }    private string ThirdPartyPath    {        get { return Path.GetFullPath(Path.Combine(ModulePath, "../../ThirdParty/")); }    }    public bool LoadOpenCV(TargetInfo Target)    {        bool isLibrarySupported = false;        // Create OpenCV Path         string OpenCVPath = Path.Combine(ThirdPartyPath, "OpenCV");        // Get Library Path         string LibPath = "";        bool isdebug = Target.Configuration == UnrealTargetConfiguration.Debug && BuildConfiguration.bDebugBuildsActuallyUseDebugCRT;        if (Target.Platform == UnrealTargetPlatform.Win64)        {            LibPath = Path.Combine(OpenCVPath, "Libraries", "Win64");            isLibrarySupported = true;        }        else if (Target.Platform == UnrealTargetPlatform.Win32)        {            LibPath = Path.Combine(OpenCVPath, "Libraries", "Win32");            isLibrarySupported = true;        }        else        {            string Err = string.Format("{0} dedicated server is made to depend on {1}. We want to avoid this, please correct module dependencies.", Target.Platform.ToString(), this.ToString()); System.Console.WriteLine(Err);        }       // PublicIncludePaths.AddRange(new string[] { "<Modulename>/Public", "<Modulename>/Classes" });        //PublicIncludePaths.AddRange(new string[] { Path.Combine(OpenCVPath, "Includes") });        if (isLibrarySupported)        {            //Add Include path             PublicIncludePaths.AddRange(new string[] { Path.Combine(OpenCVPath, "Includes") });            // Add Library Path             PublicLibraryPaths.Add(LibPath);              if (!isdebug)            {                PublicAdditionalLibraries.Add("opencv_imgproc2413.lib");                //Add Dynamic Libraries (Debug Version)                PublicDelayLoadDLLs.Add("opencv_imgproc2413.dll");                PublicAdditionalLibraries.Add("opencv_core2413.lib");                //Add Dynamic Libraries (Debug Version)                PublicDelayLoadDLLs.Add("opencv_core2413.dll");                PublicAdditionalLibraries.Add("opencv_highgui2413.lib");                //Add Dynamic Libraries (Debug Version)                PublicDelayLoadDLLs.Add("opencv_highgui2413.dll");            }            else            {                //Add Static Libraries (Debug Version)                //PublicAdditionalLibraries.Add("opencv_ts300d.lib");                PublicAdditionalLibraries.Add("opencv_imgproc2413d.lib");                //Add Dynamic Libraries (Debug Version)                PublicDelayLoadDLLs.Add("opencv_imgproc2413d.dll");                PublicAdditionalLibraries.Add("opencv_core2413d.lib");                //Add Dynamic Libraries (Debug Version)                PublicDelayLoadDLLs.Add("opencv_core2413d.dll");                PublicAdditionalLibraries.Add("opencv_highgui2413d.lib");                //Add Dynamic Libraries (Debug Version)                PublicDelayLoadDLLs.Add("opencv_highgui2413d.dll");            }        }        Definitions.Add(string.Format("WITH_OPENCV_BINDING={0}", isLibrarySupported ? 1 : 0));        return isLibrarySupported;    }}

最后，在CoolPlugin\Source\CoolPlugin\Private 中添加插件本身需要用到的代码。

3. 在webcamReader.h 中包含使用到的OpenCV 中文件

#include "opencv2/core.hpp"#include "opencv2/highgui.hpp"#include "opencv2/imgproc.hpp"#include "opencv2/video.hpp"

定义后面需要用到的几个主要用到的函数，onNextVideoFrame() 是在每获取到新的一帧图像之后的event， videoTextur 用来保存每次读取到的帧。 update 顾名思义就是不停的读图像，更新帧。

// Fill out your copyright notice in the Description page of Project Settings.UCLASS()class MYPROJECT_API AWebcamReader : public AActor{GENERATED_BODY()public:// Sets default values for this actor's propertiesAWebcamReader();// deallocates memory for the opencv fields~AWebcamReader();// Called when the game starts or when spawnedvirtual void BeginPlay() override;// Called every framevirtual void Tick( float DeltaSeconds ) override;// The device ID opened by the Video StreamUPROPERTY(BlueprintReadWrite, EditAnywhere, Category = Webcam)int32 CameraID ;//UPROPERTY(interp, Category = CameraSettings, meta = (ShowOnlyInnerProperties)) //struct FPostProcessSettings PostProcessSettings;UPROPERTY(interp, BlueprintReadWrite, Category = CameraSettings)//, meta = (ShowOnlyInnerProperties)) struct FPostProcessSettings PostProcessSettings;// If the webcam images should be resized every frameUPROPERTY(BlueprintReadWrite, EditAnywhere, Category = Webcam)bool ShouldResize;// The targeted resize width and height (width, height)UPROPERTY(BlueprintReadWrite, EditAnywhere, Category = Webcam)FVector2D ResizeDeminsions;// The rate at which the color data array and video texture is updated (in frames per second)UPROPERTY(BlueprintReadWrite, EditAnywhere, Category = Webcam)float RefreshRate;// The refresh timerUPROPERTY(BlueprintReadWrite, Category = Webcam)float RefreshTimer;// Blueprint Event called every time the video frame is updatedUFUNCTION(BlueprintNativeEvent, Category = Webcam)void OnNextVideoFrame();// OpenCV fieldscv::Mat* frame;cv::VideoCapture* stream;cv::Size* size;// OpenCV prototypesvoid UpdateFrame();void UpdateTexture();// If the stream has succesfully opened yetUPROPERTY(BlueprintReadWrite, Category = Webcam)bool isStreamOpen;// The videos width and height (width, height)UPROPERTY(BlueprintReadWrite, Category = Webcam)FVector2D VideoSize;// The current video frame's corresponding textureUPROPERTY(BlueprintReadWrite, Category = Webcam)UTexture2D* VideoTexture;// The current data arrayUPROPERTY(BlueprintReadWrite, Category = Webcam)TArray<FColor> Data;protected:// Use this function to update the texture rects you want to change:// NOTE: There is a method called UpdateTextureRegions in UTexture2D but it is compiled WITH_EDITOR and is not marked as ENGINE_API so it cannot be linked// from plugins.// FROM: https://wiki.unrealengine.com/Dynamic_Texturesvoid UpdateTextureRegions(UTexture2D* Texture, int32 MipIndex, uint32 NumRegions, FUpdateTextureRegion2D* Regions, uint32 SrcPitch, uint32 SrcBpp, uint8* SrcData, bool bFreeData);// Pointer to update texture region 2D structFUpdateTextureRegion2D* VideoUpdateTextureRegion;};

4. cpp 文件，首先初始化这个类，包含摄像机的ID，更新频率以及程序用到的变量等

AWebcamReader::AWebcamReader(){ // Set this actor to call Tick() every frame.  You can turn this off to improve performance if you don't need it.PrimaryActorTick.bCanEverTick = true;// Initialize OpenCV and webcam propertiesCameraID = 0;RefreshRate = 15;isStreamOpen = false;VideoSize = FVector2D(0, 0);ShouldResize = false;ResizeDeminsions = FVector2D(320, 240);stream = new cv::VideoCapture();frame = new cv::Mat();RefreshTimer = 1000000.0f;}

在begin 中，打开摄像机，读取第一帧

void AWebcamReader::BeginPlay(){Super::BeginPlay();stream->open(CameraID);if (stream->isOpened()){//Initialize streamisStreamOpen = true;UpdateFrame();VideoSize = FVector2D(frame->cols, frame->rows);size = new cv::Size(ResizeDeminsions.X, ResizeDeminsions.Y);VideoTexture = UTexture2D::CreateTransient(VideoSize.X, VideoSize.Y);VideoTexture->UpdateResource();VideoUpdateTextureRegion = new FUpdateTextureRegion2D(0, 0, 0, 0, VideoSize.X, VideoSize.Y);//Initialize data arrayData.Init(FColor(0, 0, 0, 255), VideoSize.X * VideoSize.Y);}}

tick() 函数中进行更新，并不断的调用 onNextVideoFrame()，这个在后面的蓝图中，需要用到。 updateframe() 读数据，updatetexture()更新videotexture。

// Called every framevoid AWebcamReader::Tick( float DeltaTime ){Super::Tick( DeltaTime );RefreshTimer += DeltaTime;if (isStreamOpen && RefreshTimer >= 1.0f / RefreshRate){RefreshTimer -= 1.0f / RefreshRate;UpdateFrame();UpdateTexture();OnNextVideoFrame();}}

5, 新建一个material，作为后期渲染的材质(material domain 设置为 post process)，按如下蓝图，实现对人物意外的背景色的剔除。其中需要注意创建的texture parameter，这个在后面的作为 settextureparametervalue 的 paramer name. 如下蓝图的主要思想就是对pix 的RGB 进行分流，背景色使用sceneTexture, 而人物保持不变. 此处背景是绿色，而绿色，人物的皮肤颜色，或者白色衣服等玩家可能出现颜色的G分量都比较大()，综合就采用相加的方法，作为if判断的A变量。背景色 R+ G 比较小，而人物的颜色比较大。从而区分

6. 编译上面的类之后，回到UE4 的编辑中，新建一个 webCamReader 的蓝图类

7, 使用上面的材质，创建 dynamic material instance，然后动态改变其 parameter value。post process 是添加的 component，用于后期剔除人物背景。

set unbound 勾选，可以实现全屏的后期效果。这些可以在unreal 文档中查询到，不再叙述。

8，点击 play 就可以实现本文刚开始的功能了！

Plugin Download:

http://download.csdn.net/detail/himilong/9681340

Reference :

uploadvr.com/epic-unreal-engine-4-mixed-reality-support/

opencv-srf.blogspot.com/2013/05/installing-configuring-opencv-with-vs.html

wiki.unrealengine.com/Integrating_OpenCV_Into_Unreal_Engine_4

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