Unity intercepts 3D images and the implementation of picture-in-picture PIP

1 前言

在Unityto get some3DA screenshot of the game object,是比较容易的,本文来讨论一下.

Implemented core program,是新建一个Camera,Camera指向目标对象.Camera有个参数是TargetTexture,Called the target render texture,Extract the pixels of this texture,生成图片.

来看一下Camera的属性：

一般情况下,The camera renders directly to the screen,即,当 targetTexture 为 null 时,The camera renders to the screen.But if create one RenderTexture 对象, Set it to on the camera targetTexture,The camera will render to it 该纹理.when rendering to a texture,The camera always renders into the entire texture. There is one离屏渲染FBO的味道了^^

再补充一下RenderTexture的知识.RenderTexture即,渲染纹理,Refers to a texture that can be rendered dynamically.

They can be used to implement image-based rendering effects、动态阴影、 投影器、Reflection or surveillance cameras.
A typical use of a render texture is to set it to 摄像机的“目标纹理”属性 (Camera.targetTexture),This will render the camera to the texture, instead of rendering to the screen.

2 具体实现

背景：There is a simple one as follows3D世界,包括一个Cube正方体,一个Plane Green tablet,一个PlaneWhite tablet.
目标：把CubeTaken together with the green plate.

2.1 New off-screen renderingCamera

新建一个Camera,视锥ProjectionSet to orthographic projectionOrthographic,位置放在3Dbehind the object,Make it shine on the target GameObject,具体如下：

选中Camera对象,There will be a small window,arrow in the picture,可以看到CameraThe resulting actual view,Convenient for your debugging location,大小.

如果要调整Camerarange of the viewing cone,parameters can be modifiedSize.

接下来,就可以写代码,Go take a screenshot.

2.2 代码实现

具体如下：

using Assets.Scripts;
using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class Get3DImage : MonoBehaviour
{
    
    private RenderTexture shortcutRenderTexture;
    private Camera cutImageCamera;
    // Start is called before the first frame update
    void Start()
    {
    
        cutImageCamera = GameObject.Find("CutImageCamera").GetComponent<Camera>();
        init();
    }

    // Update is called once per frame
    void Update()
    {
    
        
    }

    private void init()
    {
    
        shortcutRenderTexture = RenderTexture.GetTemporary(600, 600, 16, RenderTextureFormat.Default, RenderTextureReadWrite.Linear);
        shortcutRenderTexture.enableRandomWrite = true;
        cutImageCamera.targetTexture = shortcutRenderTexture;
    }

    public void StartCutImage()
    {
    
        // Create a new Texture2D and read the RenderTexture image into it
        RenderTexture.active = shortcutRenderTexture;
        Texture2D drawTexture2D = new Texture2D(shortcutRenderTexture.width, shortcutRenderTexture.height, TextureFormat.RGB24, false);
        drawTexture2D.ReadPixels(new Rect(0, 0, shortcutRenderTexture.width, shortcutRenderTexture.height), 0, 0);
        drawTexture2D.Apply();

        TextureUtils.saveTextureToFile(drawTexture2D, "SaveShortcut");
    }

    private void OnDestroy()
    {
    
        RenderTexture.ReleaseTemporary(shortcutRenderTexture);
    }
}

核心代码

RenderTexture.active = shortcutRenderTexture;

The core code above,表示设置当前的activeRenderTexture为 Camera所指向的RenderTexture（There may be more than one in the same game sceneRenderTexture）.此时可以新建一个Texture2D,调用ReadPixels,The active state is readRenderTexture的内容.

接下来就简单了,把Texture2D保存即可.代码如下：

using System.IO;
using UnityEngine;

namespace Assets.Scripts
{
    
    class TextureUtils
    {
    
        public static Texture2D DeCompress(Texture2D source)
        {
    
            RenderTexture renderTex = RenderTexture.GetTemporary(
                        source.width,
                        source.height,
                        0,
                        RenderTextureFormat.Default,
                        RenderTextureReadWrite.Linear);

            Graphics.Blit(source, renderTex);
            RenderTexture previous = RenderTexture.active;
            RenderTexture.active = renderTex;
            Texture2D readableText = new Texture2D(source.width, source.height);
            readableText.ReadPixels(new Rect(0, 0, renderTex.width, renderTex.height), 0, 0);
            readableText.Apply();
            RenderTexture.active = previous;
            RenderTexture.ReleaseTemporary(renderTex);
            return readableText;
        }


        public static string saveTextureToFile(Texture2D texture, string fileName)
        {
    
            if (texture == null)
            {
    
                return "";
            }

            byte[] bytes = TextureUtils.DeCompress(texture).EncodeToPNG();
            string filename = Application.persistentDataPath + "/" + fileName + ".png";
            Debug.Log("DrawManager::saveTextureToFile = " + filename);
            File.WriteAllBytes(filename, bytes);
            return filename;
        }

    }
}

3 用RenderTexture实现画中画

本文使用到了RenderTexture,And it is created dynamically by code.We can also create in the menu,You can even do a picture-in-picturePIP的功能,比较有意思,顺着思路,Let's talk about the implementation of picture-in-picture.

3.1 建RenderTexture

在Assets目录下,右键,Create – RenderTexture,新建一个渲染纹理.
然后,把SizeThe parameters are set to be the same as the screen width and height,例如1920x1080.

3.2 build material

接着,右键,Create – Material,新建一个材质.Shader选为Unlit/Texture.然后,Right arrow below,The texture used by the material,选择为上面新建的RenderTexture.

There is material,It can be used in game scenes！

3.3 建Image作为PIP窗口

新建一个2D Image,然后把Image的材质,设置为3.2The material that was built.

好了,运行起来,效果如下：

最后,上代码：
TestGet3DImage