RenderTexture, Textrue2D的一些用法

RenderTexture或Texture2D -> RenderTexture

public static RenderTexture TextureRenderToRT(Texture srcTex)
{
    var srcTempRT = RenderTexture.GetTemporary(srcTex.width, srcTex.height);
    Graphics.Blit(srcTex, srcTempRT); //贴图数据填充RT
    return srcTempRT;
}

 

active RenderTexture -> Texture2D

public static Texture2D CreateTexture2DByFullRT(RenderTexture srcRT, TextureFormat texFormat)
{
    var oldActiveRT = RenderTexture.active;
    RenderTexture.active = srcRT;

    var resultTex = new Texture2D(srcRT.width, srcRT.height, texFormat, false);
    resultTex.ReadPixels(new Rect(0, 0, srcRT.width, srcRT.height), 0, 0);
    resultTex.Apply();

    RenderTexture.active = oldActiveRT;
    return resultTex;
}


///从srcRT的rtArea区域生成Texture2D, rtArea的(x, y)为左上角
public static Texture2D CreateTexture2DByRTArea(RenderTexture srcRT, Rect rtArea, TextureFormat texFormat)
{
    var oldActiveRT = RenderTexture.active;
    RenderTexture.active = srcRT;

    //RenderTexture: (0, 0)为左上角, x向右为正, y向下为正.
    //Texture2D: (0, 0)为左下角, x向右为正, y向上为正.
    var resultTex = new Texture2D((int)rtArea.width, (int)rtArea.height, texFormat, false);
    resultTex.ReadPixels(rtArea, 0, 0); //读取RT的rtArea区域, 写到Texture2D的(0, 0)处
    resultTex.Apply();

    RenderTexture.active = oldActiveRT;
    return resultTex;
}

 

Camera -> RenderTexture

///相机画面渲染到RT上，如果RT宽高小于相机宽高，则只渲染相机画面的RT那部分大小
public static void CameraRenderToRT(Camera cam, RenderTexture tempRT)
{
    /*
    if (cameraList[i].targetTexture != null)
        Graphics.Blit(cameraList[i].targetTexture, tempRT); //RT不一样大小的情况没考虑
    */
    var oldTargetTexture = cam.targetTexture;
    cam.targetTexture = tempRT;
    cam.Render();
    cam.targetTexture = oldTargetTexture;
}

 

Texture2D裁剪

///裁剪贴图某块区域, texArea的(x, y)为左上角
public static Texture2D CropTexture2D(Texture2D srcTex, Rect texArea, TextureFormat texFormat)
{
    var srcTempRT = RenderTexture.GetTemporary(srcTex.width, srcTex.height);
    Graphics.Blit(srcTex, srcTempRT); //用贴图数据填充RT

    var oldActiveRT = RenderTexture.active;
    Graphics.SetRenderTarget(srcTempRT);

    var resultTex = new Texture2D((int)texArea.width, (int)texArea.height, texFormat, false);
    resultTex.ReadPixels(texArea, 0, 0); //读取RT的rtArea区域, 写到Texture2D的(0, 0)处
    resultTex.Apply();

    Graphics.SetRenderTarget(oldActiveRT);
    RenderTexture.ReleaseTemporary(srcTempRT);

    return resultTex;
}

法2

public static Texture2D CropTextrue2D2(Texture2D srcTex, Rect texArea, TextureFormat texFormat)
{
    var srcTempRT = RenderTexture.GetTemporary(srcTex.width, srcTex.height);

    var oldActiveRT = RenderTexture.active;
    Graphics.SetRenderTarget(srcTempRT);
    //用贴图数据填充RT
    {
        GL.LoadPixelMatrix(0, 1, 1, 0);
        var black = new Color(0, 0, 0, 0); //透明黑色
        GL.Clear(true, true, black);
        Graphics.DrawTexture(new Rect(0, 0, 1, 1), srcTex2d);
    }

    var resultTex = new Texture2D((int)texArea.width, (int)texArea.height, texFormat, false);
    resultTex.ReadPixels(texArea, 0, 0); //读取RT的rtArea区域, 写到Texture2D的(0, 0)处
    resultTex.Apply();

    Graphics.SetRenderTarget(oldActiveRT);
    RenderTexture.ReleaseTemporary(srcTempRT);

    return result;
}

 

设置Active RenderTexture的2种方式

第1种，上面的CreateTexture2DByFullRT就用了这种

public static void SetActiveRT1(RenderTexture rt)
{
    var oldActiveRT = RenderTexture.active;
    RenderTexture.active = rt;

    //使用active RT执行相关操作

    RenderTexture.active = oldActiveRT;
}

第2种，上面的CropTexture2D就用了这种

public static void SetActiveRT2(RenderTexture rt)
{
    var oldActiveRT = RenderTexture.active;
    Graphics.SetRenderTarget(srcTempRT);

    //使用active RT执行相关操作

    Graphics.SetRenderTarget(oldActiveRT);
}

SetRenderTarget(RenderTexture rt）和 RenderTexture.active = rt作用一样，都是把渲染的结果存到rt中，如果为null则输出到屏幕

///测试RenderTexture.active和Graphics.SetRenderTarget的作用是否一样
public static void test()
{
    var rt = RenderTexture.GetTemporary(128, 128);
    Graphics.SetRenderTarget(rt);
    if (RenderTexture.active == rt)
    {
        Debug.Log($"eq");
    }
}

 

 

【参考】

几个Graphics函数 - Tearix - 博客园 (cnblogs.com)