Unity保存RenderTarget

使用Unity产出一些美术资产时，经常需要保存某个RenderTarget，最近发现用ReadPixels进行保存时，精度很差，只有8 bits，最后成功搞定了保存32 bits RenderTarget的方法，在此记录一下

屏幕截图

如果想要保存当前屏幕的渲染结果，可以直接调用

ScreenCapture.CaptureScreenshot(pngPath);

保存相机的RT

public Camera renderCamera;

void saveColor()
{
    RenderTexture activeRenderTexture = RenderTexture.active;
    RenderTexture cameraRenderTexture = new RenderTexture(renderCamera.pixelWidth, renderCamera.pixelHeight, 24);
    renderCamera.targetTexture = cameraRenderTexture;
    renderCamera.Render();
    RenderTexture.active = cameraRenderTexture;

    Texture2D cameraImage = new Texture2D(renderCamera.pixelWidth, renderCamera.pixelHeight, TextureFormat.RGBAFloat, false);
    cameraImage.ReadPixels(new Rect(0, 0, cameraRenderTexture.width, cameraRenderTexture.height), 0, 0);
    cameraImage.Apply();

    Color[] colors = cameraImage.GetPixels();
    byte[] cameraImageBytes = cameraImage.EncodeToTGA();
    File.WriteAllBytes(Path.Combine(outputPath, "cameraImage.tga"), cameraImageBytes);

}

保存深度

public RenderTexture depthTarget;

void Start()
{
    depthTarget = new RenderTexture(1024, 1024, 0, RenderTextureFormat.RHalf)
    {
        autoGenerateMips = false,
        useMipMap = false,
        filterMode = FilterMode.Point
    };
    depthTarget.Create();
    Camera.main.depthTextureMode |= DepthTextureMode.Depth;
}

void SaveDepth()
{
    // 创建一个临时RT
    RenderTexture depthRT = RenderTexture.GetTemporary(Screen.width, Screen.height, 0, depthTarget.format);
    depthRT.filterMode = FilterMode.Point;
    // 将GPU的深度贴图Blit到临时RT上
    Graphics.Blit(Shader.GetGlobalTexture("_CameraDepthTexture"), depthRT);
	// 将临时RT的像素保存到Color数组
    Texture2D depthTexture = new Texture2D(depthRT.width, depthRT.height, TextureFormat.RFloat, false);
    RenderTexture.active = depthRT;
    depthTexture.ReadPixels(new Rect(0, 0, depthRT.width, depthRT.height), 0, 0);
    depthTexture.Apply();
    Color[] pixels = depthTexture.GetPixels();
    RenderTexture.active = null;
    // 编码、写贴图
    byte[] bytes = depthTexture.EncodeToPNG();
    string filename = Path.Combine(outputPath, "depth.png");
	File.WriteAllBytes(filename, bytes);
}

更高精度的RT

我发现在保存相机RT时，每个通道的精度仅仅是8 bits，将这些通道乘以255.0f，就非常接近整数了

这其实是因为cameraRenderTexture的默认格式是ARGB32，每个通道仅8 bits，我只需要在其创建时设置一个更高精度的格式，比如ARGBFloat，每个通道32 bits，精度就大大提高了

RenderTexture cameraRenderTexture = new RenderTexture(renderCamera.pixelWidth, 
renderCamera.pixelHeight, 24, 
+RenderTextureFormat.ARGBFloat
);