Unity RenderTexture读取越界及截图显示异常问题求助

问题分析 #

你遇到的Attempting to ReadPixels outside of RenderTexture bounds错误，根源是混淆了屏幕坐标和RenderTexture内部坐标：你用ViewportToScreenPoint获取的是小地图在屏幕上的位置（屏幕坐标），但读取RenderTexture像素时需要用它自身的内部坐标，两者范围完全不匹配，导致读取区域超出RenderTexture的768×432边界。

另外你提到设置RoI为(0,0,targetTextureWidth,targetTextureHeight)后截图不符合预期，是因为之前通过屏幕坐标计算的targetTextureWidth/Height可能存在误差，且没有正确处理全屏显示的绘制逻辑。

修正方案 #

核心思路 #

1. 直接为turretCamera创建固定尺寸（768×432）的RenderTexture，避免通过屏幕坐标计算带来的误差；
2. 读取RenderTexture像素时，直接读取其完整区域（内部坐标从(0,0)到自身宽高）；
3. 全屏显示时，将截取的纹理绘制到整个屏幕区域。

修正后代码 #

using UnityEngine;
// 请确保引入Model和Worker相关命名空间

public class MinimapCapture : MonoBehaviour
{
    public Camera turretCamera;
    public ModelAsset modelAsset;
    
    private Worker worker;
    private RenderTexture renderTexture;
    private RenderTexture tmpRenderTexture;
    private Texture2D minimapTexture;
    
    // 小地图固定尺寸
    private const int MINIMAP_WIDTH = 768;
    private const int MINIMAP_HEIGHT = 432;

    void Start()
    {
        // 初始化模型与Worker
        Model model = ModelLoader.Load(modelAsset);
        worker = WorkerFactory.CreateWorker(WorkerFactory.Type.ComputePrecompiled, model);

        // 创建匹配小地图尺寸的RenderTexture
        renderTexture = new RenderTexture(MINIMAP_WIDTH, MINIMAP_HEIGHT, 24);
        // 保存原渲染目标，退出时恢复
        tmpRenderTexture = turretCamera.targetTexture;
        turretCamera.targetTexture = renderTexture;
    }

    // 每帧末尾更新截图，确保turretCamera已完成渲染
    private void LateUpdate()
    {
        UpdateMinimapScreenshot();
    }

    private void UpdateMinimapScreenshot()
    {
        if (renderTexture == null) return;

        // 初始化或更新Texture2D尺寸
        if (minimapTexture == null || 
            minimapTexture.width != renderTexture.width || 
            minimapTexture.height != renderTexture.height)
        {
            minimapTexture = new Texture2D(renderTexture.width, renderTexture.height, TextureFormat.RGB24, false);
        }

        // 读取RenderTexture完整像素
        RenderTexture.active = renderTexture;
        minimapTexture.ReadPixels(new Rect(0, 0, renderTexture.width, renderTexture.height), 0, 0);
        minimapTexture.Apply();
        RenderTexture.active = null;
    }

    private void OnGUI()
    {
        if (minimapTexture == null) return;

        // 全屏绘制小地图纹理
        GUI.DrawTexture(new Rect(0, 0, Screen.width, Screen.height), minimapTexture);
    }

    // 清理资源，避免内存泄漏
    private void OnDestroy()
    {
        if (turretCamera != null && tmpRenderTexture != null)
        {
            turretCamera.targetTexture = tmpRenderTexture;
        }
        if (renderTexture != null)
        {
            renderTexture.Release();
            Destroy(renderTexture);
        }
        if (minimapTexture != null)
        {
            Destroy(minimapTexture);
        }
        worker?.Dispose();
    }
}

关键说明 #

• RenderTexture坐标逻辑：Unity纹理的原点在左下角，所以读取完整区域用new Rect(0, 0, renderTexture.width, renderTexture.height)即可，无需涉及屏幕坐标；
• 渲染时机：用LateUpdate更新截图，确保turretCamera在当前帧已经完成渲染，避免截取到空白或旧画面；
• 资源清理：在OnDestroy中恢复原渲染目标、释放RenderTexture和Texture2D，防止内存泄漏。

内容的提问来源于stack exchange，提问作者Alfonso