c＃WPF 3D hitTest错误：不支持奇异的MatrixCamera

Question

这是我用来执行hitTest的代码：

RayHitTestResult hit = VisualTreeHelper.HitTest(
      App.MainWin.Viewport, location) as RayHitTestResult;

当摄像机的宽度较小（即对象较大）时，此代码有效。 当我将相机缩小（即对象变小）到某个点时，然后单击视口时，上面的代码显示错误，并且错误详细信息如下所示：

未处理System.NotSupportedException：不支持使用单个MatrixCamera进行命中测试。

我用谷歌搜索，没有人遇到此错误。 知道如何解决吗？ 谢谢！

我用来创建/更新MatrixCamera的代码：（它们受到Charles Petzold第7章“ Windows的3D编程：Windows Presentation Foundation的三维图形编程”一书中的示例的启发）

    //create a new camera, initialize it and attach it to the viewport.
    public void initCamera(Point3D position, Point3D AimPoint, 
                           Vector3D upDirection, double farDistance, 
                           double nearDistance, double Width)
    {
        this._Camera = new MatrixCamera();

        this.CameraAimPoint = (Vector3D)AimPoint;

        //check and adjust the camera depth if needed
        this.CameraZAxis = Point3D.Subtract(position, AimPoint); 

        this.CameraDepth = CameraZAxis.Length;

        this.CameraZAxis.Normalize();
        this.CameraPosition = this.CameraAimPoint + (this.CameraZAxis *  this.CameraDepth);

        this.CameraFarDistance = farDistance;
        this.CameraNearDistance = nearDistance;
        this.CameraWidth = Width;

        this.CameraXAxis = Vector3D.CrossProduct(upDirection, this.CameraZAxis);
        this.CameraXAxis.Normalize();

        this.CameraYAxis = Vector3D.CrossProduct(this.CameraZAxis, this.CameraXAxis);

        this._CameraViewMatrix = new Matrix3D();
        this._CameraViewMatrix.M14 = 0;
        this._CameraViewMatrix.M24 = 0;
        this._CameraViewMatrix.M34 = 0;
        this._CameraViewMatrix.M44 = 1;

        this.updateViewMatrix();

        this._CameraProjectMatrix = new Matrix3D();
        this._CameraProjectMatrix.M14 = 0;
        this._CameraProjectMatrix.M24 = 0;
        this._CameraProjectMatrix.M34 = 0;
        this._CameraProjectMatrix.M44 = 1;

        this.updateProjectionMatrix();

        this._Viewport.Camera = this._Camera;

    }

    private void updateViewMatrix(bool axisChanged=true)
    {
        if (axisChanged==true)
        {
            this._CameraViewMatrix.M11 = this.CameraXAxis.X;
            this._CameraViewMatrix.M12 = this.CameraYAxis.X;
            this._CameraViewMatrix.M13 = this.CameraZAxis.X;

            this._CameraViewMatrix.M21 = this.CameraXAxis.Y;
            this._CameraViewMatrix.M22 = this.CameraYAxis.Y;
            this._CameraViewMatrix.M23 = this.CameraZAxis.Y;

            this._CameraViewMatrix.M31 = this.CameraXAxis.Z;
            this._CameraViewMatrix.M32 = this.CameraYAxis.Z;
            this._CameraViewMatrix.M33 = this.CameraZAxis.Z;
        }

        this._CameraViewMatrix.OffsetX = -Vector3D.DotProduct(this.CameraXAxis, this.CameraPosition);
        this._CameraViewMatrix.OffsetY = -Vector3D.DotProduct(this.CameraYAxis, this.CameraPosition);
        this._CameraViewMatrix.OffsetZ = -Vector3D.DotProduct(this.CameraZAxis, this.CameraPosition);

        this._Camera.ViewMatrix = this._CameraViewMatrix;
        this._3DTo2DTransformMatrixIsDefined = false;

        AfterDraw();
    }

    //
    private void updateProjectionMatrix() {
        double ScaleX = 2 / CameraWidth;
        double ScaleY = _Viewport.ActualWidth / _Viewport.ActualHeight * ScaleX;
        double ScaleZ = 1 / (CameraNearDistance - CameraFarDistance);
        double zOffset = CameraNearDistance * ScaleZ;

        _CameraProjectMatrix.M11 = ScaleX;
        _CameraProjectMatrix.M22 = ScaleY;
        _CameraProjectMatrix.M33 = ScaleZ;
        _CameraProjectMatrix.OffsetZ = zOffset;

        _Camera.ProjectionMatrix = _CameraProjectMatrix;
        _3DTo2DTransformMatrixIsDefined = false;

        _PixelToWorldUnit = CameraWidth / _Viewport.ActualWidth;

        AfterDraw();

    }

执行相机缩放的代码：

    private void _cameraZoomToScale(double width)
    {
        if (width< 1) width = 1;
        this.CameraWidth = width;
        updateProjectionMatrix();

    }

Answer 1

很明显，您正在缩放的​​范围超出了MatrixCamera支持的范围。 找出此异常发生在什么缩放级别，并防止用户走得太远。 if (scale < 1) scale = 1;您可能已经尝试这样做if (scale < 1) scale = 1; 但是在发布的代码中似乎没有使用scale 。