将3D点投影到2D屏幕坐标

根据3D Programming for Windows(Charles Petzold)第7章中的信息,我试图编写一个辅助函数,将Point3D投影到包含相应屏幕坐标(x,y)的标准2D点:

public Point Point3DToScreen2D(Point3D point3D,Viewport3D viewPort )
{
    double screenX = 0d, screenY = 0d;

    // Camera is defined in XAML as:
    //        
    //             
    //        

    PerspectiveCamera cam = viewPort.Camera as PerspectiveCamera;

    // Translate input point using camera position
    double inputX = point3D.X - cam.Position.X;
    double inputY = point3D.Y - cam.Position.Y;
    double inputZ = point3D.Z - cam.Position.Z;

    double aspectRatio = viewPort.ActualWidth / viewPort.ActualHeight;

    // Apply projection to X and Y
    screenX = inputX / (-inputZ * Math.Tan(cam.FieldOfView / 2));

    screenY = (inputY * aspectRatio) / (-inputZ * Math.Tan(cam.FieldOfView / 2));

    // Convert to screen coordinates
    screenX = screenX * viewPort.ActualWidth;

    screenY = screenY * viewPort.ActualHeight;


    // Additional, currently unused, projection scaling factors
    /*
    double xScale = 1 / Math.Tan(Math.PI * cam.FieldOfView / 360);
    double yScale = aspectRatio * xScale;

    double zFar = cam.FarPlaneDistance;
    double zNear = cam.NearPlaneDistance;

    double zScale = zFar == Double.PositiveInfinity ? -1 : zFar / (zNear - zFar);
    double zOffset = zNear * zScale;

    */

    return new Point(screenX, screenY);
}

然而,在测试时,此函数返回不正确的屏幕坐标(通过将2D鼠标坐标与简单的3D形状进行比较来检查).由于我缺乏3D编程经验,我很困惑为什么.

块注释部分包含可能必不可少的缩放计算,但是我不确定如何,并且本书继续使用XAML的MatrixCamera.最初,我只是希望得到一个基本的计算工作,无论它与矩阵相比效率如何.

任何人都可以建议需要添加或更改的内容吗？