利用C#实现绘制出地球旋转效果

private MeshGeometry3D SetEarth(int numx, int numz, double r=3)
{
    MeshGeometry3D mesh = new MeshGeometry3D();

    double dTh = 2 * Math.PI / numx;
    double dPhi = Math.PI / numz;

    double X(double th, double phi) => r * Math.Sin(phi) * Math.Cos(th);
    double Y(double th, double phi) => r * Math.Sin(phi) * Math.Sin(th);
    double Z(double phi) => r * Math.Cos(phi);

    // Make the points.
    for (int i = 0; i <= numx; i++)
        for (int j = 0; j <= numz; j++)
        {
            var th = i * dTh;
            var phi = j * dPhi;
            mesh.Positions.Add(new Point3D(X(th, phi), Y(th, phi), Z(phi)));
            mesh.TextureCoordinates.Add(new Point(th, phi));
        }

    // 生成三角形
    for (int i = 0; i < numx; i++)
        for (int j = 0; j < numz; j++)
        {
            int i1 = i * (numz + 1) + j;
            int i2 = i1 + 1;
            int i3 = i2 + (numz + 1);
            int i4 = i3 - 1;
            mesh.TriangleIndices.Add(i1);
            mesh.TriangleIndices.Add(i2);
            mesh.TriangleIndices.Add(i3);

            mesh.TriangleIndices.Add(i1);
            mesh.TriangleIndices.Add(i3);
            mesh.TriangleIndices.Add(i4);
        }
    return mesh;
}

public MainWindow()
{
    InitializeComponent();
    initialize3D();
    timer.Interval = TimeSpan.FromMilliseconds(5);
    timer.Tick += Timer_Tick;
    timer.Start();
}

double thAngle = 0;
private void Timer_Tick(object? sender, EventArgs e)
{
    thAngle = thAngle > Math.PI ? 0 : thAngle + 0.1;
    Rotation3D rotation = new AxisAngleRotation3D(new Vector3D(0,0,1), thAngle);
    var rot = new RotateTransform3D(rotation, new Point3D(0,0,0));
    Point3D[] pts = mesh.Positions.ToArray();
    rot.Transform(pts);
    mesh.Positions = new Point3DCollection(pts);
}