public class Particle
 {
  public Point3D Position;//位置
  public double Size;//尺寸
  public int XIndex;//X位置標識
  public int YIndex;//Y位置標識
 }

public class ParticleSystem
 {
  private readonly List<Particle> _particleList;
  private readonly GeometryModel3D _particleModel;
  private readonly int SEPARATION = 100;
 
  public ParticleSystem(int amountX, int amountY, Color color, int Size)
  {
   XParticleCount = amountX;
   YParticleCount = amountY;
 
   _particleList = new List<Particle>();
 
   _particleModel = new GeometryModel3D { Geometry = new MeshGeometry3D() };
 
   var e = new Ellipse
   {
    Width = Size,
    Height = Size
   };
   var b = new RadialGradientBrush();
   b.GradientStops.Add(new GradientStop(Color.FromArgb(0xFF, color.R, color.G, color.B), 0.25));
   b.GradientStops.Add(new GradientStop(Color.FromArgb(0x00, color.R, color.G, color.B), 1.0));
   e.Fill = b;
   e.Measure(new Size(Size, Size));
   e.Arrange(new Rect(0, 0, Size, Size));
 
   Brush brush = null;
   var renderTarget = new RenderTargetBitmap(Size, Size, 96, 96, PixelFormats.Pbgra32);
   renderTarget.Render(e);
   renderTarget.Freeze();
   brush = new ImageBrush(renderTarget);
 
   var material = new DiffuseMaterial(brush);
   _particleModel.Material = material;
  }
 
  public int XParticleCount { get; set; }
  public int YParticleCount { get; set; }
  public Model3D ParticleModel => _particleModel;
  private double _count = 0;
 
  public void Update()
  {
   // 計算粒子位置及大小
   for (int ix = 0; ix < XParticleCount; ix++)
   {
    for (int iy = 0; iy < YParticleCount; iy++)
    {
     foreach (var p in _particleList)
     {
      if(p.XIndex == ix && p.YIndex == iy)
      {
       p.Position.Z = (Math.Sin((ix + _count) * 0.3) * 100) + (Math.Sin((iy + _count) * 0.5) * 100);
       p.Size = (Math.Sin((ix + _count) * 0.3) + 1) * 8 + (Math.Sin((iy + _count) * 0.5) + 1) * 8;
      }
     }
    }
   }
   _count += 0.1;
 
   UpdateGeometry();
  }
 
  private void UpdateGeometry()
  {
   var positions = new Point3DCollection();
   var indices = new Int32Collection();
   var texcoords = new PointCollection();
 
   for (var i = 0; i < _particleList.Count; ++i)
   {
    var positionIndex = i * 4;
    var indexIndex = i * 6;
    var p = _particleList[i];
 
    var p1 = new Point3D(p.Position.X, p.Position.Y, p.Position.Z);
    var p2 = new Point3D(p.Position.X, p.Position.Y + p.Size, p.Position.Z);
    var p3 = new Point3D(p.Position.X + p.Size, p.Position.Y + p.Size, p.Position.Z);
    var p4 = new Point3D(p.Position.X + p.Size, p.Position.Y, p.Position.Z);
 
    positions.Add(p1);
    positions.Add(p2);
    positions.Add(p3);
    positions.Add(p4);
 
    var t1 = new Point(0.0, 0.0);
    var t2 = new Point(0.0, 1.0);
    var t3 = new Point(1.0, 1.0);
    var t4 = new Point(1.0, 0.0);
 
    texcoords.Add(t1);
    texcoords.Add(t2);
    texcoords.Add(t3);
    texcoords.Add(t4);
 
    indices.Add(positionIndex);
    indices.Add(positionIndex + 2);
    indices.Add(positionIndex + 1);
    indices.Add(positionIndex);
    indices.Add(positionIndex + 3);
    indices.Add(positionIndex + 2);
   }
 
   ((MeshGeometry3D)_particleModel.Geometry).Positions = positions;
   ((MeshGeometry3D)_particleModel.Geometry).TriangleIndices = indices;
   ((MeshGeometry3D)_particleModel.Geometry).TextureCoordinates = texcoords;
  }
 
  public void SpawnParticle(double size)
  {
   // 初始化粒子位置和大小
   for (int ix = 0; ix < XParticleCount; ix++)
   {
    for (int iy = 0; iy < YParticleCount; iy++)
    {
     var p = new Particle
     {
      Position = new Point3D(ix * SEPARATION - ((XParticleCount * SEPARATION) / 2), iy * SEPARATION - ((YParticleCount * SEPARATION) / 2), 0),
      Size = size,
      XIndex = ix,
      YIndex = iy,
     };
     _particleList.Add(p);
    }
   }
  }
 }

<Viewport3D Name="World">
   <Viewport3D.Camera>
    <PerspectiveCamera Position="0,50,1000" LookDirection="0,2,-1" UpDirection="0,-1,-1" FieldOfView="10000" NearPlaneDistance="10" FarPlaneDistance="8000"/>
   </Viewport3D.Camera>
   <Viewport3D.Children>
    <ModelVisual3D>
     <ModelVisual3D.Content>
      <Model3DGroup x:Name="WorldModels">
       <AmbientLight Color="#FFFFFFFF" />
      </Model3DGroup>
     </ModelVisual3D.Content>
    </ModelVisual3D>
   </Viewport3D.Children>
</Viewport3D>

private readonly ParticleSystem _ps;
private DispatcherTimer _frameTimer;
 
  public MainWindow()
  {
   InitializeComponent();
 
   _frameTimer = new DispatcherTimer();
   _frameTimer.Tick += OnFrame;
   _frameTimer.Interval = TimeSpan.FromSeconds(1.0 / 60.0);
   _frameTimer.Start();
 
   _ps = new ParticleSystem(50, 50, Colors.White, 30);
 
   WorldModels.Children.Add(_ps.ParticleModel);
 
   _ps.SpawnParticle(30);
 
   KeyDown += Window_KeyDown;
   Cursor = Cursors.None;
  }
 
  private void Window_KeyDown(object sender, KeyEventArgs e)
  {
   if (e.Key == Key.Escape)
    Close();
  }
 
  private void OnFrame(object sender, EventArgs e)
  {
   _ps.Update();
 }