【发布时间】：2013-04-13 00:56:21
【问题描述】：
我需要在 WPF 中绘制大量的 2D 元素，例如线条和多边形。他们的立场也需要不断更新。
我在这里查看了许多答案，这些答案大多建议使用 DrawingVisual 或覆盖 OnRender 函数。为了测试这些方法，我实现了一个简单的粒子系统渲染 10000 个椭圆，我发现使用这两种方法的绘图性能仍然非常糟糕。在我的 PC 上，每秒的帧数不能超过 5-10 帧。当您考虑到我使用其他技术轻松绘制 1/2 百万个粒子时，这是完全不能接受的。
所以我的问题是，我是在违反 WPF 的技术限制还是我错过了什么？还有什么我可以使用的吗？欢迎任何建议。
这是我试过的代码
MainWindow.xaml 的内容：
<Window x:Class="WpfApplication1.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="500" Width="500" Loaded="Window_Loaded">
<Grid Name="xamlGrid">
</Grid>
</Window>
MainWindow.xaml.cs 的内容：
using System.Windows.Threading;
namespace WpfApplication1
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
}
EllipseBounce[] _particles;
DispatcherTimer _timer = new DispatcherTimer();
private void Window_Loaded(object sender, RoutedEventArgs e)
{
//particles with Ellipse Geometry
_particles = new EllipseBounce[10000];
//define area particles can bounce around in
Rect stage = new Rect(0, 0, 500, 500);
//seed particles with random velocity and position
Random rand = new Random();
//populate
for (int i = 0; i < _particles.Length; i++)
{
Point pos = new Point((float)(rand.NextDouble() * stage.Width + stage.X), (float)(rand.NextDouble() * stage.Height + stage.Y));
Point vel = new Point((float)(rand.NextDouble() * 5 - 2.5), (float)(rand.NextDouble() * 5 - 2.5));
_particles[i] = new EllipseBounce(stage, pos, vel, 2);
}
//add to particle system - this will draw particles via onrender method
ParticleSystem ps = new ParticleSystem(_particles);
//at this element to the grid (assumes we have a Grid in xaml named 'xmalGrid'
xamlGrid.Children.Add(ps);
//set up and update function for the particle position
_timer.Tick += _timer_Tick;
_timer.Interval = new TimeSpan(0, 0, 0, 0, 1000 / 60); //update at 60 fps
_timer.Start();
}
void _timer_Tick(object sender, EventArgs e)
{
for (int i = 0; i < _particles.Length; i++)
{
_particles[i].Update();
}
}
}
/// <summary>
/// Framework elements that draws particles
/// </summary>
public class ParticleSystem : FrameworkElement
{
private DrawingGroup _drawingGroup;
public ParticleSystem(EllipseBounce[] particles)
{
_drawingGroup = new DrawingGroup();
for (int i = 0; i < particles.Length; i++)
{
EllipseGeometry eg = particles[i].EllipseGeometry;
Brush col = Brushes.Black;
col.Freeze();
GeometryDrawing gd = new GeometryDrawing(col, null, eg);
_drawingGroup.Children.Add(gd);
}
}
protected override void OnRender(DrawingContext drawingContext)
{
base.OnRender(drawingContext);
drawingContext.DrawDrawing(_drawingGroup);
}
}
/// <summary>
/// simple class that implements 2d particle movements that bounce from walls
/// </summary>
public class SimpleBounce2D
{
protected Point _position;
protected Point _velocity;
protected Rect _stage;
public SimpleBounce2D(Rect stage, Point pos,Point vel)
{
_stage = stage;
_position = pos;
_velocity = vel;
}
public double X
{
get
{
return _position.X;
}
}
public double Y
{
get
{
return _position.Y;
}
}
public virtual void Update()
{
UpdatePosition();
BoundaryCheck();
}
private void UpdatePosition()
{
_position.X += _velocity.X;
_position.Y += _velocity.Y;
}
private void BoundaryCheck()
{
if (_position.X > _stage.Width + _stage.X)
{
_velocity.X = -_velocity.X;
_position.X = _stage.Width + _stage.X;
}
if (_position.X < _stage.X)
{
_velocity.X = -_velocity.X;
_position.X = _stage.X;
}
if (_position.Y > _stage.Height + _stage.Y)
{
_velocity.Y = -_velocity.Y;
_position.Y = _stage.Height + _stage.Y;
}
if (_position.Y < _stage.Y)
{
_velocity.Y = -_velocity.Y;
_position.Y = _stage.Y;
}
}
}
/// <summary>
/// extend simplebounce2d to add ellipse geometry and update position in the WPF construct
/// </summary>
public class EllipseBounce : SimpleBounce2D
{
protected EllipseGeometry _ellipse;
public EllipseBounce(Rect stage,Point pos, Point vel, float radius)
: base(stage, pos, vel)
{
_ellipse = new EllipseGeometry(pos, radius, radius);
}
public EllipseGeometry EllipseGeometry
{
get
{
return _ellipse;
}
}
public override void Update()
{
base.Update();
_ellipse.Center = _position;
}
}
}
【问题讨论】：
-
我只是在做一些测试，覆盖
OnRender()并随机输入10000 个drawingContext.DrawLine()。我发现仅Freezing Freezables（例如Pen和Brush）在性能上就产生了巨大差异。 -
好的，谢谢你试试看。除了 pen（在我的实现中为 null）和 Brush 之外还有什么应该冻结的吗？
-
不幸的是，当我冻结 Brush 时，性能没有明显变化。我的测试粒子渲染器仍然只能以每秒 5 帧左右的速度运行，这实在是太慢了。以这种速度，手动将粒子绘制到 CPU 上的位图可能会更快——我只是不明白 WPF 在 DirectX 上构建时怎么会这么慢
-
贴一些示例代码...你也看过this？
-
WPF 是一个保留模式系统，在大多数情况下，重写 OnRender 是不可行的。组合你的场景并让它绘制。您可以检查一下以绘制一百万个多边形：blogs.msdn.com/b/kaelr/archive/2010/08/11/… 它正在使用“VirtualCanvas”
标签： c# wpf performance drawing drawingvisual