SkiaSharp 之 WPF 自绘粒子花园（案例版）

吴旭华 · 2022-9-16 17:14:53

此案例包含了简单的碰撞检测，圆形碰撞检测方法，也可以说是五环弹球的升级版，具体可以根据例子参考。

粒子花园

这名字是案例的名字，效果更加具有科技感，很是不错，搞搞做成背景特效也是不错的选择。
Wpf 和 SkiaSharp

新建一个 WPF 项目，然后，Nuget 包即可
要添加 Nuget 包

Install-Package SkiaSharp.Views.WPF -Version 2.88.0

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其中核心逻辑是这部分，会以我设置的 60FPS 来刷新当前的画板。

skContainer.PaintSurface += SkContainer_PaintSurface;
_ = Task.Run(() =>
{
while (true)
{
try
{
Dispatcher.Invoke(() =>
{
skContainer.InvalidateVisual();
});
_ = SpinWait.SpinUntil(() => false, 1000 / 60);//每秒60帧
}
catch
{
break;
}
}
});

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弹球实体代码 (Ball.cs)

public class Ball
{
public double X { get; set; }
public double Y { get; set; }
public double VX { get; set; }
public double VY { get; set; }
public int Radius { get; set; }
public int Move { get; set; }
public SKColor sKColor { get; set; } = SKColors.Blue;
/// <summary>
/// 检查球的碰撞
/// </summary>
public static void CheckBallHit(Ball b1, Ball b2)
{
var dx = b2.X - b1.X;
var dy = b2.Y - b1.Y;
var dist = Math.Sqrt(Math.Pow(dx,2) + Math.Pow(dy, 2));
if (dist < b1.Radius + b2.Radius)
{
var angle = Math.Atan2(dy, dx);
var sin = Math.Sin(angle);
var cos = Math.Cos(angle);
// 以b1为参照物，设定b1的中心点为旋转基点
double x1 = 0;
double y1 = 0;
var x2 = dx * cos + dy * sin;
var y2 = dy * cos - dx * sin;
// 旋转b1和b2的速度
var vx1 = b1.VX * cos + b1.VY * sin;
var vy1 = b1.VY * cos - b1.VX * sin;
var vx2 = b2.VX * cos + b2.VY * sin;
var vy2 = b2.VY * cos - b2.VX * sin;
// 求出b1和b2碰撞之后的速度
var vx1Final = ((b1.Move - b2.Move) * vx1 + 2 * b2.Move * vx2) / (b1.Move + b2.Move);
var vx2Final = ((b2.Move - b1.Move) * vx2 + 2 * b1.Move * vx1) / (b1.Move + b2.Move);
// 处理两个小球碰撞之后，将它们进行归位
var lep = (b1.Radius + b2.Radius) - Math.Abs(x2 - x1);
x1 = x1 + (vx1Final < 0 ? -lep / 2 : lep / 2);
x2 = x2 + (vx2Final < 0 ? -lep / 2 : lep / 2);
b2.X = b1.X + (x2 * cos - y2 * sin);
b2.Y = b1.Y + (y2 * cos + x2 * sin);
b1.X = b1.X + (x1 * cos - y1 * sin);
b1.Y = b1.Y + (y1 * cos + x1 * sin);
b1.VX = vx1Final * cos - vy1 * sin;
b1.VY = vy1 * cos + vx1Final * sin;
b2.VX = vx2Final * cos - vy2 * sin;
b2.VY = vy2 * cos + vx2Final * sin;
}
}
}

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粒子花园核心类 (ParticleGarden.cs)

/// <summary>
/// 粒子花园
/// </summary>
public class ParticleGarden
{
public SKPoint centerPoint;
public double Spring = 0.0001;
public int ParticelCount = 100;
public List<Ball> Particles = new List<Ball>();
public SKCanvas canvas;
/// <summary>
/// 渲染
/// </summary>
public void Render(SKCanvas canvas, SKTypeface Font, int Width, int Height)
{
this.canvas = canvas;
canvas.Clear(SKColors.Black);
centerPoint = new SKPoint(Width / 2, Height / 2);
if (Particles.Any() == false)
{
for (int i = 0; i < ParticelCount; i++)
{
Random random = new Random((int)DateTime.Now.Ticks);
var Length = random.Next(3, 10);
Particles.Add(new Ball()
{
X = random.Next(0, Width),
Y = random.Next(0, Height),
sKColor = SKColors.White,
VX = random.NextInt64(-2, 2),
VY = random.NextInt64(-2, 2),
Radius = Length,
Move = Length
});
}
}
//画线
for (int i = 0; i < Particles.Count; i++)
{
Move(Particles[i], i, Width, Height);
}
//画球
foreach (var item in Particles)
{
DrawCircle(canvas, item);
}
using var paint = new SKPaint
{
Color = SKColors.Blue,
IsAntialias = true,
Typeface = Font,
TextSize = 24
};
string by = $"by 蓝创精英团队";
canvas.DrawText(by, 600, 400, paint);
}
public void Move(Ball p, int i, int width, int height)
{
p.X += p.VX;
p.Y += p.VY;
for (var j = i + 1; j < Particles.Count; j++)
{
var target = Particles[j];
CheckSpring(p, target, width, height);
Ball.CheckBallHit(p, target);
}
if (p.X - p.Radius > width)
{
p.X = -p.Radius;
}
else if (p.X + p.Radius < 0)
{
p.X = width + p.Radius;
}
if (p.Y - p.Radius > height)
{
p.Y = -p.Radius;
}
else if (p.Y + p.Radius < 0)
{
p.Y = height + p.Radius;
}
}
public void CheckSpring(Ball current, Ball target, int width, int height)
{
var dx = target.X - current.X;
var dy = target.Y - current.Y;
var dist = Math.Sqrt(Math.Pow(dx, 2) + Math.Pow(dy, 2));
var minDist = width > height ? width / 10 : height / 5;
if (dist < minDist)
{
DrawLine(current, target, dist, minDist);
var ax = dx * Spring;
var ay = dy * Spring;
current.VX += ax / current.Move;
current.VY += ay / current.Move;
target.VX -= ax / target.Move;
target.VY -= ay / target.Move;
}
}
public void DrawLine(Ball current, Ball target, double dist, int minDist)
{
var StrokeWidth = (float)(2 * Math.Max(0, (1 - dist / minDist)));
var Alpha = Math.Max(0, (1 - dist / minDist)) * byte.MaxValue;
var Color = current.sKColor.WithAlpha((byte)Alpha);
//划线
using var LinePaint = new SKPaint
{
Color = Color,
Style = SKPaintStyle.Fill,
StrokeWidth = StrokeWidth,
IsStroke = true,
StrokeCap = SKStrokeCap.Round,
IsAntialias = true
};
var path = new SKPath();
path.MoveTo((float)current.X, (float)current.Y);
path.LineTo((float)target.X, (float)target.Y);
path.Close();
canvas.DrawPath(path, LinePaint);
}
/// <summary>
/// 画一个圆
/// </summary>
public void DrawCircle(SKCanvas canvas, Ball ball)
{
using var paint = new SKPaint
{
Color = ball.sKColor,
Style = SKPaintStyle.Fill,
IsAntialias = true,
StrokeWidth = 2
};
canvas.DrawCircle((float)ball.X, (float)ball.Y, ball.Radius, paint);
}
}

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效果如下:

效果放大看，还是很心旷神怡的。
总结

这个特效的案例重点是碰撞检测，同时又产生了奇妙的特效效果，很是不错。
代码地址

https://github.com/kesshei/WPFSkiaParticleGardenDemo.git
https://gitee.com/kesshei/WPFSkiaParticleGardenDemo.git
阅

一键三连呦！，感谢大佬的支持，您的支持就是我的动力!
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