此案例主要是針對光線投影法碰撞檢測功能的範例，順便做成了一個小遊戲，很簡單，但是，效果卻很不錯。

投籃小遊戲

規則，點選投籃目標點，就會有一個球沿著相關拋物線，然後，判斷是否進入籃子裡，其實就是一個矩形，直接是按照碰撞檢測來的，碰到就算進去了，對其增加了一個分數統計等功能。

Wpf 和 SkiaSharp

新建一個 WPF 專案，然後，Nuget 包即可
要新增 Nuget 包

Install-Package SkiaSharp.Views.WPF -Version 2.88.0

其中核心邏輯是這部分，會以我設定的 60FPS 來重新整理當前的畫板。

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

彈球實體程式碼 (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; }
}

粒子花園核心類 (ParticleGarden.cs)

/// <summary>
/// 光線投影法碰撞檢測
/// 投籃小遊戲
/// </summary>
public class RayProjection
{
    public SKPoint centerPoint;
    public double G = 0.3;
    public double F = 0.98;
    public double Easing = 0.03;
    public bool IsMoving = false;
    public SKPoint CurrentMousePoint = SKPoint.Empty;
    public SKPoint lastPoint = SKPoint.Empty;
    public Rect Box;
    public Ball Ball;
    public SKCanvas canvas;
    public int ALLCount = 10;
    public List<bool> bools = new List<bool>();
    public bool IsOver = false;
    /// <summary>
    /// 渲染
    /// </summary>
    public void Render(SKCanvas canvas, SKTypeface Font, int Width, int Height)
    {
        canvas.Clear(SKColors.White);
        this.canvas = canvas;
        centerPoint = new SKPoint(Width / 2, Height / 2);
        //球
        if (Ball == null)
        {
            Ball = new Ball()
            {
                X = 50,
                Y = Height - 50,
                Radius = 30
            };
        }
        //箱子
        var boxX = Width - 170;
        var boxY = Height - 80;
        if (Box.X == 0)
        {
            Box = new Rect(boxX, boxY, 120, 70);
        }
        else
        {
            if (Box.X != boxX && Box.Y != boxY)
            {
                Box.X = boxX;
                Box.Y = boxY;
            }
        }

        if (bools.Count >= ALLCount)
        {
            IsOver = true;
        }

        if (!IsOver)
        {
            if (IsMoving)
            {
                BallMove(Width, Height);
            }
            else
            {
                DrawLine();
            }

            //彈球
            DrawCircle(canvas, Ball);
            //矩形
            DrawRect(canvas, Box);

            //計分
            using var paint1 = new SKPaint
            {
                Color = SKColors.Blue,
                IsAntialias = true,
                Typeface = Font,
                TextSize = 24
            };
            string count = $"總次數:{ALLCount} 剩餘次數:{ALLCount - bools.Count} 投中次數:{bools.Count(t => t)}";
            canvas.DrawText(count, 100, 20, paint1);
        }
        else
        {
            SKColor sKColor = SKColors.Blue;
            //計分
            var SuccessCount = bools.Count(t => t);
            string count = "";
            switch (SuccessCount)
            {
                case 0:
                    {
                        count = $"太糗了吧，一個都沒投中！";
                        sKColor = SKColors.Black;
                    }
                    break;
                case 1:
                case 2:
                case 3:
                case 4:
                case 5:
                    {
                        count = $"你才投中:{SuccessCount}次，繼續努力！";
                        sKColor = SKColors.Blue;
                    }
                    break;
                case 6:
                case 7:
                case 8:
                case 9:
                    {
                        count = $"恭喜 投中:{SuccessCount}次!!!";
                        sKColor = SKColors.YellowGreen;
                    }
                    break;
                case 10: { count = $"全部投中，你太厲害了!";
                        sKColor = SKColors.Red;
                    } break;
            }
            using var paint1 = new SKPaint
            {
                Color = sKColor,
                IsAntialias = true,
                Typeface = Font,
                TextSize = 48
            };
            var fontCenter = paint1.MeasureText(count);
            canvas.DrawText(count, centerPoint.X - fontCenter / 2, centerPoint.Y, paint1);
        }
        using var paint = new SKPaint
        {
            Color = SKColors.Blue,
            IsAntialias = true,
            Typeface = Font,
            TextSize = 24
        };
        string by = $"by 藍創精英團隊";
        canvas.DrawText(by, 600, 20, paint);
    }
    /// <summary>
    /// 畫一個圓
    /// </summary>
    public void DrawCircle(SKCanvas canvas, Ball ball)
    {
        using var paint = new SKPaint
        {
            Color = SKColors.Blue,
            Style = SKPaintStyle.Fill,
            IsAntialias = true,
            StrokeWidth = 2
        };
        canvas.DrawCircle((float)ball.X, (float)ball.Y, ball.Radius, paint);
    }
    /// <summary>
    /// 畫一個矩形
    /// </summary>
    public void DrawRect(SKCanvas canvas, Rect box)
    {
        using var paint = new SKPaint
        {
            Color = SKColors.Green,
            Style = SKPaintStyle.Fill,
            IsAntialias = true,
            StrokeWidth = 2
        };
        canvas.DrawRect((float)box.X, (float)box.Y, (float)box.Width, (float)box.Height, paint);
    }
    /// <summary>
    /// 劃線
    /// </summary>
    public void DrawLine()
    {
        //劃線
        using var LinePaint = new SKPaint
        {
            Color = SKColors.Red,
            Style = SKPaintStyle.Fill,
            StrokeWidth = 2,
            IsStroke = true,
            StrokeCap = SKStrokeCap.Round,
            IsAntialias = true
        };
        var path = new SKPath();
        path.MoveTo((float)CurrentMousePoint.X, (float)CurrentMousePoint.Y);
        path.LineTo((float)Ball.X, (float)Ball.Y);
        path.Close();
        canvas.DrawPath(path, LinePaint);
    }
    public void BallMove(int Width, int Height)
    {
        Ball.VX *= F;
        Ball.VY *= F;
        Ball.VY += G;

        Ball.X += Ball.VX;
        Ball.Y += Ball.VY;

        var hit = CheckHit();
        // 邊界處理和碰撞檢測
        if (hit || Ball.X - Ball.Radius > Width || Ball.X + Ball.Radius < 0 || Ball.Y - Ball.Radius > Height || Ball.Y + Ball.Radius < 0)
        {
            bools.Add(hit);
            IsMoving = false;
            Ball.X = 50;
            Ball.Y = Height - 50;
        }

        lastPoint.X = (float)Ball.X;
        lastPoint.Y = (float)Ball.Y;
    }
    public bool CheckHit()
    {
        var k1 = (Ball.Y - lastPoint.Y) / (Ball.X - lastPoint.X);
        var b1 = lastPoint.Y - k1 * lastPoint.X;
        var k2 = 0;
        var b2 = Ball.Y;
        var cx = (b2 - b1) / (k1 - k2);
        var cy = k1 * cx + b1;
        if (cx - Ball.Radius / 2 > Box.X && cx + Ball.Radius / 2 < Box.X + Box.Width && Ball.Y - Ball.Radius > Box.Y)
        {
            return true;
        }
        return false;
    }
    public void MouseMove(SKPoint sKPoint)
    {
        CurrentMousePoint = sKPoint;
    }
    public void MouseDown(SKPoint sKPoint)
    {
        CurrentMousePoint = sKPoint;
    }
    public void MouseUp(SKPoint sKPoint)
    {
        if (bools.Count < ALLCount)
        {
            IsMoving = true;
            Ball.VX = (sKPoint.X - Ball.X) * Easing;
            Ball.VY = (sKPoint.Y - Ball.Y) * Easing;
            lastPoint.X = (float)Ball.X;
            lastPoint.Y = (float)Ball.Y;
        }
    }
}

效果如下:

還不錯，得了7分，當然，我也可以得10分的，不過，還好了。

總結

這個特效的案例重點是光線投影法碰撞檢測，同時又對其增加了遊戲的屬性，雖然東西都很簡單，但是作為一個雛形來講也是不錯的。

SkiaSharp 基礎系列算是告一段落了，基礎知識相關暫時都已經有了一個深度的瞭解，對於它的基礎應用已經有一個不錯的認識了，那麼，基於它的應用應該也會多起來，我這邊主要參考Avalonia的內部SkiaSharp使用原理，當然，用法肯定不侷限的。

程式碼地址

https://github.com/kesshei/WPFSkiaRayProjectionDemo.git

https://gitee.com/kesshei/WPFSkiaRayProjectionDemo.git

閱

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