所以，我試圖找到一種方法來找到我的點將擊中的第一個矩形（從矩形列表中，所有 2D），沿著特定方向（在 C# 中），但是我似乎無法正確描述術語（如果有這樣的東西，我發現最接近的東西是光線投射）。我的目標是從一個特定的“點”開始（在這種情況下，從下面的示例中可以看到星號-*），然后從那里選擇一個特定的方向（左、右、下、上）（無角度）。所以假設我們選擇 Down，那么它會命中的第一個矩形是“I'M A RECT 2”，因此應該返回這個。我已經知道矩形的所有位置和大小，所以我得到了這些信息。我該怎么做呢？ * [I'M A RECT 1][I'M A RECT 2] [I'M A RECT 3][I'M A RECT 4]
1 回答
慕碼人2483693
TA貢獻1860條經驗 獲得超9個贊
您可以檢查矩形是否可以與源自該點的射線相交，然后計算與 的距離point：
var point = new PointF(1.2f, 2.5f);
var rectangles = new RectangleF[]
{
new RectangleF(1, 1, 1, 1),
new RectangleF(3, 1, 1, 1),
new RectangleF(5, 2, 1, 1),
};
var hit = rectangles
.Select(x =>
{
if (IsBetween(point.X, x.Left, x.Left + x.Width))
return new { Rectangle = x, Distance = GetClosestDistance(point.Y, x.Top - x.Height, x.Top) as float? };
else if (IsBetween(point.X, x.Top - x.Height, x.Top))
return new { Rectangle = x, Distance = GetClosestDistance(point.Y, x.Left, x.Left + x.Width) as float? };
else return new { Rectangle = x, Distance = default(float?) };
})
.Where(x => x.Distance != null)
.OrderBy(x => x.Distance)
.FirstOrDefault()?.Rectangle;
bool IsBetween(float value, float lBound, float uBound) => lBound <= value && value <= uBound;
float GetClosestDistance(float value, float p0, float p1) => Math.Min(Math.Abs(p0 - value), Math.Abs(p1 - value));
編輯：
var hit = RayTest(point, rectangles, RayDirections.Right | RayDirections.Down) // or, try just `Down`
.Where(x => x.Success)
.OrderBy(x => x.Distance)
.FirstOrDefault()?.Target;
[Flags]
public enum RayDirections { None = 0, Left = 1 << 0, Up = 1 << 1, Right = 1 << 2, Down = 1 << 3, All = (1 << 4) - 1 }
public class RayHit<T>
{
public T Target { get; }
public float? Distance { get; }
public bool Success => Distance.HasValue;
public RayHit(T target, float? distance)
{
this.Target = target;
this.Distance = distance;
}
}
public IEnumerable<RayHit<RectangleF>> RayTest(PointF point, IEnumerable<RectangleF> rectangles, RayDirections directions = RayDirections.All)
{
if (directions == RayDirections.None)
return Enumerable.Empty<RayHit<RectangleF>>();
var ray = new
{
Horizontal = new
{
LBound = directions.HasFlag(RayDirections.Left) ? float.MinValue : point.X,
UBound = directions.HasFlag(RayDirections.Right) ? float.MaxValue : point.X,
},
Vertical = new
{
LBound = directions.HasFlag(RayDirections.Down) ? float.MinValue : point.Y,
UBound = directions.HasFlag(RayDirections.Up) ? float.MaxValue : point.Y,
},
};
return rectangles
.Select(x =>
{
float left = x.Left, right = x.Left + x.Width;
float top = x.Top, bottom = x.Top - x.Height;
if (IsBetween(point.X, left, right) && (IsBetween(top, ray.Vertical.LBound, ray.Vertical.UBound) || IsBetween(bottom, ray.Vertical.LBound, ray.Vertical.UBound)))
return new RayHit<RectangleF>(x, GetClosestDistance(point.Y, bottom, top) as float?);
else if (IsBetween(point.X, bottom, top) && (IsBetween(left, ray.Horizontal.LBound, ray.Horizontal.UBound) || IsBetween(right, ray.Horizontal.LBound, ray.Horizontal.UBound)))
return new RayHit<RectangleF>(x, GetClosestDistance(point.Y, left, right) as float?);
else return new RayHit<RectangleF>(x, default);
});
bool IsBetween(float value, float lBound, float uBound) => lBound <= value && value <= uBound;
float GetClosestDistance(float value, float p0, float p1) => Math.Min(Math.Abs(p0 - value), Math.Abs(p1 - value));
}
注意：在這兩個版本中，當點在矩形內時都會出現錯誤。計算的距離將是到最近邊緣的距離，而不是 0 或負值。
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