Question

我收到了一个把病媒推向前进的游戏台。病媒的数值范围界定了介于1、1至+1、+1的试金体内的循环。

我想知道,8个可能的方向中,病媒接近什么。我对病媒(0、0)的病例表示担忧,单独处理。 <>?

Note: This is for a game, so this function will be ran very frequently. Anything to speed up the function would help, for example I know I could use the dot product and trig to work out the angle between my vector and each direction vector, however I wonder if something better could be done given I don t need the exact angle.

Answer 1

Imagine a square inside the -1..1 square, where the stick position (X) is on one of the sides:

+-----------------+  +-----------------+
|                 |  |                 |
|                 |  |                 |
|          X      |  |    +-----X-+    |
|                 |  |    |       |    |
|        O        |  |    |   O   |    |
|                 |  |    |       |    |
|                 |  |    +-------+    |
|                 |  |                 |
|                 |  |                 |
+-----------------+  +-----------------+

你必须找到坐标的哪一方,并检查它是否靠近一方的中心,还是一角。如果内地面积太小,你可以认为该带是集中的。

Something like:

Public enum Direction {
  None,
  LeftUp, Up, RightUp, Right, RightDown, Down, LeftDown, Left
}

public Direction GetDirection(double x, double y) {
  double absX = Math.Abs(x);
  double absY = Math.Abs(y);
  if (absX < 0.1 && absY < 0.1) {
    // close to center
    return Direction.None;
  }
  if (absX > absY) {
    // vertical side
    double half = absX * 0.4142;
    if (x > 0) {
      // left side
      if (y > half) return Direction.LeftDown;
      if (y < -half) return Diretion.LeftUp;
      return Direction.Left;
    } else {
      // right side
      if (y > half) return Direction.RightDown;
      if (y < -half) return Direction.RightUp;
      return Direction.Right;
    }
  } else {
    // horisontal side
    double half = absY * 0.4142;
    if (y > 0) {
      // bottom
      if (x > half) return Direction.RightDown;
      if (x < -half) return Direction.LeftDown;
      return Direction.Down;
    } else {
      // top
      if (x > half) return Direction.RightUp;
      if (x < -half) return Direction.LeftUp;
      return Direction.Up;
    }
  }
}

无三角,只是简单比较,因此应当迅速。

(尽管我使用了三角,计算出0.4142点,即:tan(22.5),或角线为45/2的一侧的位置。)

Answer 2

sina = tana

页: 1

Y = 罪状

X = coa

因此,对Y/X适用反向的附带功能,而你则倾向于。

EDIT: In a full circle, there are two angles with the same tangent value (a and a + pi). Use the sign of X and Y to determine which one is the valid one.

Answer 3

您可使用一个tan-1的预定近似值表。根据您的病媒投入的规模计算出一个角,或许你胜出的必然需要一个非常大的分辨率(事实上,如果你只想8个不同的方向,那么,你表格中的8个条目就足够了)。

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