Yay tôi tìm thấy một bài nghiên cứu!
Xét về chi phí tính toán, Shadow Mapping có vẻ là người chiến thắng khá rõ ràng.
Thuật toán được sử dụng có thể được tìm thấy ở đây và triển khai C # có thể được tìm thấy ở đây , bit có liên quan bên dưới.
#region FOV algorithm
// Octant data
//
// \ 1 | 2 /
// 8 \ | / 3
// -----+-----
// 7 / | \ 4
// / 6 | 5 \
//
// 1 = NNW, 2 =NNE, 3=ENE, 4=ESE, 5=SSE, 6=SSW, 7=WSW, 8 = WNW
/// <summary>
/// Start here: go through all the octants which surround the player to
/// determine which open cells are visible
/// </summary>
public void GetVisibleCells()
{
VisiblePoints = new List<Point>();
foreach (int o in VisibleOctants)
ScanOctant(1, o, 1.0, 0.0);
}
/// <summary>
/// Examine the provided octant and calculate the visible cells within it.
/// </summary>
/// <param name="pDepth">Depth of the scan</param>
/// <param name="pOctant">Octant being examined</param>
/// <param name="pStartSlope">Start slope of the octant</param>
/// <param name="pEndSlope">End slope of the octance</param>
protected void ScanOctant(int pDepth, int pOctant, double pStartSlope, double pEndSlope)
{
int visrange2 = VisualRange * VisualRange;
int x = 0;
int y = 0;
switch (pOctant)
{
case 1: //nnw
y = player.Y - pDepth;
if (y < 0) return;
x = player.X - Convert.ToInt32((pStartSlope * Convert.ToDouble(pDepth)));
if (x < 0) x = 0;
while (GetSlope(x, y, player.X, player.Y, false) >= pEndSlope)
{
if (GetVisDistance(x, y, player.X, player.Y) <= visrange2)
{
if (map[x, y] == 1) //current cell blocked
{
if (x - 1 >= 0 && map[x - 1, y] == 0) //prior cell within range AND open...
//...incremenet the depth, adjust the endslope and recurse
ScanOctant(pDepth + 1, pOctant, pStartSlope, GetSlope(x - 0.5, y + 0.5, player.X, player.Y, false));
}
else
{
if (x - 1 >= 0 && map[x - 1, y] == 1) //prior cell within range AND open...
//..adjust the startslope
pStartSlope = GetSlope(x - 0.5, y - 0.5, player.X, player.Y, false);
VisiblePoints.Add(new Point(x, y));
}
}
x++;
}
x--;
break;
case 2: //nne
y = player.Y - pDepth;
if (y < 0) return;
x = player.X + Convert.ToInt32((pStartSlope * Convert.ToDouble(pDepth)));
if (x >= map.GetLength(0)) x = map.GetLength(0) - 1;
while (GetSlope(x, y, player.X, player.Y, false) <= pEndSlope)
{
if (GetVisDistance(x, y, player.X, player.Y) <= visrange2)
{
if (map[x, y] == 1)
{
if (x + 1 < map.GetLength(0) && map[x + 1, y] == 0)
ScanOctant(pDepth + 1, pOctant, pStartSlope, GetSlope(x + 0.5, y + 0.5, player.X, player.Y, false));
}
else
{
if (x + 1 < map.GetLength(0) && map[x + 1, y] == 1)
pStartSlope = -GetSlope(x + 0.5, y - 0.5, player.X, player.Y, false);
VisiblePoints.Add(new Point(x, y));
}
}
x--;
}
x++;
break;
case 3:
x = player.X + pDepth;
if (x >= map.GetLength(0)) return;
y = player.Y - Convert.ToInt32((pStartSlope * Convert.ToDouble(pDepth)));
if (y < 0) y = 0;
while (GetSlope(x, y, player.X, player.Y, true) <= pEndSlope)
{
if (GetVisDistance(x, y, player.X, player.Y) <= visrange2)
{
if (map[x, y] == 1)
{
if (y - 1 >= 0 && map[x, y - 1] == 0)
ScanOctant(pDepth + 1, pOctant, pStartSlope, GetSlope(x - 0.5, y - 0.5, player.X, player.Y, true));
}
else
{
if (y - 1 >= 0 && map[x, y - 1] == 1)
pStartSlope = -GetSlope(x + 0.5, y - 0.5, player.X, player.Y, true);
VisiblePoints.Add(new Point(x, y));
}
}
y++;
}
y--;
break;
case 4:
x = player.X + pDepth;
if (x >= map.GetLength(0)) return;
y = player.Y + Convert.ToInt32((pStartSlope * Convert.ToDouble(pDepth)));
if (y >= map.GetLength(1)) y = map.GetLength(1) - 1;
while (GetSlope(x, y, player.X, player.Y, true) >= pEndSlope)
{
if (GetVisDistance(x, y, player.X, player.Y) <= visrange2)
{
if (map[x, y] == 1)
{
if (y + 1 < map.GetLength(1)&& map[x, y + 1] == 0)
ScanOctant(pDepth + 1, pOctant, pStartSlope, GetSlope(x - 0.5, y + 0.5, player.X, player.Y, true));
}
else
{
if (y + 1 < map.GetLength(1) && map[x, y + 1] == 1)
pStartSlope = GetSlope(x + 0.5, y + 0.5, player.X, player.Y, true);
VisiblePoints.Add(new Point(x, y));
}
}
y--;
}
y++;
break;
case 5:
y = player.Y + pDepth;
if (y >= map.GetLength(1)) return;
x = player.X + Convert.ToInt32((pStartSlope * Convert.ToDouble(pDepth)));
if (x >= map.GetLength(0)) x = map.GetLength(0) - 1;
while (GetSlope(x, y, player.X, player.Y, false) >= pEndSlope)
{
if (GetVisDistance(x, y, player.X, player.Y) <= visrange2)
{
if (map[x, y] == 1)
{
if (x + 1 < map.GetLength(1) && map[x+1, y] == 0)
ScanOctant(pDepth + 1, pOctant, pStartSlope, GetSlope(x + 0.5, y - 0.5, player.X, player.Y, false));
}
else
{
if (x + 1 < map.GetLength(1)
&& map[x + 1, y] == 1)
pStartSlope = GetSlope(x + 0.5, y + 0.5, player.X, player.Y, false);
VisiblePoints.Add(new Point(x, y));
}
}
x--;
}
x++;
break;
case 6:
y = player.Y + pDepth;
if (y >= map.GetLength(1)) return;
x = player.X - Convert.ToInt32((pStartSlope * Convert.ToDouble(pDepth)));
if (x < 0) x = 0;
while (GetSlope(x, y, player.X, player.Y, false) <= pEndSlope)
{
if (GetVisDistance(x, y, player.X, player.Y) <= visrange2)
{
if (map[x, y] == 1)
{
if (x - 1 >= 0 && map[x - 1, y] == 0)
ScanOctant(pDepth + 1, pOctant, pStartSlope, GetSlope(x - 0.5, y - 0.5, player.X, player.Y, false));
}
else
{
if (x - 1 >= 0
&& map[x - 1, y] == 1)
pStartSlope = -GetSlope(x - 0.5, y + 0.5, player.X, player.Y, false);
VisiblePoints.Add(new Point(x, y));
}
}
x++;
}
x--;
break;
case 7:
x = player.X - pDepth;
if (x < 0) return;
y = player.Y + Convert.ToInt32((pStartSlope * Convert.ToDouble(pDepth)));
if (y >= map.GetLength(1)) y = map.GetLength(1) - 1;
while (GetSlope(x, y, player.X, player.Y, true) <= pEndSlope)
{
if (GetVisDistance(x, y, player.X, player.Y) <= visrange2)
{
if (map[x, y] == 1)
{
if (y + 1 < map.GetLength(1) && map[x, y+1] == 0)
ScanOctant(pDepth + 1, pOctant, pStartSlope, GetSlope(x + 0.5, y + 0.5, player.X, player.Y, true));
}
else
{
if (y + 1 < map.GetLength(1) && map[x, y + 1] == 1)
pStartSlope = -GetSlope(x - 0.5, y + 0.5, player.X, player.Y, true);
VisiblePoints.Add(new Point(x, y));
}
}
y--;
}
y++;
break;
case 8: //wnw
x = player.X - pDepth;
if (x < 0) return;
y = player.Y - Convert.ToInt32((pStartSlope * Convert.ToDouble(pDepth)));
if (y < 0) y = 0;
while (GetSlope(x, y, player.X, player.Y, true) >= pEndSlope)
{
if (GetVisDistance(x, y, player.X, player.Y) <= visrange2)
{
if (map[x, y] == 1)
{
if (y - 1 >=0 && map[x, y - 1] == 0)
ScanOctant(pDepth + 1, pOctant, pStartSlope, GetSlope(x + 0.5, y - 0.5, player.X, player.Y, true));
}
else
{
if (y - 1 >= 0 && map[x, y - 1] == 1)
pStartSlope = GetSlope(x - 0.5, y - 0.5, player.X, player.Y, true);
VisiblePoints.Add(new Point(x, y));
}
}
y++;
}
y--;
break;
}
if (x < 0)
x = 0;
else if (x >= map.GetLength(0))
x = map.GetLength(0) - 1;
if (y < 0)
y = 0;
else if (y >= map.GetLength(1))
y = map.GetLength(1) - 1;
if (pDepth < VisualRange & map[x, y] == 0)
ScanOctant(pDepth + 1, pOctant, pStartSlope, pEndSlope);
}
/// <summary>
/// Get the gradient of the slope formed by the two points
/// </summary>
/// <param name="pX1"></param>
/// <param name="pY1"></param>
/// <param name="pX2"></param>
/// <param name="pY2"></param>
/// <param name="pInvert">Invert slope</param>
/// <returns></returns>
private double GetSlope(double pX1, double pY1, double pX2, double pY2, bool pInvert)
{
if (pInvert)
return (pY1 - pY2) / (pX1 - pX2);
else
return (pX1 - pX2) / (pY1 - pY2);
}
/// <summary>
/// Calculate the distance between the two points
/// </summary>
/// <param name="pX1"></param>
/// <param name="pY1"></param>
/// <param name="pX2"></param>
/// <param name="pY2"></param>
/// <returns>Distance</returns>
private int GetVisDistance(int pX1, int pY1, int pX2, int pY2)
{
return ((pX1 - pX2) * (pX1 - pX2)) + ((pY1 - pY2) * (pY1 - pY2));
}
#endregion
