//The original code is public domain, and is available at:
//http://www.adammil.net/blog/v125_Roguelike_Vision_Algorithms.html#shadowcast
//The original code is modified by ChizaruuGCO to work with Unity Tilemaps and RLSKTD.
/// <summary> Field of View is computed using a shadow cast algorithm. </summary>
/// <param name="lPos"> The local position of the character. </param>
/// <param name="rangeLimit"> The range limit for the field of view. </param>
/// <param name="obstacleMap"> The obstacle map. </param>
/// <param name="fogMap"> The fog map. </param>
/// <param name="isPlayer"> Is the character the player? </param>
/// <param name="fov"> The field of view. </param>
/// <param name="isSymmetrical"> Is the field of view symmetrical? </param>
/// <returns> The field of view. </returns>
static public void FovCompute(Vector3Int lPos, int rangeLimit, Tilemap obstacleMap, Tilemap fogMap, bool isPlayer, FOV fov, bool isSymmetrical)
{
TileCompute(lPos, fogMap, isPlayer, fov);
for (uint octant = 0; octant <= 7; octant++)
{
Compute(octant, lPos, rangeLimit, 1, new Slope(1, 1), new Slope(0, 1), obstacleMap, fogMap, isPlayer, fov, isSymmetrical);
}
}
/// <summary> Compute the field of view for a given octant. </summary>
/// <param name="octant"> The octant. </param>
/// <param name="lPos"> The local position of the character. </param>
/// <param name="rangeLimit"> The range limit for the field of view. </param>
/// <param name="top"> The top of the slope. </param>
/// <param name="bottom"> The bottom of the slope. </param>
/// <param name="obstacleMap"> The obstacle map. </param>
/// <param name="fogMap"> The fog map. </param>
/// <param name="isPlayer"> Is the character the player? </param>
/// <param name="fov"> The field of view. </param>
/// <param name="isSymmetrical"> Is the field of view symmetrical? </param>
/// <returns> The field of view of a given octant. </returns>
static void Compute(uint octant, Vector3Int lPos, int rangeLimit, int x, Slope top, Slope bottom, Tilemap obstacleMap, Tilemap fogMap, bool isPlayer, FOV fov, bool isSymmetrical)
{
for (; (uint)x <= (uint)rangeLimit; x++) // rangeLimit < 0 || x <= rangeLimit
{
// compute the Y coordinates where the top vector leaves the column (on the right) and where the bottom vector
// enters the column (on the left). this equals (x+0.5)*top+0.5 and (x-0.5)*bottom+0.5 respectively, which can
// be computed like (x+0.5)*top+0.5 = (2(x+0.5)*top+1)/2 = ((2x+1)*top+1)/2 to avoid floating point math
int topY = top.X == 1 ? x : ((x * 2 + 1) * top.Y + top.X - 1) / (top.X * 2); // the rounding is a bit tricky, though
int bottomY = bottom.Y == 0 ? 0 : ((x * 2 - 1) * bottom.Y + bottom.X) / (bottom.X * 2);
int wasOpaque = -1; // 0:false, 1:true, -1:not applicable
// compute the top and bottom vectors for the next column
for (int y = topY; y >= bottomY; y--)
{
int tx = lPos.x, ty = lPos.y;
// compute the coordinates of the tile at the top of the column
switch (octant)
{
case 0: tx += x; ty -= y; break;
case 1: tx += y; ty -= x; break;
case 2: tx -= y; ty -= x; break;
case 3: tx -= x; ty -= y; break;
case 4: tx -= x; ty += y; break;
case 5: tx -= y; ty += x; break;
case 6: tx += y; ty += x; break;
case 7: tx += x; ty += y; break;
}
Vector3Int pos = new Vector3Int(tx, ty, 0); // the position of the tile at the top of the column
TileCompute(pos, fogMap, isPlayer, fov);
// NOTE: use the next line instead if you want the algorithm to be symmetrical
if (isSymmetrical)
{
if ((y != topY || top.Y * x >= top.X * y) && (y != bottomY || bottom.Y * x <= bottom.X * y))
{
TileCompute(pos, fogMap, isPlayer, fov);
}
}
bool isOpaque = obstacleMap.GetTile(pos) != null;
if (x != rangeLimit)
{
if (isOpaque)
{
if (wasOpaque == 0) // if we found a transition from clear to opaque, this sector is done in this column, so
{ // adjust the bottom vector upwards and continue processing it in the next column.
Slope newBottom = new Slope(y * 2 + 1, x * 2 - 1); // (x*2-1, y*2+1) is a vector to the top-left of the opaque tile
if (y == bottomY)
{
bottom = newBottom; break;
} // don't recurse unless we have to
else
{
Compute(octant, lPos, rangeLimit, x + 1, top, newBottom, obstacleMap, fogMap, isPlayer, fov, isSymmetrical);
}
}
wasOpaque = 1;
}
else // adjust top vector downwards and continue if we found a transition from opaque to clear
{ // (x*2+1, y*2+1) is the top-right corner of the clear tile (i.e. the bottom-right of the opaque tile)
if (wasOpaque > 0)
{
top = new Slope(y * 2 + 1, x * 2 + 1);
}
wasOpaque = 0;
}
}
}
if (wasOpaque != 0)
{
break; // if the column ended in a clear tile, continue processing the current sector
}
}
}
/// <summary> Set the fog of war for a given tile. </summary>
static public void TileCompute(Vector3Int pos, Tilemap fogMap, bool isPlayer, FOV fov)
{
WorldTile tile;
if (!MapManager.instance.fogTiles.TryGetValue(pos, out tile))
{
return;
}
if (isPlayer)
{
fogMap.SetTileFlags(tile.localPlace, TileFlags.None);
fogMap.SetColor(tile.localPlace, new Color(1.0f, 1.0f, 1.0f, 0f));
tile.isVisible = true;
tile.isExplored = true;
}
if (!fov.VisibleTiles.Contains(pos))
{
fov.VisibleTiles.Add(pos);
}
}