diff options
| -rw-r--r-- | src/magic.cc | 17 |
1 files changed, 9 insertions, 8 deletions
diff --git a/src/magic.cc b/src/magic.cc index c02e0f0..af8e031 100644 --- a/src/magic.cc +++ b/src/magic.cc @@ -903,22 +903,23 @@ int GetDirection(int dx, int dy){ } }else{ // NOTE(fusion): This function uses the approximate tangent value, avoiding - // floating point calculations, for whatever reason. The tangent is unique - // and odd in the interval (-PI/2, +PI/2). We also need to recall that the - // Y-axis is inverted in Tibia, so we need to negate `dy`. + // floating point calculations. The tangent is unique and odd in the interval + // (-PI/2, +PI/2) but since that only covers half the unit circle, we need to + // mirror results to the other half by comparing the sign of `dx`. The Y-axis + // is also inverted in Tibia, so we need to negate `dy`. constexpr int Tangent_67_5 = 618; // => 618 / 256 ~ 2.41 ~ tan(67.5 deg) constexpr int Tangent_22_5 = 106; // => 106 / 256 ~ 0.41 ~ tan(22.5 deg) int Tangent = (-dy * 256) / dx; // => (dy * 256) / dx ~ (dy / dx) * 256 if(Tangent >= Tangent_67_5){ - Result = DIRECTION_NORTH; + Result = (dx < 0) ? DIRECTION_SOUTH : DIRECTION_NORTH; }else if(Tangent >= Tangent_22_5){ - Result = (dx < 0) ? DIRECTION_NORTHWEST : DIRECTION_NORTHEAST; + Result = (dx < 0) ? DIRECTION_SOUTHWEST : DIRECTION_NORTHEAST; }else if(Tangent >= -Tangent_22_5){ - Result = (dx < 0) ? DIRECTION_WEST : DIRECTION_EAST; + Result = (dx < 0) ? DIRECTION_WEST : DIRECTION_EAST; }else if(Tangent >= -Tangent_67_5){ - Result = (dx < 0) ? DIRECTION_SOUTHWEST : DIRECTION_SOUTHEAST; + Result = (dx < 0) ? DIRECTION_NORTHWEST : DIRECTION_SOUTHEAST; }else{ - Result = DIRECTION_SOUTH; + Result = (dx < 0) ? DIRECTION_NORTH : DIRECTION_SOUTH; } } return Result; |