Method visible

src/Battlescape/TileEngine.cpp:388–444

* Checks for an opposing unit on this tile. * @param currentUnit The watcher. * @param tile The tile to check for * @return True if visible. */

 * @return True if visible.
 */
bool TileEngine::visible(BattleUnit *currentUnit, Tile *tile)
{
	// if there is no tile or no unit, we can't see it
	if (!tile || !tile->getUnit())
	{
		return false;
	}

	// aliens can see in the dark, xcom can see at a distance of 9 or less, further if there's enough light.
	if (currentUnit->getFaction() == FACTION_PLAYER &&
		distance(currentUnit->getPosition(), tile->getPosition()) > 9 &&
		tile->getShade() > MAX_DARKNESS_TO_SEE_UNITS)
	{
		return false;
	}

	if (currentUnit->getFaction() == tile->getUnit()->getFaction()) return true; // friendlies are always seen

	Position originVoxel = getSightOriginVoxel(currentUnit);

	bool unitSeen = false;
	// for large units origin voxel is in the middle

	Position scanVoxel;
	std::vector<Position> _trajectory;
	unitSeen = canTargetUnit(&originVoxel, tile, &scanVoxel, currentUnit);

	if (unitSeen)
	{
		// now check if we really see it taking into account smoke tiles
		// initial smoke "density" of a smoke grenade is around 15 per tile
		// we do density/3 to get the decay of visibility
		// so in fresh smoke we should only have 4 tiles of visibility
		// this is traced in voxel space, with smoke affecting visibility every step of the way
		_trajectory.clear();
		calculateLine(originVoxel, scanVoxel, true, &_trajectory, currentUnit);
		Tile *t = _save->getTile(currentUnit->getPosition());
		size_t visibleDistance = _trajectory.size();
		for (size_t i = 0; i < _trajectory.size(); i++)
		{
			if (t != _save->getTile(Position(_trajectory.at(i).x/16,_trajectory.at(i).y/16, _trajectory.at(i).z/24)))
			{
				t = _save->getTile(Position(_trajectory.at(i).x/16,_trajectory.at(i).y/16, _trajectory.at(i).z/24));
			}
			if (t->getFire() == 0)
			{
				visibleDistance += t->getSmoke() / 3;
			}
			if (visibleDistance > MAX_VOXEL_VIEW_DISTANCE)
			{
				unitSeen = false;
				break;
			}
		}
	}
	return unitSeen;
}