Line_of_sight: Improve using VoxelLineIterator

This commit rewrites line_of_sight with VoxelLineIterator.
Stepsize is no longer needed, the results will be always accurate.

doc/lua_api.txt

@@ -2876,13 +2876,12 @@ and `minetest.auth_reload` call the authentication handler.
    *   parameter was absent)
* `minetest.delete_area(pos1, pos2)`
    * delete all mapblocks in the area from pos1 to pos2, inclusive
* `minetest.line_of_sight(pos1, pos2, stepsize)`: returns `boolean, pos`
    * Check if there is a direct line of sight between `pos1` and `pos2`
* `minetest.line_of_sight(pos1, pos2)`: returns `boolean, pos`
    * Checks if there is anything other than air between pos1 and pos2.
    * Returns false if something is blocking the sight.
    * Returns the position of the blocking node when `false`
    * `pos1`: First position
    * `pos2`: Second position
    * `stepsize`: smaller gives more accurate results but requires more computing
      time. Default is `1`.
* `minetest.raycast(pos1, pos2, objects, liquids)`: returns `Raycast`
    * Creates a `Raycast` object.
    * `pos1`: start of the ray

src/script/lua_api/l_env.cpp

@@ -966,24 +966,19 @@ int ModApiEnvMod::l_clear_objects(lua_State *L)
	return 0;
}

// line_of_sight(pos1, pos2, stepsize) -> true/false, pos
// line_of_sight(pos1, pos2) -> true/false, pos
int ModApiEnvMod::l_line_of_sight(lua_State *L)
{
	float stepsize = 1.0;

	GET_ENV_PTR;

	// read position 1 from lua
	v3f pos1 = checkFloatPos(L, 1);
	// read position 2 from lua
	v3f pos2 = checkFloatPos(L, 2);
	//read step size from lua
	if (lua_isnumber(L, 3)) {
		stepsize = lua_tonumber(L, 3);
	}

	v3s16 p;
	bool success = env->line_of_sight(pos1, pos2, stepsize, &p);

	bool success = env->line_of_sight(pos1, pos2, &p);
	lua_pushboolean(L, success);
	if (!success) {
		push_v3s16(L, p);

src/script/lua_api/l_env.h

@@ -156,7 +156,7 @@ class ModApiEnvMod : public ModApiBase {
	// spawn_tree(pos, treedef)
	static int l_spawn_tree(lua_State *L);

	// line_of_sight(pos1, pos2, stepsize) -> true/false
	// line_of_sight(pos1, pos2) -> true/false
	static int l_line_of_sight(lua_State *L);

	// raycast(pos1, pos2, objects, liquids) -> Raycast

src/serverenvironment.cpp

@@ -489,30 +489,21 @@ bool ServerEnvironment::removePlayerFromDatabase(const std::string &name)
	return m_player_database->removePlayer(name);
}

bool ServerEnvironment::line_of_sight(v3f pos1, v3f pos2, float stepsize, v3s16 *p)
bool ServerEnvironment::line_of_sight(v3f pos1, v3f pos2, v3s16 *p)
{
	float distance = pos1.getDistanceFrom(pos2);

	//calculate normalized direction vector
	v3f normalized_vector = v3f((pos2.X - pos1.X)/distance,
		(pos2.Y - pos1.Y)/distance,
		(pos2.Z - pos1.Z)/distance);

	//find out if there's a node on path between pos1 and pos2
	for (float i = 1; i < distance; i += stepsize) {
		v3s16 pos = floatToInt(v3f(normalized_vector.X * i,
			normalized_vector.Y * i,
			normalized_vector.Z * i) +pos1,BS);

		MapNode n = getMap().getNodeNoEx(pos);

		if(n.param0 != CONTENT_AIR) {
			if (p) {
				*p = pos;
			}
	// Iterate trough nodes on the line
	voxalgo::VoxelLineIterator iterator(pos1 / BS, (pos2 - pos1) / BS);
	do {
		MapNode n = getMap().getNodeNoEx(iterator.m_current_node_pos);

		// Return non-air
		if (n.param0 != CONTENT_AIR) {
			if (p)
				*p = iterator.m_current_node_pos;
			return false;
		}
	}
		iterator.next();
	} while (iterator.m_current_index <= iterator.m_last_index);
	return true;
}

src/serverenvironment.h

@@ -328,8 +328,15 @@ class ServerEnvironment : public Environment
	// This makes stuff happen
	void step(f32 dtime);

	//check if there's a line of sight between two positions
	bool line_of_sight(v3f pos1, v3f pos2, float stepsize=1.0, v3s16 *p=NULL);
	/*!
	 * Returns false if the given line intersects with a
	 * non-air node, true otherwise.
	 * \param pos1 start of the line
	 * \param pos2 end of the line
	 * \param p output, position of the first non-air node
	 * the line intersects
	 */
	bool line_of_sight(v3f pos1, v3f pos2, v3s16 *p = NULL);

	u32 getGameTime() const { return m_game_time; }