Improved Boids and Context Steering

boids.lua

@@ -3,7 +3,18 @@
 -----------
 
 local abs = math.abs
-local random = math.random
+local atan2 = math.atan2
+local sin = math.sin
+local cos = math.cos
+
+local function average_angle(tbl)
+	local sum_sin, sum_cos = 0, 0
+	for _, v in pairs(tbl) do
+		sum_sin = sum_sin + sin(v)
+		sum_cos = sum_cos + cos(v)
+	end
+	return atan2(sum_sin, sum_cos)
+end
 
 local function average(tbl)
 	local sum = 0
@@ -13,20 +24,17 @@ local function average(tbl)
 	return sum / #tbl
 end
 
-local function average_angle(tbl)
-	local sum_sin, sum_cos = 0, 0
-	for _, v in pairs(tbl) do
-		sum_sin = sum_sin + math.sin(v)
-		sum_cos = sum_cos + math.cos(v)
-	end
-	return math.atan2(sum_sin, sum_cos)
+local function interp_rad(a, b, w)
+	local cs = (1 - w) * cos(a) + w * cos(b)
+	local sn = (1 - w) * sin(a) + w * sin(b)
+	return atan2(sn, cs)
 end
 
-local vec_dist = vector.distance
-local vec_dir = vector.direction
 local vec_add = vector.add
-local vec_normal = vector.normalize
+local vec_dir = vector.direction
+local vec_dist = vector.distance
 local vec_divide = vector.divide
+local vec_normal = vector.normalize
 
 local function get_average_pos(vectors)
 	local sum = {x = 0, y = 0, z = 0}
@@ -53,13 +61,91 @@ local dir2yaw = minetest.dir_to_yaw
 
 -- Get Boid Members --
 
--- This function scans within
--- a set radius for potential
--- boid members, and assigns
--- a leader. A new leader
--- is only assigned every 12
--- seconds or if a new mob
--- is in the boid.
+function creatura.get_boid_cached(self)
+	local pos = self.object:get_pos()
+	if not pos then return end
+	local radius = self.tracking_range * 0.5 or 4
+	local members = self._movement_data.boids or {}
+	local max_boids = self.max_boids or 7
+	if #members > 0 then
+		for i = #members, 1, -1 do
+			local object = members[i]
+			if not object or not object:get_yaw() then members[i] = nil end
+		end
+		if #members >= max_boids then return members end
+	end
+	local objects = minetest.get_objects_inside_radius(pos, radius)
+	if #objects < 2 then return {} end
+	for _, object in ipairs(objects) do
+		local ent = object and object ~= self.object and object:get_luaentity()
+		if ent
+		and ent.name == self.name then
+			local move_data = ent._movement_data
+			if move_data
+			and (not move_data.boids
+			or #move_data.boids < max_boids) then
+				table.insert(members, object)
+			end
+		end
+		if #members >= max_boids then break end
+	end
+	self._movement_data.boids = members
+
+	return members
+end
+
+-- Calculate Boid Movement Direction
+
+function creatura.get_boid_dir(self)
+	local pos = self.object:get_pos()
+	if not pos then return end
+	local boids = creatura.get_boid_cached(self)
+	if #boids < 2 then return end
+	local pos_no, pos_sum = 0, {x = 0, y = 0, z = 0}
+	local sum_sin, sum_cos = 0, 0
+	local lift_no, lift_sum = 0, 0
+
+	local vel
+	local boid_pos
+	local closest_pos
+	for _, object in ipairs(boids) do
+		if object then
+			boid_pos, vel = object:get_pos(), object:get_velocity()
+			local obj_yaw = object:get_yaw()
+			pos_no, pos_sum = pos_no + 1, vec_add(pos_sum, boid_pos)
+			sum_sin, sum_cos = sum_sin + sin(obj_yaw), sum_cos + cos(obj_yaw)
+			lift_no, lift_sum = lift_no + 1, lift_sum + vel.y
+			if not closest_pos
+			or vec_dist(pos, boid_pos) < vec_dist(pos, closest_pos) then
+				closest_pos = boid_pos
+			end
+		end
+	end
+	if not closest_pos then return end
+	local center = vec_divide(pos_sum, pos_no)
+	local lift = lift_sum / lift_no
+
+	local angle_sin, angle_cos
+	local radius = self.tracking_range * 0.5 or 4
+	local dist_factor = (radius - vec_dist(pos, closest_pos)) / radius
+
+	local alignment = atan2(sum_sin, sum_cos)
+	local seperation = dir2yaw(vec_dir(closest_pos, pos))
+	local cohesion = dir2yaw(vec_dir(pos, center))
+	if dist_factor > 0.9 then
+		seperation = interp_rad(alignment, seperation, 0.5)
+		angle_sin, angle_cos = sin(seperation), cos(seperation)
+	else
+		angle_sin, angle_cos = sin(cohesion), cos(cohesion)
+	end
+	local angle = atan2(angle_sin + sin(alignment), angle_cos + cos(alignment))
+
+	local dir = yaw2dir(angle)
+	dir.y = lift
+	return vector.normalize(dir), boids
+end
+
+-- Deprecated
 
 function creatura.get_boid_members(pos, radius, name)
 	local objects = minetest.get_objects_inside_radius(pos, radius)
@@ -71,7 +157,6 @@ function creatura.get_boid_members(pos, radius, name)
 		local object = objects[i]
 		if object:get_luaentity()
 		and object:get_luaentity().name == name then
-			object:get_luaentity().boid_heading = math.rad(random(360))
 			table.insert(members, object)
 		end
 	end
@@ -86,8 +171,6 @@ function creatura.get_boid_members(pos, radius, name)
 	return members
 end
 
--- Calculate Boid angles and offsets.
-
 function creatura.get_boid_angle(self, _boids, range)
 	local pos = self.object:get_pos()
 	local boids = _boids or creatura.get_boid_members(pos, range or 4, self.name)
@@ -127,9 +210,6 @@ function creatura.get_boid_angle(self, _boids, range)
 	local seperation = yaw + -(dir2yaw(dir2closest) - yaw)
 	local cohesion = dir2yaw(dir2center)
 	local params = {alignment}
-	if self.boid_heading then
-		table.insert(params, yaw + self.boid_heading)
-	end
 	if dist_2d(pos, closest_pos) < (self.boid_seperation or self.width * 3) then
 		table.insert(params, seperation)
 	elseif dist_2d(pos, center) > (#boids * 0.33) * (self.boid_seperation or self.width * 3) then
@@ -145,6 +225,5 @@ function creatura.get_boid_angle(self, _boids, range)
 	elseif math.abs(pos.y - closest_pos.y) > 1.5 * (self.boid_seperation or self.width * 3) then
 		table.insert(vert_params, vert_cohesion + (lift - vert_cohesion) * 0.1)
 	end
-	self.boid_heading = nil
 	return average_angle(params), average(vert_params)
 end