Allow for spawning in the caves

Use the config file setting to turn on the option to spawn in the caves
by default, both upon joining as a new player and upon respawning after
death.

config.lua

@@ -25,6 +25,9 @@ setting("number", "ymin", -33000) --bottom realm limit
 setting("number", "ymax", -700) --top realm limit
 setting("number", "tcave", 0.5) --cave threshold
 
+--should player spawn in caves?
+setting("bool", "cavespawn", false)
+
 --falling icicles
 setting("bool", "falling_icicles", true) --enable/disable falling icicles
 setting("number", "fallcha", 0.33) --chance of icicles falling when dug

functions.lua

@@ -383,4 +383,170 @@ function caverealms:legacy_giant_shroom(x, y, z, area, data) --leftovers :P
 			end
 		end
 	end
-end
\ No newline at end of file
+end
+
+-- Experimental and very geometric function to create giant octagonal crystals in a variety of random directions
+-- Uses calculations for points on a sphere, lines in geometric space
+function caverealms:giant_shroom(x, y, z, area, data)
+	--Grab content id's... diamond is a placeholder
+	local c_crys = minetest.get_content_id("default:diamondblock")
+	
+	local MAX_LEN = 25 --placeholder for a config file constant
+	local MIN_LEN = 10 --ditto
+	
+	local target = {x=0, y=MAX_LEN, z=0} -- 3D space coordinate of the crystal's endpoint
+	
+	local length = math.random(MIN_LEN, MAX_LEN) --get a random length for the crystal
+	local dir1 = math.random(0, 359) -- Random direction in degrees around a circle
+	local dir2 = math.random(0, 180) -- Random direction in a semicircle, for 3D location
+	
+	--OK, so now make a 3D point out of those spherical coordinates...
+	target.x = math.ceil(length * math.cos(dir1 * 3.14/180)) --Round it up to make sure it's a nice integer for the coordinate system
+	target.z = math.ceil(length * math.sin(dir1 * 3.14/180))
+	--Y is also simple, just use dir2.  Note that, due to how these calculations are carried out, this is not a coordinate on a perfect sphere. This is OK for our purposes.
+	target.y = math.ceil(length * math.sin(dir2 * 3.14/180))
+	
+	-- Now, determine if the crystal should go up or down, based on where it is
+	if (caverealms:above_solid(x,y,z,area,data)) then
+		target.y = target.y * -1
+	end
+	
+	--Bring the coordinates near the area you're generating
+	target.x = target.x + x
+	target.y = target.y + y
+	target.z = target.z + z
+	
+	
+end
+
+local CAVESPAWN = caverealms.config.cavespawn --false by default.  Change to true in order to spawn in the caves when joining as a new player or respawning after death
+local spawned = false;
+local ydepth = -960;
+
+if (CAVESPAWN) then
+	minetest.register_on_newplayer(function(player)
+		while spawned ~= true do
+			player:setpos({x=0,y=ydepth,z=0})
+			--minetest.after(2, function(player, ydepth)
+				spawnplayer(player, ydepth)
+			--end, player, ydepth)
+			ydepth = ydepth - 80
+		end
+	end)
+
+	minetest.register_on_respawnplayer(function(player)
+		while spawned ~= true do
+			player:setpos({x=0,y=ydepth,z=0})
+			--minetest.after(2, function(player, ydepth)
+				spawnplayer(player, ydepth)
+			--end, player, ydepth)
+			ydepth = ydepth - 80
+		end
+		return true
+	end)
+end
+
+-- Spawn player underground
+function spawnplayer(player, ydepth)
+	
+	local xsp
+	local ysp
+	local zsp
+	-- 3D noise for caves
+
+	local np_cave = {
+		offset = 0,
+		scale = 1,
+		spread = {x=512, y=256, z=512}, -- squashed 2:1
+		seed = 59033,
+		octaves = 6,
+		persist = 0.63
+	}
+
+	-- 3D noise for wave
+
+	local np_wave = {
+		offset = 0,
+		scale = 1,
+		spread = {x=256, y=256, z=256},
+		seed = -400000000089,
+		octaves = 3,
+		persist = 0.67
+	}
+	
+	local YMIN = caverealms.config.ymin -- Approximate realm limits.
+	local YMAX = caverealms.config.ymax
+	local TCAVE = caverealms.config.tcave --0.5 -- Cave threshold. 1 = small rare caves, 0.5 = 1/3rd ground volume, 0 = 1/2 ground volume
+	local BLEND = 128 -- Cave blend distance near YMIN, YMAX
+	
+	local yblmin = YMIN + BLEND * 1.5
+	local yblmax = YMAX - BLEND * 1.5
+	
+	for chunk = 1, 64 do
+		print ("[caverealms] searching for spawn "..chunk)
+		local x0 = 80 * math.random(-32, 32) - 32
+		local z0 = 80 * math.random(-32, 32) - 32
+		local y0 = ydepth-32
+		local x1 = x0 + 79
+		local z1 = z0 + 79
+		local y1 = ydepth+47
+
+		local sidelen = 80
+		local chulens = {x=sidelen, y=sidelen, z=sidelen}
+		local minposxyz = {x=x0, y=y0, z=z0}
+		local minposxz = {x=x0, y=z0}
+
+		local nvals_cave = minetest.get_perlin_map(np_cave, chulens):get3dMap_flat(minposxyz) --cave noise for structure
+		local nvals_wave = minetest.get_perlin_map(np_wave, chulens):get3dMap_flat(minposxyz) --wavy structure of cavern ceilings and floors
+
+		local nixz = 1
+		local nixyz = 1
+		for z = z0, z1 do
+			for y = y0, y1 do
+				for x = x0, x1 do
+					local n_abscave = math.abs(nvals_cave[nixyz])
+					local n_abswave = math.abs(nvals_wave[nixyz])
+					
+					local tcave --declare variable
+					--determine the overal cave threshold
+					if y < yblmin then
+						tcave = TCAVE + ((yblmin - y) / BLEND) ^ 2
+					elseif y > yblmax then
+						tcave = TCAVE + ((y - yblmax) / BLEND) ^ 2
+					else
+						tcave = TCAVE
+					end
+					
+					--if y >= 1 and density > -0.01 and density < 0 then
+					if (nvals_cave[nixyz] + nvals_wave[nixyz])/2 > tcave + 0.005 and (nvals_cave[nixyz] + nvals_wave[nixyz])/2 < tcave + 0.015 then --if node falls within cave threshold
+						ysp = y + 1
+						xsp = x
+						zsp = z
+						break
+					end
+					nixz = nixz + 1
+					nixyz = nixyz + 1
+				end
+				if ysp then
+					break
+				end
+				nixz = nixz - 80
+			end
+			if ysp then
+				break
+			end
+			nixz = nixz + 80
+		end
+		if ysp then
+			break
+		end
+	end
+	print ("[caverealms] spawn player ("..xsp.." "..ysp.." "..zsp..")")
+	player:setpos({x=xsp, y=ysp, z=zsp})
+	spawned = true
+end
+
+--minetest.register_on_newplayer(function(player)
+	--spawnplayer(player)
+--end)
+