hangglider/init.lua

-- Hangglider mod for Minetest
-- Original code by Piezo_ (orderofthefourthwall@gmail.com)
-- 2018-11-14

-- Modifications by David G (kestral246@gmail.com)
-- 2018-11-24
-- For Minetest 5.x, glider's set_attach needs to be offset by 1 node
--     Switch to alternate commented line below with correct offset.
-- Additional tuning of parameters.
-- Commented out debug hud display code, prefixed with "--debug:".

-- 2018-11-22
-- Give visual indication that hangglider is equiped.
--     Display simple overlay with blurred struts when equiped.
--     Issue: don't know how to disable overlay in third person view.
-- Also Unequip hangglider when landing on water.
-- Attempt to linearize parabolic flight path.
--     Start gravity stronger, but gradually reduce it as descent velocity increases.
--     Don't use airstopper when equipped from the ground (descent velocity is low).
--     Slightly increase flight speed to 1.25.
-- Unequip/equip cycling mid-flight should not fly farther than continuous flight.
--     When equipping mid-air (descent velocity higher), use airstopper but increase descent slope afterwards.
--     Create airbreak flag so all equips mid-flight use faster descent.
--     Reset airbreak flag only when land (canExist goes false).
--     Issue: it wouldn't reset if land in water, use fly, and launch from air, before I added test for water,
--            not sure if there are other such cases.
-- Temporarily add hud debug display to show descent velocity, gravity override, and airbreak flag.
--     Still in process of tuning all the parameters.


-- Modifications by Piezo_
-- 2018-11-25
-- hud overlay and debug can be enabled/disabled
-- Added blender-rendered overlay for struts using the actual model.
-- Reduced airbreak penalty severity
-- gave glider limited durability.
-- Improved gravity adjustment function.
-- Changed airbreaking process 
-- Removed airbreak penalty, as any 'advantage' seems minimal after new adjustments
-- Removed airbreak until minetest devs are smart enough to implement better serverside players.
-- Simplified liquid check.

local HUD_Overlay = true --show glider struts as overlay on HUD
local debug = false --show debug info in top-center of hud
local moveModelUp = false
if tonumber(string.sub(minetest.get_version().string, 1, 1)) and tonumber(string.sub(minetest.get_version().string, 1, 1)) > 4 then
	moveModelUp = true
end
hangglider = {} --Make this global, so other mods can tell if hangglider exists.
hangglider.use = {}
if HUD_Overlay then
hangglider.id = {}  -- hud id for displaying overlay with struts
end
if debug then  hangglider.debug = {} end -- hud id for debug data
--hangglider.airbreak = {}  -- true if falling fast when equip
--[[
minetest.register_entity("hangglider:airstopper", { --A one-instant entity that catches the player and stops them.
	is_visible = false,
	physical = false,
	immortal = true,
	attach = nil,
	on_step = function(self, _)
		local canExist = false
		if self.attach then
			local player = self.attach
			if player:is_player() then
				local pname = player:get_player_name()
				canExist = true
				if player:get_player_velocity().y < 0.5 and player:get_player_velocity().y > -0.5 then 
					--Let go when the player actually stops, as that's the whole point.
					if hangglider.use[pname] then
						if moveModelUp then
							minetest.add_entity(player:get_pos(), "hangglider:glider"):set_attach(player, "", {x=0,y=10,z=0}, {x=0,y=0,z=0})
						else
							minetest.add_entity(player:get_pos(), "hangglider:glider"):set_attach(player, "", {x=0,y=0,z=0}, {x=0,y=0,z=0})
						end
					end
					canExist = false
				end
			end
			if not canExist then
				player:set_detach()
			end
		end
		if not canExist then
			self.object:remove()
		end
	end
})]]

if minetestd and minetestd.services.gravityctl.enabled then
minetestd.gravityctl.register_gravity_effect("hangglider", 
	function(player) 
		return hangglider.use[player:get_player_name()] 
	end,
	function(gravity, player) 
		local vel = player:get_player_velocity()
		if debug then player:hud_change(hangglider.debug[pname].id, "text", vel.y..', '..player:get_physics_override().gravity..', '..tostring(hangglider.airbreak[pname])) end
		return ((vel.y + 3)/20)
	end,
	7,
	1000
)
end

local step_v
minetest.register_entity("hangglider:glider", {
	visual = "mesh",
	visual_size = {x = 12, y = 12},
	mesh = "glider.obj",
	immortal = true,
	static_save = false,
	textures = {"wool_white.png","default_wood.png"},
	on_step = function(self, _)
		local canExist = false
		if self.object:get_attach() then
			local player = self.object:get_attach("parent")
			if player then
				local pos = player:getpos()
				local pname = player:get_player_name()
				if hangglider.use[pname] then
					local mrn_name = minetest.registered_nodes[minetest.get_node(vector.new(pos.x, pos.y-0.5, pos.z)).name]
					if mrn_name then
						if not (mrn_name.walkable or mrn_name.liquidtype) then
							canExist = true
							step_v = player:get_player_velocity().y
							if step_v < 0 and step_v > -3 then
								player:set_physics_override({speed=math.abs(step_v/2) + 0.75})
							elseif step_v <= -3 then --Cap our fall speed.
								player:set_physics_override({speed=2.25})
							else
								player:set_physics_override({speed=1})
							end
							if not minetestd then
								if debug then player:hud_change(hangglider.debug[pname].id, "text", step_v..', '..player:get_physics_override().gravity..', '..tostring(hangglider.airbreak[pname])) end
								player:set_physics_override({gravity=((step_v + 3)/20)})
							end
							--[[local vel = player:get_player_velocity()
							if debug then player:hud_change(hangglider.debug[pname].id, "text", vel.y..', '..grav..', '..tostring(hangglider.airbreak[pname])) end
							
							player:set_physics_override({gravity = (vel.y + 2.0)/20})
						]]end
					end
				end
				if not canExist then
					player:set_physics_override({
						jump = 1,
						speed = 1,
					})
					if not minetestd then
						player:set_physics_override({gravity=1})
					end
					hangglider.use[pname] = false
					if HUD_Overlay then
					player:hud_change(hangglider.id[pname], "text", "blank.png")
					end
					--hangglider.airbreak[pname] = false
				end
			end
		end
		if not canExist then 
			self.object:set_detach()
			self.object:remove() 
		end
	end
})

minetest.register_on_dieplayer(function(player)
	player:set_physics_override({
		gravity = 1,
		jump = 1,
	})
	hangglider.use[player:get_player_name()] = false
end)


minetest.register_on_joinplayer(function(player)
	local pname = player:get_player_name()
	player:set_physics_override({
		gravity = 1,
		jump = 1,
	})
	hangglider.use[pname] = false
	if HUD_Overlay then
	hangglider.id[pname] = player:hud_add({
		hud_elem_type = "image",
		text = "blank.png",
		position = {x=0, y=0},
		scale = {x=-100, y=-100},
		alignment = {x=1, y=1},
		offset = {x=0, y=0}
	}) end
	if debug then 
		hangglider.debug[pname] = {id = player:hud_add({hud_elem_type = "text",
			position = {x=0.5, y=0.1},
			text = "-",
			number = 0xFF0000}),  -- red text
			-- ht = {50,50,50},
		}
	end
	--hangglider.airbreak[pname] = false
end)

minetest.register_on_leaveplayer(function(player)
	local pname = player:get_player_name()
	hangglider.use[pname] = nil
	if HUD_Overlay then hangglider.id[pname] = nil end
	if debug then hangglider.debug[pname] = nil end
	--hangglider.airbreak[pname] = nil
end)

minetest.register_tool("hangglider:hangglider", {
	description = "Glider",
	inventory_image = "glider_item.png",
	stack_max=1,
	on_use = function(itemstack, player, pointed_thing)
		if not player then
			return
		end
		local pos = player:get_pos()
		local pname = player:get_player_name()
		if minetest.get_node(pos).name == "air" and not hangglider.use[pname] then --Equip
			minetest.sound_play("bedsheet", {pos=pos, max_hear_distance = 8, gain = 1.0})
			if HUD_Overlay then player:hud_change(hangglider.id[pname], "text", "glider_struts.png") end
			local airbreak = false
			local vel = player:get_player_velocity().y
			--[[if vel < -1.5 then  -- engage mid-air, falling fast, so stop but ramp velocity more quickly
				--hangglider.airbreak[pname] = true
				airbreak = true
				local stopper = minetest.add_entity(pos, "hangglider:airstopper")
				minetest.after(0, function(stopper, player) --"Extreme Measures"
					stopper:set_pos(player:get_pos())
					stopper:get_luaentity().attach = player
					player:set_attach( stopper, "", {x=0,y=0,z=0}, {x=0,y=0,z=0})
				end, stopper, player)
			end]]
			if not airbreak then 
				if moveModelUp then
					minetest.add_entity(pos, "hangglider:glider"):set_attach(player, "", {x=0,y=10,z=0}, {x=0,y=0,z=0})
				else
					minetest.add_entity(pos, "hangglider:glider"):set_attach(player, "", {x=0,y=0,z=0}, {x=0,y=0,z=0})
				end
			end
			hangglider.use[pname] = true
			player:set_physics_override({jump = 0})
			-- if minetest 0.4.x use this:
			
			-- if minetest 5.x use this:
			-- minetest.add_entity(player:get_pos(), "hangglider:glider"):set_attach(player, "", {x=0,y=10,z=0}, {x=0,y=0,z=0})
			itemstack:set_wear(itemstack:get_wear() + 255)
			return itemstack
		elseif hangglider.use[pname] then --Unequip
			if HUD_Overlay then player:hud_change(hangglider.id[pname], "text", "default_wood.png^[colorize:#0000:255") end
			hangglider.use[pname] = false
		end
	end,
	sound = {breaks = "default_tool_breaks"},
})

minetest.register_craft({
	type = "shapeless",
	output = "hangglider:hangglider",
	recipe = {"default:paper", "default:paper", "default:paper", "default:paper", "hangglider:hangglider", "default:paper", "default:paper", "default:paper", "default:paper"},
})

minetest.register_craft({
	output = "hangglider:hangglider",
	recipe = {
		{"wool:white", "wool:white", "wool:white"},
		{"default:stick", "", "default:stick"},
		{"", "default:stick", ""},
	}
})