Epic/mods/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.

-- Modifications by gpcf
-- 2018-12-09
-- get shot down while flying over protected areas marked as no-fly-zones (flak, from German Flugabwehrkanone)
--  set these areas with the /area_flak command

-- Modifications by SpaghettiToastBook
-- 2018-12-29
-- Physics overrides use player_monoids mod if available

local HUD_Overlay = true --show glider struts as overlay on HUD
local debug = false --show debug info in top-center of hud
hangglider = {} --Make this global, so other mods can tell if hangglider exists.
hangglider.use = {}
hangglider.players = {}

if HUD_Overlay then
   hangglider.id = {}  -- hud id for displaying overlay with struts
end

if debug then
   hangglider.debug = {} -- hud id for debug data
end

local physics_attrs = {"jump", "speed", "gravity"}

local function apply_physics_override(player, overrides)
   player:set_physics_override(overrides)
end

local function remove_physics_override(player, overrides)
   for _, attr in pairs(physics_attrs) do
      if overrides[attr] then
         player:set_physics_override({[attr] = 1})
      end
   end
end

local step_v
minetest.register_entity("hangglider:glider", {
   visual = "mesh",
   visual_size = {x = 12, y = 12},
   collisionbox = {0,0,0,0,0,0},
   mesh = "glider.obj",
   immortal = true,
   static_save = false,
   textures = {"wool.png","default_wood.png"},
   on_step = function(self, dtime)
      local canExist = false
      if self.object:get_attach() then
         local player = self.object:get_attach("parent")
         if player then
            local pos = player:get_pos()
            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 ~= "none") then
                     canExist = true
                     step_v = player:get_velocity().y
                     if step_v < 0 and step_v > -3 then
                        apply_physics_override(player, {speed=math.abs(step_v/2) + 0.75})
                     elseif step_v <= -3 then --Cap our gliding movement speed.
                        apply_physics_override(player, {speed=2.25})
                     else
                        remove_physics_override(player, {speed=1})
                     end
                     if debug then player:hud_change(hangglider.debug[pname].id, "text", step_v..', '..player:get_physics_override().gravity..', '..tostring(hangglider.airbreak[pname])) end
                     apply_physics_override(player, {gravity=((step_v + 3)/20)})
                  end
                     --[[local vel = player:get_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
            if not canExist then --Landed, reset player physics and stuff.
               hangglider.use[pname] = false
               armor:set_player_armor(player)
               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)
   remove_physics_override(player, {
      gravity = 1,
      jump = 1,
   })
   hangglider.use[player:get_player_name()] = false
end)

minetest.register_on_joinplayer(function(player)
   local pname = player:get_player_name()
   remove_physics_override(player, {
      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()
      hangglider.players[pname] = player:get_physics_override()
      if 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_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
            minetest.add_entity(pos, "hangglider:glider"):set_attach(player, "", {x=0,y=10,z=0}, {x=0,y=0,z=0})
         end
         hangglider.use[pname] = true
         apply_physics_override(player, {jump = 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"},
})