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phys = {}
local world = {}
phys.world = world
world.boxes = {}
world.layers = {}
-- There are a few primary physics layers:
--
-- * Hard: for hard collisions that do not allow things in whatsoever
-- * Soft: for collisions that push other things away over time
-- * Player_Hurtbox: collision box that hurts the player
-- * Player_Hitbox: collision box from the player that damages things
-- * Enemy_Hurtbox: collision box that hurts enemies
-- * Enemy_Hitbox: collision box from an enemy that damages things
--
-- You can use whatever physics layer you want, but these are the standard ones
local function aabb(ax, ay, aw, ah, bx, by, bw, bh)
return
ax < bx + bw and bx < ax + aw and
ay < by + bh and by < ay + ah
end
local function add_box_to_layers(box)
for _, layer in ipairs(box.layers) do
if not world.layers[layer] then
world.layers[layer] = {}
end
table.insert(world.layers[layer], box)
end
end
phys.Box = {}
phys.Box.__index = phys.Box
function phys.Box.new(
x, y,
width, height,
opts
)
opts = opts or {}
local self = setmetatable({}, phys.Box)
self.x = x
self.y = y
self.offsetx = opts.offsetx or 0
self.offsety = opts.offsety or 0
self.width = width
self.height = height
self.layers = opts.layers or { "hard" }
self.mask = opts.mask or {}
self.touchx = 0
self.touchy = 0
add_box_to_layers(self)
return self
end
function phys.Box:touching_left()
return self.touchx < 0
end
function phys.Box:touching_right()
return self.touchx > 0
end
function phys.Box:touching_horizontal()
return self.touchx ~= 0
end
function phys.Box:touching_up()
return self.touchy < 0
end
function phys.Box:touching_down()
return self.touchy > 0
end
function phys.Box:touching_vertical()
return self.touchy ~= 0
end
function phys.Box:touching()
return self.touchx ~= 0 and self.touchy ~= 0
end
function phys.Box:get_rect()
return
self.x + self.offsetx,
self.y + self.offsety,
self.width,
self.height
end
function collision_check(box)
local box_x, box_y, box_width, box_height = box:get_rect()
local other_x, other_y, other_width, other_height
for _, layer in ipairs(box.mask) do
for _, other in ipairs(world.layers[layer] or {}) do
if other == box then
goto continue
end
other_x, other_y, other_width, other_height = other:get_rect()
if aabb(
box_x, box_y, box_width, box_height,
other_x, other_y, other_width, other_height
) then
return true
end
::continue::
end
end
return false
end
function phys.Box:update(velx, vely, dt)
local small_side = math.min(self.width, self.height)
local steps = math.ceil(vec_len(velx * dt, vely * dt) / small_side)
-- this block is fat. much like a certain croatian...
-- not anymore :D
for i = 1, steps do
local p = i / steps
local before
before = self.x
self.x = self.x + velx * dt * p
if collision_check(self) then
self.touchx = velx > 0 and 1 or -1
velx = 0
self.x = before
end
before = self.y
self.y = self.y + vely * dt * p
if collision_check(self) then
self.touchy = velx > 0 and 1 or -1
vely = 0
self.y = before
end
if self:touching() then
break
end
end
return velx, vely
end
function phys.Box:draw()
local x, y, w, h = self:get_rect()
lg.rectangle("line", x, y, w, h)
end
|
