The love physics library is very flexible, but doing relatively simple things with it can be tedious. A good solution is the windfield library, but a few things didn’t quite sit right for me.
I’ve used windfield for a few practice projects, and I liked it very much. It makes protoyping faster, and massively reduces the time and mental effort spent putting together all the pieces of love.physics. so far however, I’ve encountered the occaisional issue that was tricky to track down due to (in particular) the collision-management system in place in windfield. When I needed to modify parts of it to my purposes, I found its size and complexity made it take a little longer than it could have with a simpler library.
Breezefield is a lightweight alternative that takes the parts that I liked best about windfield and leaves out what I felt held it back.
world:newCollider(<shape_type>, <shape_args>, <table_to_use>(optional))
or
bf.Collider.new(<shape_type>, <shape_args>)
world:queryRectangleArea(x1, y1, x2, y2)
Collider:<methodname> (e.g. get/setRestitution, get/setX, etc...)
World:<methodname> (e.g. update)
world:draw()
Just redefine :draw on your collider objects, add other objects with :draw methods to world.colliders.
Call world:draw(<alpha>, true) to draw physics boundaries in addition to self-defined :draw methods
World._physworld contains the regular love.physics.world object. Collider.fixture, Collider.body, Collider.shape all contain the respective physics objects
if there are any issues in breezefields implementation that complicates using love.physics together with it, let me know, or better yet, send a pull request
I reccomend you ensure you understand love.physics, as breezefield mostly just wraps that. You can start here. To install simply clone or download the repository and place breezefield anywhere in your lua path or in your project directory.
bf = require("breezefield")
function love.load()
world = bf.newWorld(0, 90.81, true)
-- bf.World:new also works
-- any function of love.physics.world should work on World
print(world:getGravity())
ground = bf.Collider.new(world, "Polygon",
{0, 550, 650, 550 , 650, 650, 0, 650})
ground:setType("static")
ball = bf.Collider.new(world, "Circle", 325, 325, 20)
ball:setRestitution(0.8) -- any function of shape/body/fixture works
block1 = bf.Collider.new(world, "Polygon", {150, 375, 250, 375,
250, 425, 150, 425})
end
any functions for shape, body, or fixture work on Colliders
function love.update(dt)
world:update(dt)
if love.keyboard.isDown("right") then
ball:applyForce(400, 0)
elseif love.keyboard.isDown("left") then
ball:applyForce(-400, 0)
elseif love.keyboard.isDown("up") then
ball:setPosition(325, 325)
ball:setLinearVelocity(0, 0)
elseif love.keyboard.isDown("down") then
ball:applyForce(0, 600)
end
end
function love.draw()
world:draw()
end
default collision callbacks of World will locate the colliders from a fixture’s userData and call the relevant :enter :exit :postSolve or :preSolve method
little_ball = {}
little_ball.__index = little_ball
setmetatable(little_ball, bf.Collider) -- this is important
-- otherwise setting the new object's metatable to little_ball overwrites
function spawn_random_ball()
little_ball.new(love.math.random(love.graphics.getWidth()), 0)
end
function little_ball.new(x, y)
local n = bf.Collider.new(world, 'Circle', x, y, 5)
setmetatable(n, little_ball)
return n
end
one feature is that any function callbacks returned by Collider:enter/exit/<post/pre>Solve are run in world:update() this lets us easily create and destroy objects in collision callbacks without crashing Box2D (love.physics’s backend)
function ball:postSolve(other)
if other == block1 then
-- creating Collder.new should never be called inside a callback
-- a limitation of (box2d)
-- instead, return a function to be called during World:update()
return spawn_random_ball -- see above for definition
end
end
simply define the :draw function on your collider (you can still access the default draw as :__draw__)
function little_ball:draw(alpha)
love.graphics.setColor(0.9, 0.9, 0.0)
love.graphics.circle('fill', self:getX(), self:getY(), self:getRadius())
end
function love.mousepressed()
local x, y
local radius = 30
x, y = love.mouse.getPosition()
local colls = world:queryCircleArea(x, y, radius)
for _, collider in ipairs(colls) do
if collider.identity == little_ball then
local dx = love.mouse.getX() - collider:getX()
local dy = love.mouse.getY() - collider:getY()
local power = -5
collider:applyLinearImpulse(power * dx, power * dy)
end
end
end
and after little_ball’s declaration
little_ball.identity = little_ball
for now, see: https://love2d.org/wiki/Contact:setEnabled https://love2d.org/wiki/Fixture:setFilterData
https://love2d.org/forums/viewtopic.php?f=5&t=86113&p=224718#p224718