File:raycast example screenshot.png

function love.load()
    -- Setting this to 1 to avoid all current scaling bugs.
    love.physics.setMeter(1)

    World = love.physics.newWorld()

    Box = {}
    Box.Body = love.physics.newBody(World, 400, 300, "dynamic")
    Box.Shape = love.physics.newRectangleShape(150, 150)
    Box.Fixture = love.physics.newFixture(Box.Body, Box.Shape)

    -- Giving the box a gentle spin.
    Box.Body:setAngularVelocity(0.5)

    Ray1 = {
        point1 = {},
        point2 = {},
    }
    Ray1.point1.x, Ray1.point1.y = 50, 50
    Ray1.point2.x, Ray1.point2.y = 400, 300
    Ray1.scale = 1

    Ray2 = {
        point1 = {},
        point2 = {},
    }
    Ray2.point1.x, Ray2.point1.y = 500, 400
    Ray2.point2.x, Ray2.point2.y = Ray2.point1.x + math.cos(math.pi*1.45), Ray2.point1.y + math.sin(math.pi*1.45)
    Ray2.scale = 150
end

function love.update(dt)
    World:update(dt)
end

function love.draw()
    -- Drawing the box.
    love.graphics.setColor(255, 255, 255)
    love.graphics.polygon("line", Box.Body:getWorldPoints( Box.Shape:getPoints() ))

    -- Drawing the input lines of the rays and the reach of ray 2 in gray.
    love.graphics.setLineWidth(3)
    love.graphics.setColor(50, 50, 50)
    love.graphics.line(Ray2.point1.x, Ray2.point1.y, Ray2.point1.x + (Ray2.point2.x - Ray2.point1.x) * Ray2.scale, Ray2.point1.y + (Ray2.point2.y - Ray2.point1.y) * Ray2.scale)
    love.graphics.setColor(255, 255, 255)
    love.graphics.line(Ray1.point1.x, Ray1.point1.y, Ray1.point2.x, Ray1.point2.y)
    love.graphics.line(Ray2.point1.x, Ray2.point1.y, Ray2.point2.x, Ray2.point2.y)
    love.graphics.setLineWidth(1)

    -- Remember that the ray cast can return nil if it hits nothing.
    local r1nx, r1ny, r1f = Box.Fixture:rayCast(Ray1.point1.x, Ray1.point1.y, Ray1.point2.x, Ray1.point2.y, Ray1.scale)
    local r2nx, r2ny, r2f = Box.Fixture:rayCast(Ray2.point1.x, Ray2.point1.y, Ray2.point2.x, Ray2.point2.y, Ray2.scale)

    if r1nx then
        -- Calculating the world position where the ray hit.
        local r1HitX = Ray1.point1.x + (Ray1.point2.x - Ray1.point1.x) * r1f
        local r1HitY = Ray1.point1.y + (Ray1.point2.y - Ray1.point1.y) * r1f

        -- Drawing the ray from the starting point to the position on the shape.
        love.graphics.setColor(255, 0, 0)
        love.graphics.line(Ray1.point1.x, Ray1.point1.y, r1HitX, r1HitY)

        -- We also get the surface normal of the edge the ray hit. Here drawn in green
        love.graphics.setColor(0, 255, 0)
        love.graphics.line(r1HitX, r1HitY, r1HitX + r1nx * 25, r1HitY + r1ny * 25)
    end

    if r2nx then
        -- Calculating the world position where the ray hit.
        local r2HitX = Ray2.point1.x + (Ray2.point2.x - Ray2.point1.x) * r2f
        local r2HitY = Ray2.point1.y + (Ray2.point2.y - Ray2.point1.y) * r2f

        -- Drawing the ray from the starting point to the position on the shape.
        love.graphics.setColor(255, 0, 0)
        love.graphics.line(Ray2.point1.x, Ray2.point1.y, r2HitX, r2HitY)

        -- We also get the surface normal of the edge the ray hit. Here drawn in green
        love.graphics.setColor(0, 255, 0)
        love.graphics.line(r2HitX, r2HitY, r2HitX + r2nx * 25, r2HitY + r2ny * 25)
    end
end