World:rayCast

Available since LÖVE 0.8.0
This method is not supported in earlier versions.

Casts a ray and calls a function for each fixtures it intersects.

Function

Synopsis

World:rayCast( x1, y1, x2, y2, callback )

Arguments

number x1
The x position of the starting point of the ray.
number y1
The y position of the starting point of the ray.
number x2
The x position of the end point of the ray.
number y2
The y position of the end point of the ray.
function callback
A function called for each fixture intersected by the ray. The function gets six arguments and should return a number as a control value. The intersection points fed into the function will be in an arbitrary order. If you wish to find the closest point of intersection, you'll need to do that yourself within the function. The easiest way to do that is by using the fraction value.

Returns

Nothing.

Callback

Synopsis

control = callback( fixture, x, y, xn, yn, fraction )

Arguments

Fixture fixture
The fixture intersecting the ray.
number x
The x position of the intersection point.
number y
The y position of the intersection point.
number xn
The x value of the surface normal vector of the shape edge.
number yn
The y value of the surface normal vector of the shape edge.
number fraction
The position of the intersection on the ray as a number from 0 to 1 (or even higher if the ray length was changed with the return value).

Returns

number control
The ray can be controlled with the return value. A positive value sets a new ray length where 1 is the default value. A value of 0 terminates the ray. If the callback function returns -1, the intersection gets ignored as if it didn't happen.

Notes

There is a bug in LÖVE 0.8.0 where the normal vector passed to the callback function gets scaled by love.physics.getMeter.

Examples

Casting a ray over some random shapes.

function worldRayCastCallback(fixture, x, y, xn, yn, fraction)
	local hit = {}
	hit.fixture = fixture
	hit.x, hit.y = x, y
	hit.xn, hit.yn = xn, yn
	hit.fraction = fraction
 
	table.insert(Ray.hitList, hit)
 
	return 1 -- Continues with ray cast through all shapes.
end
 
function createStuff()
	-- Cleaning up the previous stuff.
	for i = #Terrain.Stuff, 1, -1 do
		Terrain.Stuff[i].Fixture:destroy()
		Terrain.Stuff[i] = nil
	end
 
	-- Generates some random shapes.
	for i = 1, 30 do
		local p = {}
 
		p.x, p.y = math.random(100, 700), math.random(100, 500)
		local shapetype = math.random(3)
		if shapetype == 1 then
			local w, h, r = math.random() * 10 + 40, math.random() * 10 + 40, math.random() * math.pi * 2
			p.Shape = love.physics.newRectangleShape(p.x, p.y, w, h, r)
		elseif shapetype == 2 then
			local a = math.random() * math.pi * 2
			local x2, y2 = p.x + math.cos(a) * (math.random() * 30 + 20), p.y + math.sin(a) * (math.random() * 30 + 20)
			p.Shape = love.physics.newEdgeShape(p.x, p.y, x2, y2)
		else
			local r = math.random() * 40 + 10
			p.Shape = love.physics.newCircleShape(p.x, p.y, r)
		end
 
		p.Fixture = love.physics.newFixture(Terrain.Body, p.Shape)
 
		Terrain.Stuff[i] = p
	end
end
 
function love.keypressed()
	createStuff()
end
 
function love.load()
	-- Setting this to 1 to avoid all current scaling bugs.
	love.physics.setMeter(1)
 
	-- Start out with the same random stuff each start.
	math.randomseed(0xfacef00d)
 
	World = love.physics.newWorld()
 
	Terrain = {}
	Terrain.Body = love.physics.newBody(World, 0, 0, "static")
	Terrain.Stuff = {}
	createStuff()
 
	Ray = {
		x1 = 0,
		y1 = 0,
		x2 = 0,
		y2 = 0,
		hitList = {}
	}
end
 
function love.update(dt)
	local now = love.timer.getTime()
 
	World:update(dt)
 
	-- Clear fixture hit list.
	Ray.hitList = {}
 
	-- Calculate ray position.
	local pos = (math.sin(now/4) + 1.2) * 0.4
	Ray.x2, Ray.y2 = math.cos(pos * (math.pi/2)) * 1000, math.sin(pos * (math.pi/2)) * 1000
 
	-- Cast the ray and populate the hitList table.
	World:rayCast(Ray.x1, Ray.y1, Ray.x2, Ray.y2, worldRayCastCallback)
end
 
function love.draw()
	-- Drawing the terrain.
	love.graphics.setColor(255, 255, 255)
	for i, v in ipairs(Terrain.Stuff) do
		if v.Shape:getType() == "polygon" then
			love.graphics.polygon("line", Terrain.Body:getWorldPoints( v.Shape:getPoints() ))
		elseif v.Shape:getType() == "edge" then
			love.graphics.line(Terrain.Body:getWorldPoints( v.Shape:getPoints() ))
		else
			local x, y = Terrain.Body:getWorldPoints(v.x, v.y)
			love.graphics.circle("line", x, y, v.Shape:getRadius())
		end
	end
 
	-- Drawing the ray.
	love.graphics.setLineWidth(3)
	love.graphics.setColor(255, 255, 255, 100)
	love.graphics.line(Ray.x1, Ray.y1, Ray.x2, Ray.y2)
	love.graphics.setLineWidth(1)
 
	-- Drawing the intersection points and normal vectors if there were any.
	for i, hit in ipairs(Ray.hitList) do
		love.graphics.setColor(255, 0, 0)
		love.graphics.print(i, hit.x, hit.y) -- Prints the hit order besides the point.
		love.graphics.circle("line", hit.x, hit.y, 3)
		love.graphics.setColor(0, 255, 0)
		love.graphics.line(hit.x, hit.y, hit.x + hit.xn * 25, hit.y + hit.yn * 25)
	end
end
Screenshot of the example.

See Also


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