Collision Polygon

[childonline]

So I made this little jelly-like square by joining 4 circle shaped bodies with distance joints and it worked out pretty ok.
Problem is, with this type of implementation collision detection occurs only for the corners of the square and not with the edges.

Is there a way to create a bounding polygon having the xy coordinates of the 4 bodies as vertices, such that if another body touches a jelly square edge the pivots react and compress?

Here is the code so far, it started out from the love.physics tutorial (arrow keys to move square around):

Code: Select all

function love.load()
	world = love.physics.newWorld(-650, -650, 650, 650)
	world:setGravity(0,700)
	world:setMeter(64)
  
	bodies = {}
	shapes = {}
	joints = {}
  
	bodies[0] = love.physics.newBody(world, 625/2, 625, 0, 0)
	shapes[0] = love.physics.newRectangleShape(bodies[0], 0, 0, 800, 50, 0)
  
	bodies[1] = love.physics.newBody(world, 100, 100, 10, 0)  
	bodies[2] = love.physics.newBody(world, 200, 100, 10, 0)
	bodies[3] = love.physics.newBody(world, 200, 200, 10, 0)
	bodies[4] = love.physics.newBody(world, 100, 200, 10, 0)
	
	for i = 1,4 do
		shapes[i] = love.physics.newCircleShape(bodies[i], 0, 0, .1)
	end
	
	joints[1] = love.physics.newDistanceJoint(bodies[1], bodies[2],100,100,200,100)
	joints[2] = love.physics.newDistanceJoint(bodies[2], bodies[3],200,100,200,200)
	joints[3] = love.physics.newDistanceJoint(bodies[3], bodies[4],200,200,100,200)
	joints[4] = love.physics.newDistanceJoint(bodies[4], bodies[1],100,200,100,100)
	joints[5] = love.physics.newDistanceJoint(bodies[1], bodies[3],100,100,200,200)
	joints[6] = love.physics.newDistanceJoint(bodies[2], bodies[4],200,100,100,200)
	
	for i = 1,6 do
		joints[i]:setFrequency(4)  
		joints[i]:setDamping(0.75)
	end
	
  	love.graphics.setBackgroundColor(104, 136, 248)
	love.graphics.setMode(650, 650, false, true, 0)
  
end

function love.update(dt)
	world:update(dt)
	for i = 1,4 do
		if love.keyboard.isDown("right") then
			bodies[i]:applyForce(300, 0)
		elseif love.keyboard.isDown("left") then
			bodies[i]:applyForce(-300, 0)
		elseif love.keyboard.isDown("up") then
			bodies[i]:applyForce(0,-300)
		end
	end	
end

function love.draw()
	local x1, y1, x2, y2, x3, y3, x4, y4 = shapes[0]:getBoundingBox()
	local boxwidth = x3 - x2
	local boxheight = y2 - y1
	love.graphics.setColor(72, 160, 14)
	love.graphics.rectangle("fill", bodies[0]:getX() - boxwidth/2, bodies[0]:getY() - boxheight/2, boxwidth, boxheight)
	
	love.graphics.setColor(193, 47, 14)
	love.graphics.polygon('fill', bodies[1]:getX(), bodies[1]:getY(),bodies[2]:getX(), bodies[2]:getY(),bodies[3]:getX(), bodies[3]:getY(),bodies[4]:getX(), bodies[4]:getY())
end

[Taehl]

Instead of four circles for the corners, why not use four rectangles for the edges? Just set them to not collide with each other, and it should work quite well.