Corona SDK custom physics bodies - lua

Question

i have some trouble with the custom shapes in corona.
Here is my code and what it does is that i'm adding some spheres to the scene so that they fall inside a basket, this basket is the custom shape object that i defined in the newBasket() function, the problem is that the basket does collide with the ground object but it doesn't collide with the spheres and i don't know why, please someone help me here, i can't find a solution elsewhere, thanks in advance.
_W = display.contentWidth
_H = display.contentHeight
--Physics
local physics = require("physics")
physics.start()
physics.setDrawMode("debug")
-- iOS
display.setStatusBar(display.HiddenStatusBar)
-- screen boundaries
local ground = display.newRect(0, _H, _W, 5)
local leftWall = display.newRect(0,0,1,_H)
local rightWall = display.newRect(_W,0,1,_H)
physics.addBody(ground, "static", {friction = .2, bounce = .1})
physics.addBody(leftWall, "static", {friction = .2, bounce = .1})
physics.addBody(rightWall, "static", {friction = .2, bounce = .1})
local function newBasket()
local body = display.newImage("assets/basket.png")
body.x = 0 body.y = 0
local physics_body = {}
physics_body["basket"] = {
{
--LeftArm
density = 10, friction = 10, bounce = 0.15,
shape = {-126, 40, -110, 40, -140, -64, -156, -64}
},
{
--Bottom
density = 10, friction = 1, bounce = 0,
shape = {-121, 60, 125, 60, 128, 40, -126, 40}
},
{
--RightArm
density = 10, friction = 10, bounce = 0.15,
shape = {113, 40, 129, 40, 158, -64, 143, -64}
}
}
physics.addBody(body, unpack(physics_body["basket"]) )
return body
end
local basket = newBasket()
basket.x = _W * .5 basket.y = _H - 100
local function newPlanet()
local planets = {
{img = "bigBall.png", radius = 45},
{img = "mediumBall.png", radius = 30},
{img = "smallBall.png", radius = 20}
}
local n = math.random(1,3)
local img = "assets/" .. planets[n].img
local ball = display.newImage(img)
ball.x = math.random((_W * 0.5) -100, (_W * 0.5) + 100) ball.y = 0
physics.addBody(ball, {bounce = 0.3, radius = planets[n].radius})
end
local function spawnPlanets(number)
local function spawn(e)
newPlanet()
if(e.count == number) then
timer.cancel(tmr)
tmr = nil
end
end
tmr = timer.performWithDelay(500, spawn, number)
end
spawnPlanets(20)

Answer 1

According to the manual:
If a shape is specified, then the body boundaries will follow the polygon provided by the shape. Note that the maximum number of sides per shape is eight, and all angles must be convex. [...] The shape coordinates must be defined in clockwise order, and the resulting shape must be convex-only.
So you have two issues working against you. First the shapes must be defined in clockwise order, as I've done in the below example. Secondly, all shapes must be convex (even complex body shapes) so you can't do anything that turns in on itself like a crescent moon or basket.
Unfortunantly, this means you have to make your basket as 3 separate shapes. Also, since they are now separate shapes, they won't stay stuck together when they fall (unless you use joints). I've just made the basket 3 static bodies and put it in the right place to start with:
local function newBasket()
local physics_body = {}
physics_body["basket"] = {
{
--LeftArm
density = 10, friction = 10, bounce = 0.15,
shape = {-126, 40, -156, -64, -140, -64, -110, 40 }
},
{
--Bottom
density = 10, friction = 1, bounce = 0,
shape = {-121, 60,-126, 40, 128, 40, 125, 60 }
},
{
--RightArm
density = 10, friction = 10, bounce = 0.15,
shape = {113, 40, 143, -64, 158, -64, 129, 40 }
}
}
for k,shape in pairs(physics_body["basket"]) do
local body = display.newRect(0, 0, 200, 100)
body.x = display.contentCenterX
body.y = display.contentHeight - 60
physics.addBody(body, 'static', shape )
end
end
newBasket()