Change Body Properties

HubertRonald · March 2014

Hi folks,

While I was improving my application code, I found this link
http://giderosmobile.com/forum/discussion/2328/change-fixedrotation-runtime/p1

@hgvyas123 said: "it's possible to change the body type".
Then I decided to add this function to @ar2rsawseen 's Box2dEasy

function b2.World:changeBodyState(object, config)
	-- remove this condition if you want change terrain body too
	-- if object.body._conf.shape == "circle" or object.body._conf.shape=="rectangle" then
		local conf = {
				type = "static",
				draggable = false,
				}
 
		if config then
			--copying configuration
			for key,value in pairs(config) do
				conf[key]= value
			end
		end
 
		local setType = b2.STATIC_BODY
		if conf.type == "dynamic" then
			setType = b2.DYNAMIC_BODY
		elseif conf.type == "kinematic" then
			setType = b2.KINEMATIC_BODY
		end	
 
 
		--[[
                    --------------------------
                      Update Script Oct-14-2014
                    --------------------------
                    Prevent bug when you change "conf.draggable" many times to "true"
                    for more information see:
                    <a href="http://giderosmobile.com/forum/discussion/4668/change-body-properties#Item_2" rel="nofollow">http://giderosmobile.com/forum/discussion/4668/change-body-properties#Item_2</a>
 
                ]]
                -- update body type
		self.sprites[object.id].body:setType(setType)
		object.body._conf.type = conf.type
 
		-- update draggable
		-- bug when both object.body._conf.draggable and
		-- conf.draggable are true
		if object.body._conf.draggable ~= conf.draggable then	
			object.body._conf.draggable = conf.draggable
 
			if conf.draggable then
				self:makeDraggable(object)
			else
				if object.onDragStart then
					self:undoDraggable(object)
				end
			end
		end
	--else
		-- Do you want terrain dynamic or kinematic or draggable?
		--print(object.body._conf.shape)
	--end
 
end

I hope this little code can help on something and I hope that @ar2rsawseen can include this in his official version of Box2dEasy for help new users of Gideros.

All suggestions are welcome

ar2rsawseen · March 2014

Wow, great @HubertRonald , will certainly add it

HubertRonald · October 2014

Hi @ar2rsawseen after time!

I found bug in previous script

For example:

 
require "Box2dEasy"
 
local sun = Bitmap.new(Texture.new("sun_shades.png", true))
sun:setAnchorPoint(0.5, 0.5)
sun:setPosition(150, 150)
stage:addChild(sun)
 
local world = b2.World.new(0, 0, true)
world:createCircle(sun, {type = "dynamic"})
 
---------------------
-- here's the bug!!!
---------------------
local n=5 --n>=2 
for i=1,n do
 world:changeBodyState(sun,{type = "static", draggable = true}) -- or type="kinematic" or type="dynamic"
end
world:changeBodyState(sun,{draggable = false})
world:changeBodyState(sun,{draggable = true})

So the sprite "sun" works like Elastic Joints of Gideros' Example Projects, It happens because previous script erases the last joint and no previous (n>=2 on "for" loop) joints that were created. Then I only had to consider the "draggable config" is different for setup:

 
--[[
      --------------------------
       Update Script Oct-14-2014
      --------------------------
 ]]
 
       --......
 
            if object.body._conf.draggable ~= conf.draggable then
 
       --.......

The original Script is already fixed with the comment made earlier

Cheers

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