Box2D Gamplay problem

GhostLeader · March 2014

Hi i have new problem in my gameplay character i figure out how to do a jump movement but i still have a problem with circle shape, every frame is saving the last position and creating a pink circle shape can someone help me plz ?

for the frame function:

-- Function to enter frame
function level:onEnterFrame()
	-- edit the step values if required. These are good defaults!
	self.world:step(1/60, 8, 3)
	--iterate through all child sprites
	for i = 1, self:getNumChildren() do
		--get specific sprite
		local sprite = self:getChildAt(i)
		-- check if sprite HAS a body (ie, physical object reference we added)
		if sprite.body then
			--update position to match box2d world object's position
			--get physical body reference
		local body = sprite.body
		-- update object's position to match box2d world object's position
		-- apply coordinates to sprite
		body.object:setPosition(body:getPosition())
		--apply rotation to sprite
		body.object:setRotation(math.deg(body:getAngle()))
		end
	end
end

for my main character :

mainBosso = Core.class(Sprite)
 
function mainBosso:init(level, x, y)
	self.level = level
	self:setPosition(x,y)
 
	--create bitmap object from ball graphic
	self.bitmap = Bitmap.new(self.level.g:getTextureRegion("BossoBleu.png"))
	--reference center of the ball for positioning
	self.bitmap:setAnchorPoint(0.5,0.5)
	self:addChild(self.bitmap)
 
	self:addEventListener(Event.MOUSE_DOWN, self.onMouseDown, self)
	self:addEventListener(Event.MOUSE_UP, self.onMouseUp, self)
end
 
function mainBosso:createBody()
	--get radius
	local radius = (self.bitmap:getWidth()/2)*0.85
 
	--create box2d physical object
	local body = self.level.world:createBody{type = b2.DYNAMIC_BODY}
 
	--copy all state of object
	body:setPosition(self:getPosition())
	body:setAngle(math.rad(self:getRotation()))
	local circle = b2.CircleShape.new(0, 0, radius)
 
	local fixture = body:createFixture{shape = circle, density = 1, 
	friction = 0.1, restitution = 0.8}
 
	body.type = "main"
	self.body = body
	body.object = self
	table.insert(self.level.bodies, body)
end
 
-- Jump Function 
function mainBosso:onMouseDown()
	self.startX = self:getX()
	self.startY = self:getY()
end
 
function mainBosso:onMouseUp()
		self:createBody()
		--applye impulse to target
		self.body:applyLinearImpulse(0, -10, self:getX(), self:getY())
		self:removeEventListener(Event.MOUSE_UP, self.onMouseDown, self)
end

GhostLeader · March 2014

and i know how to scroll a parallax ground but if there's a tutorial with how to scroll the ground with generated object it will be nice

ar2rsawseen · March 2014

@GhostLeader that could be because you call self:createBody() on each mouse up event
meaning every time you release a mouse/finger, it creates a new body

You should create body once inside init and use it

Also about paralaxing, then there are two ways:

1) actually moving box2d object through the world (what most of platformers do)
and could be done something like this:
http://appcodingeasy.com/Gideros-Mobile/Gideros-Camera-Move

2) keeping the body in the same place and moving the world:
http://giderosmobile.com/forum/discussion/comment/27868#Comment_27868

GhostLeader · March 2014

thank you again and how can you hide ChainShape or do i just place them behind my background

ar2rsawseen · March 2014

What do you mean hide? If ChainShape is showing, it means debug draw is on, just search and comment out debugDraw

GhostLeader · March 2014

no it's fine i hide it

hgvyas123 · March 2014

actually disabling debug draw is more good by doing so you can save some extra drawings of physics body putting them behind background will still draw them and put some extra load on performance

ar2rsawseen · March 2014

@hgvyas123 so true
and actually not simple extra load, but a lot of load, debug draw is very very unefficient

GhostLeader · March 2014

actually im having a problem on positioning my background , the ground and my pause button and restart button because of the new camera movement can someone help me ?
and i have a problem with createLayer() function if #self .layers > 2 i got the problem classes/GiderosCodingEasy.lua:125: index '__userdata' cannot be found
stack traceback:
classes/GiderosCodingEasy.lua:125: in function 'removeChild'
Scenes/level.lua:280: in function 'createLayer'
Scenes/level.lua:306: in function

here's my level.lua

ar2rsawseen · March 2014

@GhostLeader to deal with running away pause and restart buttons, etc there are 2 options
1) add them to the stage and remove when scene exits
2) create a separate layer for camera and add all worlds object to that, thus the scene itself does not move

About the second, basically error happens here:
self.layer:removeChild(self.layers[1].layer)

meaning that either the bitmap was not saved or was already removed
you can try changing it to something like this:

if self.layers[1].layer then
    self.layers[1].layer:removeFromParent()
    self.layers[1].layer = nil
end

GhostLeader · March 2014

and how can i use setLinearVelocity with other class object because i have a class for my main character and i want to use createBody() not only self.level.world:createCircle(self.bitmap, {type = "dynamic"})

ar2rsawseen · March 2014

Sorry I don't really get the last one.
Usually what I do is save reference to a body, like

local bmp = Bitmap.new(...)
--then add physical body reference
bmp.body = body
 
-- and when you need to push bmp somewhere, you simply use
bmp.body:setLinearVelocity --etc

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