Move camera example Help

zakkwylde · February 2014

Hi,

I am trying to adapt the Box2d camera demo to make the ball follow the mouse when the button is down, but the ball movement is not very good (work ok when the screen is not moving, once the screen scrolls it awful). I am using a mousejoint.

Could an expert assist with a modified version that allows me to use the mouse\touch to drag the ball across the screen and remain smooth? Please?

ar2rsawseen · February 2014

@zakkwylde that seems interesting questions
can not answer right now, will experiment more.
But yes mouse movement will interfere with object centering, so you can't make object centered, but need some other approach to keep it on screen

SimplesApps · March 2014

@ar2rsawseen I'm trying also to achieve @zakkwylde asked.
It's important for me to obtain the right movement.

Would you give us a ray of light on the approach you are thinking or the solution itself?

Thanks.

HubertRonald · March 2014

Hi @zakkwylde and @SimplesApps
I don't know if I understood well your problem.
I believe, you can try with @Niicodemus 's Camera (http://giderosmobile.com/forum/discussion/comment/30138#Comment_30138) and @ar2rsawseen 's Box2dEasy (again sawseen) as follows:

 
----------------
-- in Box2dEasy
----------------
function b2.World:makeDraggable(object)
		--create empty box2d body for joint
		--since mouse cursor is not a body
		--we need dummy body to create joint
		local ground = self:createBody({})
 
		--joint with dummy body
		local mouseJoint = nil
		-- create a mouse joint on mouse down
		object.onDragStart = function(self, event)
 
			if object:hitTestPoint(event.touch.x, event.touch.y) then
				-----------------------------------------------
				object:dispatchEvent(Event.new("pauseCamera"))
				-----------------------------------------------
				object.x0 = event.touch.x
				object.y0 = event.touch.y
				local jointDef = b2.createMouseJointDef(ground, object.body, 
				event.touch.x, event.touch.y, 100000000,1,0)
				mouseJoint = self:createJoint(jointDef)
 
			end
		end
 
		-- update the target of mouse joint on mouse move
		object.onDragMove = function(self, event)
			if mouseJoint ~= nil then
				dx = event.touch.x - object.x0
				dy = event.touch.y - object.y0
				object.body:set("x",object.body:get("x")+dx)
				object.body:set("y",object.body:get("y")+dy)
				mouseJoint:setTarget(event.touch.x, event.touch.y)
				object.x0 = event.touch.x
				object.y0 = event.touch.y
			end
		end
 
 
		-- destroy the mouse joint on mouse up
		object.onDragEnd = function(self, event)
			if mouseJoint ~= nil then
				-----------------------------------------------
				object:dispatchEvent(Event.new("startCamera"))
				-----------------------------------------------
				self:destroyJoint(mouseJoint)
				mouseJoint = nil
			end
		end
 
		-- register for mouse events
		object:addEventListener(Event.TOUCHES_BEGIN, object.onDragStart, self)
		object:addEventListener(Event.TOUCHES_MOVE, object.onDragMove, self)
		object:addEventListener(Event.TOUCHES_END, object.onDragEnd, self)
		return self
	end

and in your main.lua file

 
----------------
-- main
----------------
camera = Camera.new(...)
local world = b2.World.new(...)
local  ball = Bitmap.new(...)	
world:createRectangle(ball, {type = ...})
 
camera:addChild(world:getDebug()) -- if you need this
camera:addEventListener(Event.ENTER_FRAME, function() world:update() end)
 
ball:addEventListener("pauseCamera",
	function()
		print("pause Camera")
		camera:pause()
	end)
 
ball:addEventListener("startCamera",
	function()
		print("start Camera")
		camera:start()
	end)
camera:addChild(camera)
stage:addChild(camera)
 
--p.s. you'll need add background for camera works fine

This was an idea but feel free to improve this code and showing your progress here.

SimplesApps · March 2014

I've tried to adapt the code in order to achieve the correct ball movement with the camera but it's not working.

Hey @ar2rsawseen I noticed you added a change to Box2dEasy (https://github.com/ar2rsawseen/GiderosCodingEasy) after @HubertRonald post his code here.

Have you tried it?

ar2rsawseen · March 2014

@SimplesApps sorry, but no, it was other @HubertRonald code addition

Well the main problem is, that when camera is moving, it moves so the object is centered.
But then, in the same time, you want to take and drag that object.
When dragging it you expect it to move relative to the current screen, but the screen is again, following the object, due to the camera move.

For now I can see only one solution, start camera movement only when you reach the end of the screen while dragging an object.

But if this solution will be helpful or not, I would like to understand more of a purpose of what you are trying to achieve (and I currently can't imagine efficient solution)

HubertRonald · March 2014

Hi @SimplesApps
Yesterday I can't upload sample because internet was failing

(

P.S.
1.- This file not include last version of Box2dEasy
2.- How said @ar2rsawseen: I currently can't imagine efficient solution too
3.- I don't know why I can't upload zip file :P

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