bug report

Comments

• atilim Maintainer

  December 2011

  Hi,
  
  Can you try this small example:

  require "box2d"   local scale = b2.getScale()   local world = b2.World.new(0, 10, true)   local body = world:createBody({type = b2.DYNAMIC_BODY, position = {x = 160, y = 0}}) local shape = b2.CircleShape.new(0, 0, 30) body:createFixture({shape = shape, density = 1})   local function onEnterFrame() world:step(1/60, 8, 3) end   stage:addEventListener(Event.ENTER_FRAME, onEnterFrame)   local function applyLinearImpulse() local x, y = body:getPosition() body:applyLinearImpulse(0, -20, x/scale, y/scale) end   stage:addEventListener(Event.MOUSE_DOWN, applyLinearImpulse)   local debugDraw = b2.DebugDraw.new() world:setDebugDraw(debugDraw) stage:addChild(debugDraw)

  In my tests, it works on PC, iOS and Android.
  
  Note: We realized that applyLinearImpulse and applyForce functions don't consider physics scale. It's a bug and now fixed. To overcome this issue, I get the physics scale and apply it to applyLinearImpulse.

  http://en.wikipedia.org/wiki/Cytorus

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• alexzheng Guru

  December 2011 edited December 2011

  hi,
  I tried your code, and It works on both pc and phone device.
  finally, I got the answer.
  here is the code example reproduce the issue
  the code work well on pc but not on my nexus s.
  
  
  require "box2d"
  
  local scale = b2.getScale()
  
  local world = b2.World.new(0, 10, true)
  
  
  --add ground
  local ground = world:createBody({})
  
  ground.name = "ground"
  
  local shape = b2.EdgeShape.new(0, application:getLogicalHeight(), application:getLogicalWidth(), application:getLogicalHeight())
  ground:createFixture({shape = shape, density = 0})
  
  local body = world:createBody({type = b2.DYNAMIC_BODY, fixedRotation = true, position = {x = 160, y = application:getLogicalHeight()}})
  
  --[[
  local shape = b2.CircleShape.new(0, 0, 30)
  body:createFixture({shape = shape, density = 1})
  
  shape = b2.CircleShape.new(30, 0, 60)
  body:createFixture({shape = shape, density = 1})
  ]]
  
  local shape = b2.PolygonShape.new()
  shape:setAsBox(20, 20, 0, 0, 0)
  body:createFixture{shape = shape, density = 1}
  
  shape = b2.PolygonShape.new()
  shape:setAsBox(20, 10, 0, 20, 0) ------notice here, the fourth param should less than 20, or it will be hold by the ground
  body:createFixture{shape = shape, density = 1}
  
  local function onEnterFrame()
  world:step(1/60, 8, 3)
  end
  
  stage:addEventListener(Event.ENTER_FRAME, onEnterFrame)
  
  local function applyLinearImpulse()
  local x, y = body:getPosition()
  print(scale)
  body:applyLinearImpulse(0, -20, x/scale, y/scale)
  end
  
  stage:addEventListener(Event.MOUSE_DOWN, applyLinearImpulse)
  
  local debugDraw = b2.DebugDraw.new()
  world:setDebugDraw(debugDraw)
  stage:addChild(debugDraw)
  
  
  

  My Games
  https://sites.google.com/site/xraystudiogame

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• atilim Maintainer

  December 2011

  You're right. For this case box2d at desktop and mobile behaves differently. Currently I cannot predict the main reason. It's an interesting case and I'll investigate more.

  http://en.wikipedia.org/wiki/Cytorus

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• alexzheng Guru

  December 2011

  btw,I found setAngle is missed for body.

  My Games
  https://sites.google.com/site/xraystudiogame

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• atilim Maintainer

  December 2011

  Thank you. I've added this function.
  

  http://en.wikipedia.org/wiki/Cytorus

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