Wrap moving object to opposite side of screen.

Physics
#1

Hi,

I know there’s been (much) mention around these parts that you shouldn’t directly adjust a dynamic objects x & y coordinates as it can mess up the physics engine.

So if I have an object that is moved using applyForce how do I get it to wrap around the screen?

#2

In some cases you can’t avoid it.  Screen wrapping is one of those cases.

actions.gif
 
SSKhas code for this: https://roaminggamer.github.io/RGDocs/pages/SSK2/libraries/actions2/#scene-wrapping-scene
 
It is documented, but you can also see how it is used here:
 

  1. Download validation suite: https://github.com/roaminggamer/SSK2/raw/master/validation.zip

  2. Run example: ‘Actions Screen Wrapping Rectangle’

  3. See the code in file:  validation/tests/actions/007_rect_wrapping.lua
     
    This is the CORE of the code

    local actions = ssk.actions – Create a ‘wrapRect’ as a proxy for wrapping calculations – local wrapRect = newRect( group, centerX, centerY, { w = fullh - 100, h = fullh - 100, fill = {0,1,1,0.1}, stroke = {1,1,0,0.5}, strokeWidth = 2 } ) local player = newImageRect( group, centerX, centerY, “images/up.png”, { size = 40 }, { radius = 20 } ) player.enterFrame = function( self ) actions.scene.rectWrap( self, wrapRect ) end; listen( “enterFrame”, player )

#3

The code itself is very short so you can just extract it and modify it as needed:

scene.rectWrap = function( objectToWrap, wrapRectangle ) local right = wrapRectangle.x + wrapRectangle.contentWidth / 2 local left = wrapRectangle.x - wrapRectangle.contentWidth / 2 local top = wrapRectangle.y - wrapRectangle.contentHeight / 2 local bot = wrapRectangle.y + wrapRectangle.contentHeight / 2 if(objectToWrap.x \>= right) then objectToWrap.x = left + objectToWrap.x - right elseif(objectToWrap.x \<= left) then objectToWrap.x = right + objectToWrap.x - left end if(objectToWrap.y \>= bot) then objectToWrap.y = top + objectToWrap.y - bot elseif(objectToWrap.y \<= top) then objectToWrap.y = bot + objectToWrap.y - top end end
#4

Which is what I thought.  I’ve done it no end of times without any problems at all but last night I was having some really weird issues.

Anyway, after a lot of hair pulling and maybe just a little bit of swearing and vowing to throw the computer out of the window I went out for a walk.

When I got back I looked at it with fresh eyes and realised that the issue was due to another (invisible) physics object that is welded to the players ship but I hadn’t set it to isSensor=true.  Once I did that it was problem solved.  It also had the added benefit of solving a couple of other issues that I had been putting off looking into as they weren’t so important.

Happy days.

#5

In some cases you can’t avoid it.  Screen wrapping is one of those cases.

actions.gif
 
SSKhas code for this: https://roaminggamer.github.io/RGDocs/pages/SSK2/libraries/actions2/#scene-wrapping-scene
 
It is documented, but you can also see how it is used here:
 

  1. Download validation suite: https://github.com/roaminggamer/SSK2/raw/master/validation.zip

  2. Run example: ‘Actions Screen Wrapping Rectangle’

  3. See the code in file:  validation/tests/actions/007_rect_wrapping.lua
     
    This is the CORE of the code

    local actions = ssk.actions – Create a ‘wrapRect’ as a proxy for wrapping calculations – local wrapRect = newRect( group, centerX, centerY, { w = fullh - 100, h = fullh - 100, fill = {0,1,1,0.1}, stroke = {1,1,0,0.5}, strokeWidth = 2 } ) local player = newImageRect( group, centerX, centerY, “images/up.png”, { size = 40 }, { radius = 20 } ) player.enterFrame = function( self ) actions.scene.rectWrap( self, wrapRect ) end; listen( “enterFrame”, player )

#6

The code itself is very short so you can just extract it and modify it as needed:

scene.rectWrap = function( objectToWrap, wrapRectangle ) local right = wrapRectangle.x + wrapRectangle.contentWidth / 2 local left = wrapRectangle.x - wrapRectangle.contentWidth / 2 local top = wrapRectangle.y - wrapRectangle.contentHeight / 2 local bot = wrapRectangle.y + wrapRectangle.contentHeight / 2 if(objectToWrap.x \>= right) then objectToWrap.x = left + objectToWrap.x - right elseif(objectToWrap.x \<= left) then objectToWrap.x = right + objectToWrap.x - left end if(objectToWrap.y \>= bot) then objectToWrap.y = top + objectToWrap.y - bot elseif(objectToWrap.y \<= top) then objectToWrap.y = bot + objectToWrap.y - top end end
#7

Which is what I thought.  I’ve done it no end of times without any problems at all but last night I was having some really weird issues.

Anyway, after a lot of hair pulling and maybe just a little bit of swearing and vowing to throw the computer out of the window I went out for a walk.

When I got back I looked at it with fresh eyes and realised that the issue was due to another (invisible) physics object that is welded to the players ship but I hadn’t set it to isSensor=true.  Once I did that it was problem solved.  It also had the added benefit of solving a couple of other issues that I had been putting off looking into as they weren’t so important.

Happy days.