Creating groups in Gideros

simran · May 2014

I have number of objects that I added to stage, Now, out of them, there are couple of objects that I want to group, so If my player collides with any of them , I can respond to that. So, I believe all those objects are to be grouped?

If I already have added them to stage, do I need to add a line of code to add them to a group and so add group to the stage, or is there any possible alternative ?
Please let me know if there is any preferred way for achieving the same.

Thank you GIderos

ar2rsawseen · May 2014

Hello @simran
grouping example:

local group1 = Sprite.new()
local group2 = Sprite.new()
stage:addChild(group1)
stage:addChild(group2)
 
group1:addChild(Bitmap.new(Texture.new("image1.png")))
group1:addChild(Bitmap.new(Texture.new("image2.png")))
 
group2:addChild(Bitmap.new(Texture.new("imagea.png")))
group2:addChild(Bitmap.new(Texture.new("imageb.png")))

simran · May 2014

@ar2rswseen: Thank you , but how can I get width, height, position of all the objects added in a group since I want to detect their collision with a character?

SinisterSoft · May 2014

You would have to loop through the children of group1 or 2 and check their x,y,w,h against the x,y,w,h of your character, break out of the loop when you find a collision.

simran · May 2014

@SinisterSoft : Oh, Thanks a ton! But, do I access them in usual way, like group1.member1 or just address them using member names only?

ar2rsawseen · May 2014

method to check for collision, put it somewhere in the project, for example in init.lua file:

function Sprite:collidesWith(sprite2)
	local x,y,w,h = self:getBounds(stage)
	local x2,y2,w2,h2 = sprite2:getBounds(stage)
 
	return not ((y+h < y2) or (y > y2+h2) or (x > x2+w2) or (x+w < x2))
end

then use it while looping through group

for i = 1, gourp1:getNumChildren() do
	local sprite = scope:getChildAt(i)
	if sprite:collidesWith(someOtherSprite) then
		--they collide
	end
end

simran · May 2014

Thanks a ton, I am sorry for being a noob, but actually my object that is colliding is
something like this:

self.anim{

bitmap:getTextureRegion("1.png"),
bitmap:getTextureRegion("2.png"),

and so on
}

so, how to pass this object as parameter?, please?
Secondly, this group1(in my code) contains objects that are created inside a class, so using Sprite: CollidesWith(secondsprite), using Sprite as first argument, will it work?

ar2rsawseen · May 2014

@simran so bitmap in your context is actually a TexturePack?

You can only check collisions with Sprite objects and classes which inherit from Sprite, as Bitmap, TextField, etc.

And you can't check collision between whole groups, you need to specifically check for each Sprite, by looping through the groups

simran · May 2014

Oh, but one might be having hundreds of images in a sprite sheet, so what do we do in that case, generally players in games are a set of sprite sheets only and indeed we need to check the player's collisions with any of the objects, what is the approach for that?

ar2rsawseen · May 2014

@simran what do you mean by spritesheet? a texture pack?

But texture pack are set to Bitmaps as texture regions or a MovieClip

You need to check collisions between the renderable objects as Bitmaps and not Texture packs or texture regions

Maybe if you could post more code, it would be easier to understand what you want to achieve

simran · May 2014

Okay,
So, here is the code that I have to render the images from Texture Pack, I meant to refer to images from texture pack only,(sorry for teh confusion)

local pack = TexturePack.new("Charecter.txt", "Charecter.png")

self.anim = {
Bitmap.new(pack:getTextureRegion("f1.PNG")),
Bitmap.new(pack:getTextureRegion("f2.PNG")),
Bitmap.new(pack:getTextureRegion("f3.PNG")),
--Bitmap.new(pack:getTextureRegion("l1.PNG")),
--Bitmap.new(pack:getTextureRegion("l2.PNG")),
--Bitmap.new(pack:getTextureRegion("l3.PNG")),
Bitmap.new(pack:getTextureRegion("b1.PNG")),
Bitmap.new(pack:getTextureRegion("b2.PNG")),
Bitmap.new(pack:getTextureRegion("b3.PNG")),
--Bitmap.new(pack:getTextureRegion("r1.PNG")),
--Bitmap.new(pack:getTextureRegion("r2.PNG")),
--Bitmap.new(pack:getTextureRegion("r3.PNG"))

}

self.frame = 1
self:addChild(self.anim[1])
self:setPosition(220, 50)

and now I have other objects that I have added as images on the stage and want to check if any of them collide with the above mentioned Character , so my question is how do I check if self.anim mentioned above is colliding with any of the other objects?

P.S -> The images in the self.anim are just that of a single character which change with time to render motion of the Charecter

ar2rsawseen · May 2014

ah, I see, so that actually relate to a single character. Well I assume you animate it by adding/removing those bitmaps from stage or scene?

That would actually be quite inefficient.

The default way would be to create animations using MoveClip:
http://docs.giderosmobile.com/reference/gideros/MovieClip#MovieClip

Which would basically add/remove Bitmaps for you

Alternative ways would be to create single Bitmap obejct and change in textures using setTexture or setTextureRegion

Another alternative would be using TNT Animator Studio: http://www.tntparticlesengine.com/?page_id=31

In all of these cases, there will be single instance (either MovieClip or Bitmap or TNT Animator class) which would represent the main character, and which can be used for collision check using collidesWith method

simran · May 2014

Oh, okay

Thanks a ton ! BUt still I would like to know if it is possible to use collides with using the same texture region technique, Is it?

SinisterSoft · May 2014

@ar2rsawseen

function Sprite:collidesWith(sprite2)
local x,y,w,h = self:getBounds(stage)
local x2,y2,w2,h2 = sprite2:getBounds(stage)

return not ((y+h < y2) or (y > y2+h2) or (x > x2+w2) or (x+w < x2))
end

for i = 1, gourp1:getNumChildren() do
local sprite = scope:getChildAt(i)
if sprite:collidesWith(someOtherSprite) then
--they collide
end
end

With normal Lua, would this be faster than getting the bounds locally to the main routine rather than having a subroutine (function) in this case? Does Lua somehow cache the functions?

Also what would be the case with LuaJIT ?

simran · May 2014

@ar2rsawseen: Yes, I add them to the stage for creating the animation after checking a couple of conditions, but I now so desperately want to know if it is possible to use collideswith with this same programming style, please?

ar2rsawseen · May 2014

@SinisterSoft it would be faster to cache the bounds of the character you are testing on others yes. Definitely in plain Lua.
In LuaJIT there are lots of optimizations underneath, and I think it actually runs your code and generates optimized native code by rearranging command sets, so this kind of stuff should be optimized by LuaJIT automatically.

ar2rsawseen · May 2014

@simran
Are all the character images the same dimensions?
if yes, then all you have to do is to always take the first Bitmap and use it to check the collisions:

self.anim[1]:collidesWith(otherSprite)

If not then, you probably save the current image index in some variable, so you would know which animation to switch to next, right?

Then you can use this variable to access current Bitmap:

self.anim[variable]:collidesWith(otherSprite)

You also mentioned that they are in separate classes, but if they are stored as instance properties as:

dummy = Core.class(Sprite)
 
function dummy:init()
    self.anim = {...}
end

Then you can also access them as instance properties:

local d = dummy.new()
d.anim[variable]:collidesWith(otherSprite)

simran · May 2014

@ar2rsawseen : Thank you ,thank you ,thank you so much .Good day

simran · May 2014

Hey, so it still says, attempt to call colldieswith (a nil value)

Here is teh relative piece of code

cute = dummy.new()
stage: addChild(cute)

for i = 1, groupA:getNumChildren() do
local sprite = groupA:getChildAt(i)
if cute.anim[1]:collidesWith(sprite) then
youLoose()
end

end

function sprite1:collidesWith(sprite2)
local x,y,w,h = sprite1:getBounds(stage)
local x2,y2,w2,h2 = sprite2:getBounds(stage)

return not ((y+h < y2) or (y > y2+h2) or (x > x2+w2) or (x+w < x2))
end

ar2rsawseen · May 2014

@simran you should create init.lua file in your project (init.lua with exactly this name, this file will be special, because it will be the first one to execute)

And in this init.lua file, you need to put exactly this methods:

function Sprite:collidesWith(sprite2)
    local x,y,w,h = self:getBounds(stage)
    local x2,y2,w2,h2 = sprite2:getBounds(stage)
    return not ((y+h < y2) or (y > y2+h2) or (x > x2+w2) or (x+w < x2))
end

It will add collidesWith method to any obejct that is Sprite or Sprite inherited instance

simran · May 2014

@ar2rsawseen: Okay, thanks a ton, I was completely unaware of this init.lua thing that it is always the first one to be called, so I did exactly the same as suggested and it did not give an error, but it still does not detect the collision. I have attached the image, in the image the clock hands are over which we have the loop and the character is self.anim, but it just crosses it and it never detects the collision, what seems wrong here?I am sorry again

ar2rsawseen · May 2014

Really hard to tell what is not working. Are you sure you check for collision for right obejcts and recheck it on every enter frame event?

Can you post more code or maybe share a project sample for review?

simran · May 2014

I got what part of it is not working, I posted it here, please check:
http://giderosmobile.com/forum/discussion/4908/how-to-get-updated-position-of-x-and-y-when-position-is-changing-with-time#Item_1

simran · May 2014

actually, the positions of both are changing at may be less than a second and what we were using in above example, the values were never updated

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