Quick questions about Gideros&Lua

Apollo14 · November 2017

Hi guys!

I'm in the process of learning Gideros&Lua...
I thought it would be better to create one topic for quick newbie questions instead of many.

#1 How to create starry sky?
I've tried this code but I'm getting error "main.lua:24: attempt to index global 'star' (a nil value)"

application:setBackgroundColor(0x02020f)
 
--creating one more star every 1000ms
function createStar()
	star = Shape.new()
	star:setFillStyle(Shape.SOLID, 0xF0F1F2, 1)
	star:beginPath()
	star:moveTo(0,0)
	star:lineTo(1, 0)
	star:lineTo(1, 1)
	star:lineTo(0, 1)
	star:lineTo(0, 0)
	star:endPath()
	star:setPosition(math.random(20,300), 30)
	stage:addChild(star)
end
 
starsTimer = Timer.new(1000, 0)
starsTimer:addEventListener(Event.TIMER,createStar)
starsTimer:start()
 
--moving all stars down
function everyTick()
	star:setY(star:getY()+1)
end
 
stage:addEventListener(Event.ENTER_FRAME,everyTick)

Thanks!

Ninjadoodle · November 2017

@Apollo14 - instead of using a function for the star, I would create a class. Then every time you create an instance, you can move them individually inside the class it self.

The way you’re doing it - I think it might be looking for a star before it’s even created.

jdbc · November 2017

--moving all stars down
function everyTick()
        if (star~=nil) then
	    star:setY(star:getY()+1)
        end
end

You have not created star the first time your ENTERFRAME listener is executed.

Apollo14 · November 2017

if (star~=nil) helps, thx!
but stars stop moving when other stars spawn, how to make them continue going down?
I didn't learn about Lua classes yet))

jdbc · November 2017

if (star~=nil) helps, thx!
but stars stop moving when other stars spawn, how to make them continue going down?
I didn't learn about Lua classes yet))

You have to create a local stars array:
https://www.lua.org/pil/19.2.html

stars = {}
function createStar()
	local star = Shape.new()
	star:setFillStyle(Shape.SOLID, 0xF0F1F2, 1)
	star:beginPath()
	star:moveTo(0,0)
	star:lineTo(1, 0)
	star:lineTo(1, 1)
	star:lineTo(0, 1)
	star:lineTo(0, 0)
	star:endPath()
	star:setPosition(math.random(20,300), 30)
	stage:addChild(star)
        table.add(stars, star)
end
 
--moving all stars down
function everyTick()
        for key,value in pairs(stars) do
	    value:setY(value:getY()+1)
        end
end

Anyway you have to learn more about Lua language first.
http://lua-users.org/wiki/ForTutorial

SinisterSoft · November 2017

@Apollo14 : I think there should me a moving star field particles demo in the examples folder. Particles will be much more efficient.

Ninjadoodle · November 2017

Dude, if you create a class for the class like I suggested then they will all move, as you will be controlling them individually inside the class .

I’ll post you an example shortly

antix · November 2017

@Ninjadoodle, sorry dude bet you to it, bit please do post your implementation too. Everybody can learn from everything :bz

@Apollo14, making a large array of one pixel shapes wouldn't be the most efficient use of resources. The suggestion of @SinisterSoft to use particles is most likely the best solution. If you really needed separate objects then the Pixel class would be a better option as they would perform faster than Shapes.

As an exercise I made a small class that creates that moves (in parallax) a multi layered star field made from Pixels. Each layer has more stars than the previous layer and also moves slower than the previous layer also. Maybe you can find a use for it or maybe you will use particles instead

StarField = Core.class(Sprite)
 
--[[
numLayers - how many layers there will be
numStars - the number of stars in the topmost layer
direction - the direction (0 - 360 degrees) that the layers will move in
speed - the speed the stars will move at
color - the RGB color of the stars
--]]
 
function StarField:init(numLayers, numStars, direction, speed, color)
  local floor, random = math.floor, math.random
 
  self.speed = speed
  self.direction = direction
 
  local width = application:getContentWidth() -- determine screen bounds
  local height = application:getContentHeight()
  self.width, self.height = width, height
 
  -- create layers of stars
  local layers = {}
  for i = 1, numLayers do -- how many layers we will create
    local layer = {} -- new blank layer
    for j = 1, numStars do -- number of stars to create in current layer
      local pixel = Pixel.new(color, 1, 1, 1) -- a star is born
      pixel:setPosition(random(0, width), random(0, height)) -- set random position
      layer[#layer + 1] = pixel -- add star to new layer
    end
    layers[#layers + 1] =layer -- save layer
    color = color * 0.5 -- layers further away are half as bright as the previous layer
    numStars = floor(numStars * 1.75) -- layers further away have more stars than previous layers
  end
  self.layers = layers
 
  -- add stars in reverse order (darkest to lightest)
  for i = #layers, 1, -1 do
    local layer = layers[i]
    for j = 1, #layer do
      self:addChild(layer[j])
    end
  end
 
  self:setDirection(direction)
end
 
-- set new direction for star movement
function StarField:setDirection(direction)
  local sin, cos = math.sin, math.cos
  local speed = self.speed
  local velocity = { -- create new velocity vector from direction and speed
    x = speed * cos(^<(direction)),
    y = speed * sin(^<(direction)),
  }
  self.velocity = velocity
  self.direction = direction
end
 
-- get the direction the stars are currently moving in
function StarField:getDirection()
  return self.direction
end
 
-- set new speed for star movement
function StarField:setSpeed(speed)
  local sin, cos = math.sin, math.cos
  local direction = self.direction
  local velocity = { -- create new velocity vector from direction and speed
    x = speed * cos(^<(direction)),
    y = speed * sin(^<(direction)),
  }
  self.velocity = velocity
  self.speed = speed
end
 
-- get the speed the stars are currently moving at
function StarField:getSpeed()
  return self.speed
end
 
-- call every frame to move stars
function StarField:update(dt)
  local width, height = self.width, self.height -- screen bounds
 
  local velocity = self.velocity
  local vx, vy = velocity.x * dt, velocity.y * dt -- determine actual speed of movement
 
  local layers = self.layers
  for i = 1, #layers do
    local layer = layers[i] -- next layer to process
    for j = 1, #layer do
      local pixel = layer[j] -- next star to move
 
      local x = pixel:getX() + vx -- update x position
      if x < 0 then
        x += width -- if went off left then reset at right
      elseif x > width then
        x -= width -- if went off right then reset at left
      end
 
      local y = pixel:getY() + vy -- update y position
      if y < 0 then
        y += height -- if went off bottom then reset at top
      elseif y > height then
        y -= height -- if went of top then reset bottom
      end
 
      pixel:setPosition(x, y) -- set the stars new position
    end
 
    vx = vx * 0.5 -- each layer moves at half the speed of the previous layer
    vy = vy * 0.5
  end
end

Example of use

application:setFps(60)
application:setBackgroundColor(0x000000)
 
math.randomseed(os.time())
for i = 1, 4 do -- get rid of any pattern at the start
  math.random()
end
 
local stars = StarField.new(3, 60, 45, 57, 0xe0e0e0) -- numLayers, numStars, direction, speed, color
stage:addChild(stars)
 
local function onEnterFrame(e)
  local dt = e.deltaTime
 
  stars:update(dt) -- move all stars in all layers
 
end
 
stage:addEventListener(Event.ENTER_FRAME, onEnterFrame)

jdbc · November 2017

Use particles demo better, it depends what you want do develop.

I always use one main.lua to initiates all scenes in SceneManager when the game starts and then Core.class(Sprite) to create classes for everything as you can see in my complete example game:

https://github.com/jdbcdev/Dots

Practice with Gideros examples and read some lua tutorial to understand syntax before to start creating a game.

Apollo14 · November 2017

Admob changed policy:
https://support.google.com/admob/answer/7562314?ctx=email

Starting January 23, 2018, we will no longer support Google Mobile Ads (GMA) SDK versions lower than 7.0.0 for Android or iOS. To continue serving mobile ads from AdMob, Ad Exchange, or DFP after this date, please upgrade to the latest Google Mobile Ads SDK:

What SDK versions does Gideros use?

oleg · November 2017

What SDK versions does Gideros use?

SinisterSoft · November 2017

You can leave those sections blank and it will use the best version found on the computer.

Apollo14 · November 2017

I'm going through "Gideros Mobile Game Development" ebook https://www.packtpub.com/mapt/book/game_development/9781849696708

It freaks me out, I don't understand a damn f-ing thing in chapter 2.2 "Creating Scenes", either it is extremely newbie-unfriendly, or something is wrong with me personally.

I'm gonna check what's in "step-by-step tutorials" on forum, if there is something that is possible for me to understand from the start. If there is no such stuff, I don't know what to do. Chapter 2.2 raped my brains and it hurts.

SinisterSoft · November 2017

The book was written by a Gideros main dev and forum user: @ar2rsawseen

Maybe he can help address what you don't understand?

antix · November 2017

@Apollo14 Yeah I found some things in there a bit confusing, like you

Have you come across this?? http://appcodingeasy.com/Gideros-Mobile/Manage-Scenes-in-Gideros-Mobile

I think you would learn more from downloading SceneManager from its GitHub page and looking at the example which shows pretty clearly how scenes work. https://github.com/gideros/Scene-Manager

Let us know if you're still having brain freeze :bz

Ninjadoodle · November 2017

Hi @Apollo14

Scenes is Gideros are actually REALLY easy (it just take a little while to understand).

Remember to include the scenemanager.lua file, then do something like this ...

in your main.lua

sceneManager = SceneManager.new({
 
	["menu"] = Menu,
	["stage01"] = Stage01,
	["stage02"] = Stage02,
	["stage03"] = Stage03
 
})
stage:addChild(sceneManager)
sceneManager:changeScene("menu")

in your menu file ...

 
Menu = gideros.class(Sprite)
 
function Menu:init()
 
	-- ADD BUTTON TO GO TO LEVELS ETC.
 
        -- FIRST CREATE YOUR BUTTON THEN DO SOMETHING LIKE THIS ...
       local onTouch = function(target, event)
 
                if target:hitTestPoint(event.touch.x, event.touch.y) then
                        sceneManager:changeScene("stage01", 1, SceneManager.fade)			
                end
        end
 
        stage01Button:addEventListener(Event.TOUCHES_BEGIN, onTouch, stage01Button)
end

in your level/stage files ...

Stage01 = gideros.class(Sprite)
 
function Stage01:init()
 
	-- DO LEVEL STUFF
 
end

keszegh · November 2017

there are in/out events when changing scene, it's natural to listen to them and stop/start the enterframe event of the current stage on them, e.g.:

Stage01 = gideros.class(Sprite)
 
function Stage01:init()
-- INIT STUFF
 self:addEventListener("enterEnd", self.onTransitionInEnd, self)
 self:addEventListener("exitBegin", self.onTransitionOutBegin, self)
end
 
function Stage01:onEnterFrame()
--DO STUFF REPEATEDLY
end
 
function Stage01:onTransitionInEnd()
  self:addEventListener(Event.ENTER_FRAME, self.onEnterFrame,self)
end
 
function Stage01:onTransitionOutBegin()
  self:removeEventListener(Event.ENTER_FRAME, self.onEnterFrame,self)
end

SinisterSoft · November 2017

I add the enter frame event when the scene is initialised - that way any animation I do in the enter frame is there whilst it's being brought in.

keszegh · November 2017

@SinisterSoft is right, probably looks better to add enterframe on enterEnd, however adding touch etc. eventlisteners is safer to do on enterBegin.

Apollo14 · November 2017

Thanks, guys!! I was (and still am) confused with events & event listeners. I need to be patient and keep on learning piece by piece.

Ninjadoodle · November 2017

Hi @Apollo14

Once you understand it, it will become second nature ... Gideros is the easiest/most straight forward tool to code in, that I've encountered (that includes visual tools like Construct 2).

An Event Listener is just a piece of code you attach to a sprite/object, that waits for something to happen.

For example a TOUCH EVENT LISTENER will wait for you to touch the sprite you've attached it to, then run the function you've attached to the listener (for example - play a sound effect and goto Scene 2).

Apollo14 · December 2017

Hi guys!
I've tried to implement vibration real quick with "application:vibrate()"
It vibrates too long. Is it possible to make it shorter? Like short standard Android vibe when we navigate apps.
I didn't find any documentation on this essential feature.

If vibration settings currently are not supported in Gideros, maybe it would be better to make this default vibration short? It will be very handy, because that long vibration rarely is suitable.
Thanks!

SinisterSoft · December 2017

I think it should be application:vibrate([ms]) -- time in ms

SinisterSoft · December 2017

ios doesn't seem to pass it along though...

void vibrate(int ms)
{
#if TARGET_OS_OSX
#else
	AudioServicesPlaySystemSound(kSystemSoundID_Vibrate);
#endif
}

But Android does...

void vibrate(int ms)
{
	JNIEnv *env = g_getJNIEnv();
 
	jclass localRefCls = env->FindClass("com/giderosmobile/android/player/GiderosApplication");
	jmethodID vibrateID = env->GetStaticMethodID(localRefCls, "vibrate", "(I)V");
	env->CallStaticVoidMethod(localRefCls, vibrateID, (jint)ms);
	env->DeleteLocalRef(localRefCls);
}

SinisterSoft · December 2017

It seems Apple reject if you use vibrate for anything other than their standard time...
https://stackoverflow.com/questions/10570553/how-to-set-iphone-vibrate-length

Only in iOS 10+ is it allowed - using this api...
https://www.hackingwithswift.com/example-code/uikit/how-to-generate-haptic-feedback-with-uifeedbackgenerator

SinisterSoft · December 2017

controller:vibrate(ms) also works for some controllers.

Apollo14 · December 2017

"application:vibrate(50)" is what I wanted! Thanks!! :x

SinisterSoft · December 2017

Don't forget this won't apply to iOS, just Android.

Apollo14 · December 2017

Are there any tutorials or documentation on Particles?
I checked basic example StarField.gproj, I don't understand how to make starry sky with particles. Can somebody pls make a quick example?

w=application:getContentWidth()
h=application:getContentHeight()
application:setBackgroundColor(0)
 
stars=Particles.new()
stars:setPosition(w/2,h/2)
stage:addChild(stars)
 
function gameLoop(e)
	stars:addParticles({{x=0,y=0,size=5,ttl=200,speedX=math.random()-0.5,speedY=math.random()-0.5,decay=1.04}})
end
 
stage:addEventListener(Event.ENTER_FRAME,gameLoop)

oleg · December 2017

@Apollo14 http://docs.giderosmobile.com/reference/gideros/Particles/addParticles#Particles:addParticles

antix · December 2017

@Apollo14 are you trying to display a static star field? Or a moving one? Is it supposed to be 2d? or fake 3d?

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