How to do a turret machine gun?

yaxxar · October 2015

Hello folks, I m on the start of my new game, is based on a tower defense game with a twist of shooter game, my idea is the player can rotate a turret and the turret fires like a machine gun, I read some code from another languages but I m running out of ideas how to make that on Gideros, I know I need to do with an array, but the creation and update of the bullets is a hard thing for me at the moment, do someone have an example? please :o3 thanks!

pie · October 2015

I would use a Timer or enterframe event to know when it's time to fire again:
you need a place (the bullets array) to store references to the bullets on screen, so that you can interact again with each bullet (for example just to get them back into a pool, or to make them moving, depending on your code) then:

 
bullets = {}
counter = 1 --this is to give a unique id to the newly created bullet
 
local function createBullet()
 bx,by=turret:getPosition() --this is to get the turret position as a start x,y for the bullet
 
 bullets[counter] = bullet.new(turret.direction) --create a new bullet instance (or draw it out from pool) named as a number (counter), I assume that you have a property in the  turret to know the direction it is pointing to
 
 stage:addChild(bullets[counter]) --if you're adding the bullets to stage
 bullets[counter]:setPosition(bx,by) 
 
 counter = counter+1 --increase the counter for the next bullet
end

This is a mod version of another example, I didn't test it but should give you something to start from

yaxxar · October 2015

thanks @pie I gonna check this out!

Tom2012 · October 2015

Hi @yaxxar

I've got a turret in my game. I have a turret class and a bullet class.

I'd better attach the files as the code is a bit long to post here...

My turret might have stuff you don't need but I'm sure you'll see how it works. (I'm really basic at programming!) It rotates, sleeps a bit, then starts up again. But the bullets being fired out will be the same for any kind of turret game. (Trig etc...)

It's in level 7 of my game if you want to see it in action. Although you'll have to play the 6 stages before to see it lol sorry

Good luck and ask if there's anything I can do to help!

yaxxar · October 2015

@Tom2012 thanks buddy I gonna see the code

yaxxar · October 2015

I just try a lot of things, but I can t accomplish the logic to fire my turret, on this case I use a monster sprite as turret,

I let my project for checking out

pie · October 2015

just had time for a quick look, I noticed 2 things but couldn't test right now

1) you need to put a limit in enterframe, otherwise in 1 second you shoot 60 bullets

you can use frameCount or a counter you set up.

2) when you create the bullet, I think it's better if you give it a name already, you risk that bulletIndex is updated before createBullet could get it.

local function onEnterFrame(event)
	chuhulu:set("rotation",grados)
	--fireBullet()
	if event.frameCount%application:getFps()==0 then --every second do:
		event:stopPropagation()
 
			if (recoilIndex == 10) then
				if (bulletIndex <= maxBullets) then
					createBullet(bulletIndex)
end
end
end
end
...

Tom2012 · October 2015

@yaxxar I'll have a check of your file as soon as I get home from work.

Tom2012 · October 2015

Hi @yaxxar

I had a look at your project file and played around with the code. I've attached the edited version to this post.

I think what you're trying to do is create a 'pool' of bullets, which are used over and over to avoid creating and removing lots of bullets?

If I were you, I'd just let your game create the bullets and remove them when they leave the 'edge' of the screen, or hit a target etc.

if (self.x < -10 or self.x > 510 or self.y < -10) then
		self:removeEventListener(Event.ENTER_FRAME, self.onEnterFrame, self)	
		stage:removeChild(self)
		print("killed")
	end

It's simpler and you should not have any memory leaks. I've also added the memory checker to your project (which can be removed or disabled in main.lua) which shows the bullets are added and removed from memory.

Hope this helps and good luck!

yaxxar · October 2015

@pie and @Tom2012 thanks a lot for the help I will test all the codes after work, you are awesome guys! thanks \m/ :-bd

yaxxar · October 2015

@pie and @Tom2012 sorry for the delayed answer I tested and now my turret works very good just what I need to start my game! Thanks a lot guys!

Tom2012 · October 2015

Very cool! Look forward to seeing the game progress.

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