New to lua, need help with tables (and now collisions)

[nevon]

First of all, create a function to handle your collision checking. That will make things a lot more readable. For example, this one (you're welcome) checks a rectangle against a circle (which seems like what you want to do):

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function circRectCollision(rectx, recty, rectwidth, rectheight, pointx, pointy, radius)
	local pow = math.pow
	local root = math.sqrt
	--Check if the projectile is inside the enemy bounding box
	if pointx > rectx-radius and pointy > rectyy-radius and pointx < rectx+rectwidth+radius and pointy < recty+rectheight+radius then
		return true
	--Check if the projectile is touching the corner of the rect bounding box
	elseif root( pow( rectx-pointx, 2 ) + pow( recty-pointy, 2 ) ) < radius or
	   root( pow( rectx+rectwidth-pointx, 2 ) + pow(recty-pointy, 2 ) ) < radius or
	   root( pow( rectx-pointx, 2 ) + pow( recty+rectheight-pointy, 2 ) ) < radius or
	   root( pow( rectyx+rectwidth-pointx, 2 ) + pow( recty+rectheight-pointy, 2 ) ) < radius then
		return true
	end
end

Then you would do something like this:

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function love.update(dt)
    local enemyremovetable = {}
    local projectileremovetable = {}

    for i,v in ipairs(enemies) do
        for n,k in ipairs(projectiles) do
            
            if circRectCollision( v.x, v.y, 32, 32, k.x, k.y, 1 ) then
                table.insert(enemyremovetable, i)
                table.insert(projectileremovetable, n)
            end

        end
    end

    for i,v in ipairs(enemyremovetable) do
        table.remove(enemies, v-i+1)
    end

    for i,v in ipairs(projectileremovetable) do
        table.remove(projectiles, v-i+1)
    end
end

[fylth]

You sir are a gentleman of the highest order, with a bit of tweaking that worked a treat! Have some karma

Just going to play around with this a bit more (adding a health variable which is decremented on collision due to the amazingly huge amount of bullets my player spews forth, then get some increasingly hard waves) and then get to work on scoring and a menu, then I will have completed my first (amazingly simple) game! Hooray!

*EDIT*

Hate to keep asking questions, this one's to do with tables again though and I just need to know the correct syntax to deal with it.

I'm trying to get the enemies hp to reduce by 1 per hit, so in the deceleration for the enemy type I have

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enemy1 = {
	image = love.graphics.newImage("enemy1.png"),
	x = 0,
	y = -32,
	hp = 30
	}

And it i've changed the code for entering each enemy in the enemy table to

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		table.insert(enemy, {x = (enemy1.x + randnum), y = enemy1.y, image = enemy1.image, hp = 30})

However, i'm not sure how to now effect this variable now in the collision code, at the moment I have

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enemy(i,v).hp= enemy(i,v).hp - 1

which I know isn't right and I must've tried a hundred variations trying to use examples from earlier in the code but none seem to work...so, a little bit more help? Much appreciated, again sorry for asking for help so often

[kikito]

I would get rid of the initial 'enemy1'. Use variables instead:

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  image = love.graphics.newImage("enemy1.png")
  enemy_y = -32

I also recommend renaming your 'enemy' variable to 'enemies'; this name is more appropiate since the variable holds more than one enemy.

So your enemies can now be created like this:

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table.insert(enemies, {x = randnum, y = enemy_y, image = image, hp = 30})

Which is just a bit simpler.

You nearly got the e syntax right. But remember that if you want to access the attribute x of a table you have to use brackets: table[x], not table(x)

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enemies[i].hp= enemies[i].hp - 1

I also removed the 'v'; I didn't know what it was, but probably it didn't belong there (enemies is a mono-dimensional table, and you can't index it with two variables ).

[zac352]

Aww. I missed out. :d

[fylth]

Well, this appears to be becoming a thread where by I post all progress and problems I'm having with this game, so why not continue haha

I have a...perplexing bug (for me, at least), which is when one enemy leaves the bottom of the screen the next enemy on the screen is removed instead (or as well? not sure what happens to the ones which make it off screen, if they aren't being removed it might explain the slow down later down).

Here's the code for the enemy removal section, see any problems?

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for i,v in ipairs(enemy) do
		v.y = v.y + 0.6
		if v.y > 600 then
			table.insert(removeenemy, i)
			health = health - 5
		end
	end

--big chunk of code for other stuff, I'm not very organised

 for i,v in ipairs(removeenemy) do
       table.remove(enemy, v-i+1)
    end

I'll attach the file itself in case anyone wants to take a look?

(Oh, and if anyone can recommend a way of lessening the slow down when firing that would be appreciated)

[Robin]

Using a remove flag, rather than a remove queue might help:

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for i,v in ipairs(enemy) do
	v.y = v.y + 0.6
	if v.y > 600 then
		v.remove = true
		health = health - 5
	end
end

-- ...

for i = #enemy, 1, -1 do
	if enemy[i].remove then
		table.remove(enemy, i)
	end
end

Hope this helps.