Help with making sprites appear in random places

joshlong93

Hi guys,

I'm attempting to make a little game where you have a character, which is a sprite, and by using the accelerometer you tilt the iPad to collect little stars that appear, which will also be sprites. Once you've touched the star it disappears.

There are 5 different coloured stars that I want to appear in random places, when you collect them you get points and more start appearing.

I think I need to use a table to hold the different stars and have them appear on the screen, but I can't find any really easy to understand tutorials or examples on how to use tables in this way.

Could any of you link me to a really good tutorial, or quickly write up an example table that does this?

Please say if you need any more information, I'd post all my current code but I don't know if it would really be relevant.

Thanks

dave1707

@joshlong93 This help.

EDIT: Code modified from the original.

displayMode(FULLSCREEN)

function setup()
    tab={}
    for z=1,5 do
        table.insert(tab,vec2(math.random(50,WIDTH-50),math.random(50,HEIGHT-50)))
    end
    sp={"Planet Cute:Character Boy",
        "Planet Cute:Character Cat Girl",
        "Planet Cute:Character Horn Girl",
        "Planet Cute:Character Pink Girl",
        "Planet Cute:Character Princess Girl"}
end

function draw()
    background(40,40,50)
    for a,b in pairs(tab) do
        sprite(sp[a],b.x,b.y)
    end
end

dave1707

@joshlong93 See this ling to a game I made. It sounds similar to what you're doing. Maybe it will help.

http://codea.io/talk/discussion/4839/starter-game#Item_9

joshlong93

Thanks @dave1707 , I think I get most of that.
What do the z, a and b stand for? Also, how would I make each of the 5 stars a different sprite?

Thanks, for the quick answer!

dave1707

@joshlong93 The z,a,b are just variables that I use. z is a variable in the "for" loop that goes from 1 to 5. The a and b are variables in another "for" loop. The "a" is a counter that goes from 1 to the number of entries in the table "tab". "b" is the values in the table. Since I created the entries with a vec2, that means there are 2 values per entry. The way to access them is with b.x and b.y . You could put the different sprites in a table and use the "a" variable to access that table. I'll give you an example soon.

dave1707

@joshlong93 I modified the original code to show 5 different sprites.

joshlong93

that's been really helpful thank you @dave1707! If I could just ask one more question, how would I randomly make more than one of a particular star show up?

dave1707

@joshlong93 I'm not sure if this is what you're after. I show 4 sprites and the 5th one will be a duplicate of one of the 4.

displayMode(FULLSCREEN)

function setup()
    tab={}
    for z=1,5 do
        table.insert(tab,vec2(math.random(50,WIDTH-50),math.random(50,HEIGHT-50)))
    end
    sp={"Planet Cute:Character Boy",
        "Planet Cute:Character Cat Girl",
        "Planet Cute:Character Horn Girl",
        "Planet Cute:Character Pink Girl"}
    r=math.random(4)
end

function draw()
    background(40,40,50)
    for a,b in pairs(tab) do
        if a==5 then
            sprite(sp[r],b.x,b.y)
        else
            sprite(sp[a],b.x,b.y)
        end
    end
end

Coder

This code allows for didpfferent types of stars with different colors, values and sizes etc.

-- Game
displayMode(OVERLAY)
supportedOrientations(CurrentOrientation)
function setup()
    player={x=WIDTH/2,y=HEIGHT/2,radius=50,speed=10}
    stars={}
    starTypes={{value=1,col=color(255),radius=20},{value=2,col=color(255,100,0),radius=30}}
    spawnStar()
    score=0
end

function draw()
    background(0)
    player.x = player.x + Gravity.x*player.speed--move the player in both axis
    player.y = player.y + Gravity.y*player.speed

    for i=#stars,1,-1 do
        local playerPos=vec2(player.x,player.y)
        local starPos=vec2(stars[i].x,stars[i].y)
        local distance=playerPos:dist(starPos)--distance between star and player

        if distance<player.radius+starTypes[stars[i].Type].radius then--if the distance between player and star is less than the sum if their radii then they have collided
            score = score + starTypes[stars[i].Type].value--update cpscore based on type of star
            print("you've got "..score.." points\nWell done")
            table.remove(stars,i)--delete this star
            spawnStar(1)--spawn 1 new star
            --make a sound ir something here:

        end
    end

    noTint()
    spriteMode(RADIUS)
    sprite("Planet Cute:Character Boy",player.x,player.y,player.radius)--draw the player

    for k,s in ipairs(stars) do
        tint(starTypes[s.Type].col)
        sprite("Planet Cute:Star",s.x,s.y,starTypes[s.Type].radius)--draw the star
    end
end

function spawnStar(n)
    local num
    if n then num=n else num=1 end
    for i=1,num do
        local star={x=math.random(50,WIDTH-50),y=math.random(50,HEIGHT-50),num=#stars+1,
                    Type=math.random(1,2)}
        table.insert(stars,star)
    end
end

SkyTheCoder

@Coder

local num
if n then
    num = n
else
    num = 1
end

can be compacted to

local num = n or 1

(which could also be merged into the for loop)

for i = 1, n or 1 do
    ...
end

Coder

@SkyTheCoder yeah that makes the code shorter

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