Spawn anywhere accept certain positions.

Games
#1

*** Title supposed to be ’ Except certain positions’ and not ’ Accept’ *** sorry for that mistake

I’m wondering if its possible to have a table of coordinates and inside a spawn function that creates a display object, make it exclude those positions inside the table when positioning. 

For example, I have another object that is spawning at these coordinates only…

local yPosition = {100, 160, 220 }

And using them like this when creating an object.

local rnd = math.floor(math.random() \* 3) +1 if(rnd == 0) then gem2 = display.newImageRect("images/obstacle1.png", 90,212) gem2.x = display.contentWidth + 100 gem2.y = yPosition[math.floor(math.random() \* 4)+1]

Is there a way to use something similar to that, but only exclude the positions in yPosition and spawn everywhere else? 

Hope this made sense. 

Cheers.

#2

In your case rnd  will never be 0?  If you want to generate a random number between 1 and 3 use math.random(1,3).

Two ways of approaching your problem.  1) Have an array of allowable spawn points - good if the count of spawn points is low. 2) Check if a spawn point is not being used and then continue.

#3

For for the comment adrianm, I think you might have misunderstood my question which is actually my fault. sorry. 

The snippet from the code including the rnd part was just a demonstration of how I’m using yPosition variable. That function has more rnd values inside the function and works fine. 

I guess the main question is: How can I make a new spawn exclude the values inside yPosition. 

Sorry for the confusion.

#4

Ah OK… was just pointing out what appeared a logic bug (this is the trouble with partial code).

If you want to exclude a range of values do something like this

local yPositions = {100, 160, 220, etc} local yPos = 0 local canPlace, foundSpawnPoint = true, false while not foundSpawnPoint do yPos = math.random(1,240) for i = 1, #yPositions do if yPos == yPositions[i] then canPlace = false break end end if canPlace then foundSpawnPoint = true end end

Note: this is not the most optimal way but I’ve coded it like this so it is easy for you to understand.

#5

Thats perfect. Exactly what I was after and learned something new. Thanks for the help adrianm

#6

In your case rnd  will never be 0?  If you want to generate a random number between 1 and 3 use math.random(1,3).

Two ways of approaching your problem.  1) Have an array of allowable spawn points - good if the count of spawn points is low. 2) Check if a spawn point is not being used and then continue.

#7

For for the comment adrianm, I think you might have misunderstood my question which is actually my fault. sorry. 

The snippet from the code including the rnd part was just a demonstration of how I’m using yPosition variable. That function has more rnd values inside the function and works fine. 

I guess the main question is: How can I make a new spawn exclude the values inside yPosition. 

Sorry for the confusion.

#8

Ah OK… was just pointing out what appeared a logic bug (this is the trouble with partial code).

If you want to exclude a range of values do something like this

local yPositions = {100, 160, 220, etc} local yPos = 0 local canPlace, foundSpawnPoint = true, false while not foundSpawnPoint do yPos = math.random(1,240) for i = 1, #yPositions do if yPos == yPositions[i] then canPlace = false break end end if canPlace then foundSpawnPoint = true end end

Note: this is not the most optimal way but I’ve coded it like this so it is easy for you to understand.

#9

Thats perfect. Exactly what I was after and learned something new. Thanks for the help adrianm