Scratch

bullelk12 · 2012-07-31 13:28:59

I'm working on a type of tower defense game and I need the enemies to move across the map towards a castle. But they can't move through any walls, over any mountains etc. I know there's a way to do it but the scripts are astronomically large. Is there a way to do this.

BirdByte · 2012-08-01 03:23:56

I'll look into this further and post a script. smile

BirdByte · 2012-08-01 03:30:41

Well, the best way to do this is by mapping it out manually. Here is an example:

repeat (240)
 change x by (1)
end
repeat (20)
 change y by (1)
end
repeat (180)
 change x by (1)
end
repeat (20)
 change y by (-1)
end
repeat (60)
 change x by (1)
end

If your path needs to be AI, computing the shortest unblocked way, I have a few questions:

Are your mountains/walls separate sprites, or are they part of the stage?
Is your map simple enough for the touching color blocks to be usable?
Are you trying to make this 1s1s?

joefarebrother · 2012-08-01 04:49:20

Well you could have a preset list of directions in a format

direction
steps
direction
steps...

and then a script

set [index v] to [1]
go to x:(start x) y:(start y)
point in direction (start direction)
repeat (length of [path list v])
  turn left (item (index) of [path list v]) degrees
  change [index v] by (1)
  move (item (index) of [path list v]) steps
  change [index v] by (1)
end

and then to generate the paths, make a sprite shaped like an arrowhead and a local variable called current action and do

when gf clicked
delete (all v) of [path list v]
set [current action v] to [turn]
add [0] to [path list v]
go to x:(start x) y:(start y)
point in direction (start direction)

when key [up arrow v] pressed
move (1) steps
if <(current action) = [move]>
  replace item (last v) of [path list v] with ((item (last v) of [path list v]) + (1))
else
  set [current action v] to [move]
  add [1] to [path list v]
end

when key [down arrow v] pressed
move (-1) steps
if <(current action) = [move]>
  replace item (last v) of [path list v] with ((item (last v) of [path list v]) - (1))
else
  set [current action v] to [move]
  add [-1] to [path list v]
end

when key [left arrow v] pressed
turn left (1) degrees
if <(current action) = [turn]>
  replace item (last v) of [path list v] with ((item (last v) of [path list v]) + (1))
else
  set [current action v] to [turn]
  add [1] to [path list v]
end

when key [right arrow v] pressed
turn right (1) degrees
if <(current action) = [turn]>
  replace item (last v) of [path list v] with ((item (last v) of [path list v]) - (1))
else
  set [current action v] to [turn]
  add [-1] to [path list v]
end

You can delete this sprite after the path has bees generated, or just hide it and detach the when key pressed blocks from their scripts so you could use it again later.

Prestige · 2012-08-01 16:22:48

I also like the list suggestion. You could also expand it to make it more advanced by allowing enemies of different speeds.

Use this simple equation to work out the time taken by a sprite of a known speed over a known distance - time = distance/speed.

So:

1) Add all your positions for the AI to a list, add them as x position, y position.

(In this example, my points are (150, 0), (20,40), (0,0)...)

add (150) to [list v]
add (0) to [list v]
add (20) to [list v]
add (40) to [list v]
add (0) to [list v]
add (0) to [list v]

2) Now, we'll need to move to the next point. You might also want the enemy to point towards the position that they're moving to. For that, see this tutorial on how to make a sprite point towards a co-ordinate.

set [counter v] to (1)
set x to (item (counter) of [list v])
set y to (item ((counter) + (1)) of [list v])
Change [counter v] by (2)
Repeat (((length of [list v]) / (2)) - (1))


Set [distance v] to (Sqrt((((X position) - (item (counter) of [list v]) * (X position) - (item (counter) of [list v])) + ((Y position) - (item ((counter) + (1)) of [list v]) * (Y position) - (item ((counter) + (1)) of [list v])))))


Glide ((distance) / (speed)) secs to x: (item (counter) of [list v]) y: (item ((counter) +(1)) of [list v])
change [counter v] by (2)
end

Last edited by Prestige (2012-08-01 16:27:45)

Wes64 · 2012-08-01 16:34:45

Prestige wrote:

set [counter v] to (1)
set x to (item (counter) of [list v])
set y to (item ((counter) + (1)) of [list v])
Change [counter v] by (2)
Repeat (((length of [list v]) / (2)) - (1))


Set [distance v] to ([sqrt v] of ((((X position) - (item (counter) of [list v])) * ((X position) - (item (counter) of [list v]))) + (((Y position) - (item ((counter) + (1)) of [list v])) * ((Y position) - (item ((counter) + (1)) of [list v])))))


Glide ((distance) / (speed)) secs to x: (item (counter) of [list v]) y: (item ((counter) +(1)) of [list v])
change [counter v] by (2)
end

fixed