Scratch

There's really no such thing as simple pathfinding.  You generally stuck with needing some kind of recursion.  I have found a way to do it without recursion in a generally straight-forward way.  You have to essentially cover the entire field with ghosted rectangles, in which every rectangle can get to any point in an adjacent rectangle using a straight-line path.

Example (gray spots are walls, colored rectangles are the "invisible" rectangles):


Then, to circumvent the recursion algorithm, you have to manually create a list of "if I am in rectangle X and I want to get to rectangle Y, I should point at rectangle Z".  Once the sprite is in the rectangle it wants to be in, it can take a straight-line path to the exact point.  This approach can take a very long time to program if you have a lot of rectangles, but it gets the job done.

Edit: the ability to import lists can come in handy, as it is easier to type up these incredibly long lists than to manually create them.

Last edited by MoreGamesNow (2012-08-18 12:05:19)

Ok but i mean e.g a pac man ghost that follows a pacman using tiles

BirdByte wrote:

All AIs are different. Try this.

forever
Replace this with your loop...
delete 
all  ▼
 of 
paths ▼
change x by 
20
Width of path.
if 
touching 
walls ▼
?
add 
100000
 to 
paths ▼
else
add 
distance to 
player ▼
 to 
paths ▼
change x by 
-20
Width of path, negative.
change y by 
-20
Width of path, negative.
if 
touching 
walls ▼
?
add 
100000
 to 
paths ▼
else
add 
distance to 
player ▼
 to 
paths ▼
change y by 
20
Width of path.
change x by 
-20
Width of path, negative.
if 
touching 
walls ▼
?
add 
100000
 to 
paths ▼
else
add 
distance to 
player ▼
 to 
paths ▼
change x by 
20
Width of path.
change y by 
20
Width of path.
if 
touching 
walls ▼
?
add 
100000
 to 
paths ▼
else
add 
distance to 
player ▼
 to 
paths ▼
change y by 
-20
Width of path, negative.
delete 
all  ▼
 of 
directions ▼
add 
1
 to 
directions ▼
add 
2
 to 
directions ▼
add 
3
 to 
directions ▼
add 
4
 to 
directions ▼
set 
sorted ▼
 to 
0
repeat until 
sorted
 = 
1
set 
sorted ▼
 to 
1
set 
counter ▼
 to 
1
repeat 
3
if 
item 
counter
 of 
paths ▼
 > 
item 
counter
 + 
1
 of 
paths ▼
set 
sorted ▼
 to 
0
set 
temp ▼
 to 
item 
counter
 + 
1
 of 
paths ▼
replace item 
counter
 + 
1
 of 
paths ▼
 with 
item 
counter
 of 
paths ▼
replace item 
counter
 of 
paths ▼
 with 
temp
set 
temp ▼
 to 
item 
counter
 + 
1
 of 
directions ▼
replace item 
counter
 + 
1
 of 
directions ▼
 with 
item 
counter
 of 
directions ▼
replace item 
counter
 of 
directions ▼
 with 
temp
change 
counter ▼
 by 
1
point in direction 
90
 * 
item 
1  ▼
 of 
directions ▼
move 
20
 steps
Width of path.
point in direction 
90  ▼

Oops! Fixed. Use this one instead. 

Jodymoses wrote:

And you use it in...

The enemy sprite.

Isn't paths not going to any use because no motion blocks are used?

Jodymoses wrote:

Isn't paths not going to any use because no motion blocks are used?

What do you mean by no motion blocks used? I see several...

Is it?

I'm not going to try to understand the script, but it seems that "paths" affects "directions", which affects movement:

point in direction 
90
 * 
item 
1  ▼
 of 
directions ▼
move 
20
 steps

Jodymoses wrote:

Is it?

"Paths" are lists, under "Variables".

Why do you add the below?

when  clicked
if 
touching {walls}
add 
10000
 to Paths

Bump