Game Development Reference
In-Depth Information
1:
{
2:
switch ( direction )
3:
{
4:
case 0: sprite_index = spr_mummy_right; break;
5:
case 90: sprite_index = spr_mummy_up; break;
6:
case 180: sprite_index = spr_mummy_left; break;
7:
case 270: sprite_index = spr_mummy_down; break;
8:
}
9:
image_speed = path_speed/8;
10:
}
Using a
switch
statement, we check the direction and change the sprite accordingly: a
value of
0
means we're going to the right,
90
is upward,
180
is left, and
270
is downward.
Finally, we set the sprite's animation to be relative to the path speed. This means that if
you ever change the path speed, the animation pace changes as well.
10.
Right-click this
Execute a piece of code (Execute Code)
action and select
Copy
from
the context menu. Now open
obj_scorpion
, add a
Step
,
Step
event, right-click in the
Actions
list, and select
Paste
. Next, open the event and replace every occurrence of
mummy
with
scorpion
, and set
image_speed
to
path_speed/4
.
Result:
Reference/Result/patrolling_enemies1.gmk
It's easy to make more than one enemy share a path, so that a particular area is patrolled
more heavily.
Putting Multiple Enemies on a Single Path
1.
Open
room_test
and place three other instances of
obj_scorpion
in the room.
2.
Hold the Control key and right-click the first of the new instances of
obj_scorpion
.
Select
Creation Code…
from the menu and insert the following lines:
1:
{
2:
path_start(path_scorpion1,2,1,true);
3:
path_position = 0.25;
4:
}
The path position indicates where on the path this instance should be placed, a
number between 0 and 1 inclusive. If not specified, it defaults to 0 (the start of the
path). We set it at
0.25
, which means it is a quarter of the way along the path.
3.
Set similar creation codes for the third and the fourth instance, with path positions at
0.5
and
0.75
, respectively.
Result:
Reference/Result/patrolling_enemies2.gmk
If you've been watching the different enemies long enough, you may have noticed that they
sometimes walk into each other. The easy solution to this, of course, is to make sure the paths
never cross. If that's not always an option, we can make sure that enemies check ahead for a
possible collision, and turn around if necessary.
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