Game Development Reference
In-Depth Information
image_blend
is a color applied to the sprite when it is drawn. It is set to
c_white
by
default, and using different values will change the color of the sprite when it is drawn.
You can only change this variable in the registered, Pro version of Game Maker 8.
•
visible
determines whether the object is visible or invisible (
true
or
false
).
•
solid
determines whether the object is treated as solid in collisions (
true
or
false
).
•
•
persistent
determines whether the object will continue to exist in the next room, or
whether it remains part of the room in which it was originally created (
true
or
false
).
Note
The constants
true
and
false
correspond to the values
1
and
0
, respectively.
These two variables hold information about the identity of the instance:
•
id
is a unique identifying number that distinguishes the current instance from any
other.
•
object_index
is the index of the object resource that the current instance is an
instance of.
There are also a number of other variables that you cannot change, but are maintained
internally by Game Maker
for each instance depending on the current sprite. So you can check to
see what values these variables hold (using a
Test Variable
action, for example), but you cannot
change them (using a
Set Variable
action):
•
sprite_width
is the width of the current sprite displayed for the instance.
sprite_height
is the height of the current sprite displayed for the instance.
•
•
sprite_xoffset
is the x position of the origin within the sprite.
sprite_yoffset
is the y position of the origin within the sprite.
•
•
image_number
is the number of images in the current sprite.
•
bbox_left
is the x coordinate of the left edge of the sprite's bounding box in the room.
•
bbox_right
is the x coordinate of the right edge of the sprite's bounding box in the
room.
bbox_top
is the y coordinate of the top edge of the sprite's bounding box in the room.
•
bbox_bottom
is the y coordinate of the bottom edge of the sprite's bounding box in the
room.
•
Variables in Other Instances
You usually refer to an instance's variables within its own actions by entering their names in their
basic form, as provided previously. Using actions to set or test an instance's variables in this way
will only affect the instance concerned (hence, they are local to the instance). However, you can
also refer to variables in other instances by using an object name followed by a dot (period/full-
stop) and then the variable name (for example,
obj_dragon.x
). Used within a
Test Variable
action,
this would retrieve the x position of the first instance of
obj_dragon
that was placed in the room
(disregarding any other instances of
obj_dragon
). However, used within a
Set Variable
action, it
would change the x position of
all
the instances of
obj_dragon
in the game—so be careful.
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