Reducing Video Game Creation Effort with Eberos GML2D - Game Development Tools - page 275

19.1.5 Collisions Detection
Currently, the language only models bounding object collision detection with bound-
ing rectangles and bounding circles. An entity in the game model becomes a can-
didateforcollisiondetectionwhena BoundingObject isdefinedforit(see Fig-
ure19.6 ) .Thismeansthatnowtheentitycanbeatargetforactuatorsthatdeal
with collisions, as is the case for the ConditionalActuator CheckCollision .For
Eberos GML2D, we only model two kinds of BoundingObjects : BoundingRectangle
and BoundingCircle .The BoundingRectangle contains information about its
width and height in pixels. Similarly, the BoundingCircle contains information
about the size of its radius in pixels.
19.1.6 Input Handling
In Eberos GML2D, every entity reference is capable of having an InputHandler
construct attached to it. When an entity has an InputHandler ,itmeansthatsuch
an entity is controlled by an input device in some way. At the time this article was
written, InputHandler only models keyboard input.
Keyboard input is modeled by adding a KeyboardKey to the InputHandler con-
struct(see Figure19.7 ) .InEberosGML2D,a KeyboardKey containsthreepieces
of information: the key to detect, the state of the key we are interested in, and
the GameMessage to dispatch when the key and key state are matched. Currently,
there are four possible states that can be modeled: DOWN , RELEASED , WAS_PRESSED ,
and IS_HOLDING . Once the input is matched, that is, the key specified is in the de-
sired state, the entity attached to the InputHandler is notified of the GameMessage
specified for that key. This GameMessage is then used as a link between the entity
logic and the input.
Figure 19.7. Basic class diagram for entity to input relationship.