+ The basic Whirled services facilitate a game that provides a + connected set of scenes and the ability for the bodies to move from + a scene to its neighboring scenes. The Spot package extends those + services by providing the notion of locations within scenes which a + body can occupy and which, while occupied, cannot be occupied by + other bodies. +
+ +The philosophy is that a game that uses these services wants to + create a constrained universe where a body cannot simply stand + anywhere on the screen, but can only stand in a set of predefined + locations. This is a simplified mechanism for providing finer + grained locality management, such that expensive distance monitoring + algorithms need not be used to determine who can interact (speak) + with others in a particular scene. For many games, the overhead of + tracking each users' position in near-realtime coupled with a + complex message broadcasting system that dispatches messages to + users in geometric proximity to one another is serious overkill and + does not add sufficient value to the game to merit inclusion. +
+ +Locations and clusters
+
+ The Spot package provides a functional approximation in the form of
+ clusters of locations, with predefined coordinates, that are
+ sufficiently proximal that bodies in that cluster of locations can
+ all speak to one another. The locations for a particular scene are
+ specified in advance which serves the additional purpose of putting
+ a limit on the number of bodies that can be standing (and
+ participating) in a particular scene. This puts a natural upper
+ bound on the amount of network traffic that will be generated by the
+ need to broadcast scene updates to all occupants of a scene.
+
Locations also serve as entry and exit points for a scene, + providing a means both for the graphical user interface to identify + the location at which bodies enter and exit a scene as well as + providing a spatial context for the connections between scenes + (i.e. the exit to the scene to the north can be located in the + northward part of a scene display). +
+ +Orientation
+
+ Locations define a notion of orientation which is assigned a priori,
+ along with the coordinates of the location and which can be
+ interpreted by the graphical display as the direction that body
+ sprites should face when standing on that location. Clusters of
+ locations can be constructed such that all of the bodies standing in
+ that cluster appear to be facing one another which provides visible
+ reinforcement that members of the cluster can "hear" the
+ conversation, while members of other clusters cannot. The
+ orientation of entry and exit locations are also useful in
+ establishing an initial orientation for a body sprite that enters a
+ scene based on the visualization of the entrance mechanism (i.e. if
+ they appear to enter through the door, the body sprite should be
+ oriented as if it just walked in the proper direction through the
+ door).
+
Because the Spot services redefine the scope at which speak + messages are normally distributed (the Crowd services would, by + default, have speak messages dispatched to everyone in the entire + scene because the scene is a place and the default chat mechanisms + dispatch speak messages to all occupants of a place), it defines an + additional communication mode known as shouting, which conveys the + message to everyone in the entire scene. +
+ +Portals
+
+ Portals are a combination of locations and the standard Whirled
+ notion of neighboring scenes. They contain the coordinates to which
+ a body sprite would traverse prior to exiting to a neighboring scene
+ (generally so that they appear to walk to whatever visual
+ representation of the portal is provided by the scene, like a door
+ or perhaps simply the edge of the scene). Conversely, they represent
+ the coordinates at which a body arriving from same neighboring scene
+ would appear in the displayed scene.
+
Example display
+
+ This is an example of how these concepts might look in a game
+ providing top-down 2D display of its scenes.
+
+ The arrows would, of course, not be rendered but are shown to + indicate the presence of locations (and portals) and their + associated orientation information. +
+ + +