Candy::FiniteStateMachine Class Reference

The FiniteStateMachine node provides state machine functionality through programmable states and transitions. More...

Inheritance diagram for Candy::FiniteStateMachine:

Classes
struct	StateId
struct	StateIds
struct	StateName
struct	StateNames

Public Member Functions
	FiniteStateMachine (H3D::Inst< H3D::SFNode > _metadata=0, H3D::Inst< H3D::MFString > _url=0, H3D::Inst< StateId > stateId=0, H3D::Inst< StateIds > stateIds=0, H3D::Inst< StateName > stateName=0, H3D::Inst< StateNames > stateNames=0, H3D::Inst< H3D::SFBool > deterministic=0, H3D::Inst< H3D::SFBool > persistent=0)
void	initialize ()
Public Member Functions inherited from H3D::H3DDynamicFieldsObject
virtual bool	addField (const string &name, const Field::AccessType &access, Field *field)
virtual bool	removeField (const string &_name)
virtual void	clearFields ()

Public Attributes
std::auto_ptr< H3D::SFInt32 >	stateId
	The id of the first active state. More...
std::auto_ptr< H3D::MFInt32 >	stateIds
	The id of all active state. More...
std::auto_ptr< H3D::SFString >	stateName
	The name of the first active state. More...
std::auto_ptr< H3D::MFString >	stateNames
	The names of all active states. More...
std::auto_ptr< H3D::SFBool >	deterministic
	When true, only one state is active at a time. More...
std::auto_ptr< H3D::SFBool >	persistent
	When true, a state will continue to be active when no path is active, otherwise it will die. More...

Static Public Attributes
static H3D::H3DNodeDatabase	database

Friends
struct	StateNames

Detailed Description

The FiniteStateMachine node provides state machine functionality through programmable states and transitions.

A state machine takes care of states in anything from compiler programs, file readers and client/server systems to games and applications. A state can be, for example, 'showing menu', 'running game' or 'game over'. By using a central state machine each functionality of the game or application can be individually programmed in separate scripts or systems and by simply reading of the state value, or even recieve events from the state machine, each script can know what to do, if is should be inactive or start doing something.

This node reads a specified XML file with state and transition specifications. Each state is given a specific number id and a string name. This state id or name can be routed from the stateId and stateName fields. If the state machine is non-deterministic multiple states may be active, in which case the full list of ids and names can be routed from the stateIds and stateNames fields.

XML syntax

Here is a reference manual over the XML syntax of the configuration file read by this node. A strict syntax description can be found in the DTD file.

• automation, the root, containing instances of state and transition
• state, specifies a state, requires an id or name attribute. May contain one or several event tags
  • Attributes:
    • type, the type of the state. One of: normal (default), start (the initial state) or accept (final state)
    • id, a numerical identification
    • name, a string identification
• transition, a (conditioned) transition from one state to another. Should contain a condition and may contain an event. If there is no condition, this transition will always be active
  • Attributes:
    • from, the id or name of the state this transition is from
    • to, the id or name of the state this transition is to
• event, an event producing some output, must have at least field and type, and either field2 or value specified
  • Attributes:
    • trigger, the trigger that activates the output. One of: entry (activated when the state is entered, default), exit (triggered when the state is left), start (triggered if the state is born), or accept (triggered if the state dies)
    • field, the output field that is set to a value by this event
    • field2, the value of this field is copied to the output field, if present
    • value, this value is copied to the output field, if field2 is not specified
    • type, the type of the output (and input) field(s). One of: "string", "int", "float", "double" or "bool"

Conditions

• Boolean operations, have no attributes. Must contain other conditional tags
  • Tags: and, or, xor, not
• Field comparison, compares two input fields or one field with a constant value
  • Tags: eq (equal), leq (less or equal), geq (greater or equal), gt (greater than), lt (less than)
  • Attributes:
    • type, the type of the field(s) to be compared. One of: string, int, float, double or bool
    • field, the field to compare
    • field2, the field to compare with (optional)
    • value, the value to compare with (optional)
• timer, provides a delay controlled condition
  • Attributes:
    • delay, the delay before this condition becomes true
    • field, an SFFloat field with output value between zero and one over the delay of this timer

X3D Interface
	Name	Type	Default value	Description
	url	MFString	""
	stateId	SFInt32
	stateIds	MFInt32
	stateName	SFString
	stateNames	MFString
	deterministic	SFBool	True	In a deterministic state machine only one state is active at a time, but in non-deterministic machines every valid state is active at the same time.
	persistent	SFBool	True	If the state machine is persistent, states will not die when no transition is available.
	(varying)		""|0|false	Every event type connected to a state will provide an outgoing field.
	(varying)		""|0|false	Every transition condition will provide at least one incoming field. Multiple transitions can also be controlled from the same fields.

Member Data Documentation

std::auto_ptr< H3D::SFBool > Candy::FiniteStateMachine::deterministic

When true, only one state is active at a time.

A non-deterministic state-machine (deterministic = false) will have all valid states active at the same time.

std::auto_ptr< H3D::SFBool > Candy::FiniteStateMachine::persistent

When true, a state will continue to be active when no path is active, otherwise it will die.

std::auto_ptr< H3D::SFInt32 > Candy::FiniteStateMachine::stateId

The id of the first active state.

Use this for a deterministic state-machine.

std::auto_ptr< H3D::MFInt32 > Candy::FiniteStateMachine::stateIds

The id of all active state.

std::auto_ptr< H3D::SFString > Candy::FiniteStateMachine::stateName

The name of the first active state.

Use this for a deterministic state-machine.

std::auto_ptr< H3D::MFString > Candy::FiniteStateMachine::stateNames

The names of all active states.