Creating a condition

Declaration

The first step to creating a condition for your NPC is to create a name for it and add it to the enum. Here's an example name for a condition: COND_BLOCKED_BY_DOOR.

Once the condition is added to the enum, you must use the DECLARE_CONDITION macro in the AI_BEGIN_CUSTOM_NPC section.

Here's an example of the DECLARE_CONDITION code:

	DECLARE_CONDITION( COND_NEWNPC_CONDITION )

Note:It is not necessary to declare shared conditions.

GatherConditions

GatherConditions can be overridden in child classes to implement the selection of custom conditions; the function sets the NPC's conditions appropriate at the time based on game state.

The following condition has been taken from the headcrabs GatherConditions() method.

if( m_lifeState == LIFE_ALIVE && GetWaterLevel() > 1 ) 
{ 
          // Start Drowning! 
         SetCondition( COND_HEADCRAB_IN_WATER ); 
} 

This if block checks to see if the headcrab is alive but submerged in water, if so a condition COND_HEADCRAB_IN_WATER is set.

BuildScheduleTestBits

BuildScheduleTestBits can be overridden to set custom condition to interrupt schedules. If you want to see your NPC react to conditions, this needs to be overriden so the NPC reacts to fire (COND_ON_FIRE) or starts drowing (COND_HEADCRAB_IN_WATER) right away, not after the current schedule ends.

Here is code from the headcrabs BuildScheduleTestBits()

if ( !IsCurSchedule(SCHED_HEADCRAB_DROWN) )
{
	// Interrupt any schedule unless already drowning.
	SetCustomInterruptCondition( COND_HEADCRAB_IN_WATER );
}
else
{
	// Don't stop drowning just because you're in water!
	ClearCustomInterruptCondition( COND_HEADCRAB_IN_WATER );
}

If the condition COND_HEADCRAB_IN_WATER is set, it interrupts the current schedule unless it is already drowning. Then this is handled in SelectSchedule() to choose the appropriate schedule (SCHED_HEADCRAB_DROWN) that will end up drowning the headcrab.

See also

• Conditions
• Shared conditions

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Creating an NPC

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