Antlions: Random Spawn

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The great thing about these antlions is that they are made to be used with other little tools to make them spawn randomly when the player walks on a specified material, be it sand or any other material.

This tutorial will walk you through the making of a simple example of randomly unburrowing antlions.

Getting started

First, make a map with sand and rocks. The situation we are attempting to create is that if the player walks on the sand, antlions come out near the player and attack, and the player is forced to walk on the rocks.

These are the entities we are going to need:

• npc_antlion
• env_shake
• ambient_generic
• npc_antlion_template_maker
• logic_relay
• env_player_surface_trigger
• info_node_hint

Configuring the entities

First create an npc_antlion with the following properties.

Class: npc_antlion
Keyvalues		Comments
Name	AntLion
Start Burrowed	Yes

	Flag
		Template NPC

Next, configure the entity that triggers inputs when the player walks on the sand:

Class: env_player_surface_trigger
Keyvalues		Comments
Name	SurfaceTrigger
GameMaterialToWatch	sand

		My output	Target entity	Target input	Parameter	Delay	Only once	Comments
		OnSurfaceChangedFromTarget	relay_expanse_disablespawn	Trigger				When the player starts walking on the surface we have chosen, this entity triggers the relay OnSurfaceChangedToTarget.
		OnSurfaceChangedToTarget	relay_expanse_spawn	Trigger				When the player steps off it, it triggers the relay OnSurfaceChangedFromTarget

Then you will have to create the entity that creates the noise when the antlions are emerging.

Class: ambient_generic
Keyvalues		Comments
Name	sound_antlion_spawn
SoundName	Streetwar.d3_c17_10b_rumble1
Volume	8
Fade In Time	1.5
Fade Out Time	2
Pitch	120
Start Pitch	90
Max Audible Distance	1250

And the one to create the quake.

Class: env_shake
Keyvalues		Comments
Name	shake_antlion_spawn
Amplitude	2
Effect Radius	500
Duration	3
Frequency	100

The following entity actually creates the antlions.

Class: npc_antlion_template_maker
Keyvalues		Comments
Name	antlion_expanse_spawner
StartDisabled	Yes	We do not want the template_maker to start spawning at the beginning of the map.
Num. of NPCs		Leave empty because we will check Infinite Children in flags.
Frequency	0.35
Max Live NCPs		How many antlions can live at same time, 8 for example.
Name Of Template NPC	AntLion
Spawn On HintGroup	antlion_expanse_spawn_nodes
Spawn Radius	1000
Spawn Target	!player	The target that the antlions will attack.
Ignore Bugbait	No

	Flag
		Infinite Children

		My output	Target entity	Target input	Parameter	Delay	Only once	Comments
		OnAllSpawnedDead	antlion_expanse_spawner	SetMaxChildren	8	9.00		..that means if all antlions are dead it resets the max number to 8 to prevent any problems

Add the first logic_relay:

Class: logic_relay
Keyvalues		Comments
Name	relay_expanse_spawn

		My output	Target entity	Target input	Parameter	Delay	Only once	Comments
		OnTrigger	sound_antlion_spawn	PlaySound				When this relay is triggered it plays the sound.
		OnTrigger	relay_expanse_disablespawn	CancelPending
		OnTrigger	shake_antlion_spawn	StartShake		0.10		The ground shakes.
		OnTrigger	antlion_expanse_spawner	Enable		1.00		And the npc_antlion_template_maker enables 1 second after we walked on the ground, which makes an effect like the antlions are coming up.

Add another logic_relay...

Class: logic_relay
Keyvalues		Comments
Name	relay_expanse_disablespawn

with the following outputs:

		My output	Target entity	Target input	Parameter	Delay	Only once	Comments
		OnTrigger	sound_antlion_spawn	StopSound				When this relay is triggered, the sound stops.
		OnTrigger	shake_antlion_spawn	StopShake				Also, the shake stops..
		OnTrigger	antlion_expanse_spawner	Disable		0.50		..and the template_maker disables
		OnTrigger	relay_expanse_spawn	CancelPending		0.50

Another group of entities are to set where the antlions can spawn, you must put one everywhere that the antlion can possibly spawn, and the npc_antlion_template_maker will pick the one nearest the player.

Class: info_node_hint
Keyvalues		Comments
Hint	AntLion Burrow Point
Hint Group	antlion_expanse_spawn_nodes

Notes

The antlions use info_node to navigate on the ground, and "fly" by using loose jump parameters.

To make them follow a precise path, use path_corners and set it to the antlion's path corner, and place info_nodes around the way so the antlions can navigate through them.

If there is a wall in their way, make sure there is a jump connection, and the antlions will use it to fly above the wall.

Quick tutorial to making antlions follow a path

If you want the antlions to run to a precise target, use aiscripted_schedule, name it and configure:

Class: aiscripted_schedule
Keyvalues		Comments
Target Npc	Antlion
Search Radius		..if there are more than one target, put 0.
All In Radius		..if there are more than one target, put yes.
Ai State To Set		..choose one
Schedule to run		..choose one
Interruptability		..choose one
Goal Entity		..is the target, it can be one precise or a classname, like npc_citizen

Then at the npc_antlion_template_maker, add the following output:

		My output	Target entity	Target input	Parameter	Delay	Only once	Comments
		OnSpawnNpc	AiSchedule	StartSchedule