Antlions: Random Spawn

The great thing about these antlions is that they are made to be used with other litle 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 Antlion entity:

Class: npc_antlion
Keyvalues		Comments
Name	AntLion

with the following flags set:

	Flag
	File:Checkbox-yes.png	Start Burrowed
	File:Checkbox-yes.png	Template NPC

Next, configure an entity that triggers inputs if the player is walking on the specified material:

Class: env_player_surface_trigger
Keyvalues		Comments
Name	SurfaceTrigger
GameMaterialToWatch	sand

and add the following outputs:

		My output	Target entity	Target input	Parameter	Delay	Only once	Comments
	File:Entity-output-iconOnSurfaceChangedFromTarget.png	relay_expanse_disablespawn	Trigger				..if the player starts walking on the surface we have chosen, it triggers the relay OnSurfaceChangedToTarget which enables the npc_antlion_template_maker	{{{8}}}
	File:Entity-output-iconOnSurfaceChangedToTarget.png	relay_expanse_spawn	Trigger				..and after that that when (or if) the player steps off it, it triggers the relay OnSurfaceChangedFromTarget which stops the spawning	{{{8}}}

This entity 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

This entity creates the quake when the antlions are emerging:

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

This entity actually creates 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	t..he target that the antlions will attack
Ignore Bugbait	No

Now, remember to check the following flag:

	Flag
		Infinite Children

Then, add the following output:

		My output	Target entity	Target input	Parameter	Delay	Only once	Comments
	File:Entity-output-iconOnAllSpawnedDead.png	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	{{{8}}}

Add first logic_relay:

Class: logic_relay
Keyvalues		Comments
Name	relay_expanse_spawn

with the following outputs:

		My output	Target entity	Target input	Parameter	Delay	Only once	Comments
	File:Entity-output-iconOnTrigger.png	sound_antlion_spawn	PlaySound				..if this relay is triggered it plays the sound	{{{8}}}
	File:Entity-output-iconOnTrigger.png	relay_expanse_disablespawn	CancelPending					{{{8}}}
	File:Entity-output-iconOnTrigger.png	shake_antlion_spawn	StartShake		0.10		..the ground shakes	{{{8}}}
	File:Entity-output-iconOnTrigger.png	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	{{{8}}}

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
	File:Entity-output-iconOnTrigger.png	sound_antlion_spawn	StopSound				..if this relay is triggered, the sound stops	{{{8}}}
	File:Entity-output-iconOnTrigger.png	shake_antlion_spawn	StopShake				..the shake stops	{{{8}}}
	File:Entity-output-iconOnTrigger.png	antlion_expanse_spawner	Disable		0.50		..and the template_maker disables	{{{8}}}
	File:Entity-output-iconOnTrigger.png	relay_expanse_spawn	CancelPending		0.50			{{{8}}}

Another group of entities are to set where the antlions can spawn, you must put one everywere 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 info_node_air to navigate while flying.

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, put some info_node_airs about 10 units above it, 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:

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:

OnSpawnNpc, AiSchedule, StartSchedule

Example Map

Example map