AI Metrics

The majority of this information is for the Half-Life 2 ai.

Introduction

The NPCs in Half-Life 2 have a variety of constraints influencing how they behave and interact. This includes everything from cover search distance to jump height, and as a level designer this information can be quite handy when constructing an encounter. All the distances listed are in Hammer editor units.

Default Metrics

These are the default metrics for the NPCs; information such as jump height can change between different classes.

Squads

Max number of squad members = 16

Jumping

This information applies to jump hint nodes as well.

Max Jump Drop = 192
Max Jump Up = 80
Max Jump Distance = 250

Cover and Line-Of-Sight Acquisition

Crouching eye height (used to test low cover) = 40
Standing eye height = 64
Max cover search distance from NPC = 784
Max Line-Of-Sight search distance from target = 1024
Distance between lateral checks (used for navigation off node graph) = 48
Number of lateral checks (used for navigation off node graph) = 5

Weapon Metrics

This is the information the NPCs use when handling weapons. Minimum and maximum ranges are the distances that the NPC will actually fire the weapon, this can be modified by the long range spawn flag, and sometimes change depending on the running behavior. The accuracy cones for different NPCs are listed here as well,

AR2

Minimum range = 65
Maximum range = 2048
NPC damage = 3
Alt fire decay distance = 2000
NPC alt fire damage to player = 20
Accuracy:
- Default = 3 degrees
- combine soldier = 5 degrees (9 degrees in Half-Life 2)
- citizen = 5 degrees

Pistol

Minimum range = 24
Maximum range = 1500
NPC damage = 3
Accuracy:
- Default = 5 degrees
- metrocop = 12.5 degrees

RPG

Minimum range = 480
Maximum range = 6000

Shotgun

Minimum range = 0
Maximum range = 500
Number of pellets = 8
NPC damage per pellet = 3 (24 damage total)
Accuracy:
- Default = 10 degrees
- Alyx = 3 degrees

SMG1

Minimum range = 0
Maximum range = 1400
Maximum range for allies = 3000
NPC damage = 3
Accuracy:
- Default = 5 degrees
- combine soldier = 16.6 degrees
- metrocop = 8.3 degrees

NPC Specific Metrics

These are specific metrics for NPCs, such as Antlion jump metrics and Combine Soldier grenade distances.

APC Driver

Minimum machine gun range = 0
Maximum machine gun range = 1250
Minimum rocket range = 1250
Maximum rocket range = 5200

Antlion

Max Jump Drop = 512
Max Jump Up = 512
Min Jump Distance = 128
Max Jump Distance = 1024
Worker Eye Height = 96
Worker Minimum Range Attack = 240
Worker Maximum Range Attack = 1800

Antlion Guard

Minimum Charge Distance = 256
Maximum Charge Distance = 2048
Maximum Melee Range = 156
Time Inbetween Charges = 4
Max Possible Summon Distance = 264

Combine Soldier

Height of Shotgun = 36
Minimum grenade distance = 128
Maximum grenade distance = 1024
If an enemy has moved farther than this after taking cover, then don't grenade = 256
Minimum AR2 alt fire distance = 128
Distance at which to ignore squad slots when advancing = 3000
Distance at which tactical variant "Pressure until within 30ft, then normal" switches = 360