Mutant Monster Vortigaunt

1. Mutant Monster Vortigaunt Ming Yang

2. Outline • Goal: • Crazy monster: vortigaunt • Custom NPC • Sub-system of AI • NPC vortigaunt • Damage system • Demo

3. Goal • To implement a crazy monster that attacks the player violently. • To implement a custom NPC based on custom modeling.

4. Challenges • The AI and NPC systems are huge. • The functionalities are distributed in the class hierarchy tree. Some latent constraints are hard to find.

5. Results • Convert the friendly ally monster vortigaunt into a crazy killer. • Create a custom NPC npc_cube based on Zach’s modeling (why it cannot think?)

6. NPC vortigaunt • Capable of range attack and melee attack, a loyal friend of the player that attacks the player’s enemy and heal the player. • Set the player to be the enemy of vortigaunt is forbidden. • The damage of vortigaunt’s attack to the player will be filtered.

7. Custom schedule • Detect the player and trigger the attack • Add modules in SelectSchedule(). • Implement 2 kinds of custom schedules: • SCHED_VORTIGAUNT_MELEE_ATTACK_PLAYER • SCHED_VORTIGAUNT_RANGE_DODGE

8. Damage System • Class CTakeDamageInfo wraps the damage info including the attacker, damage, damage force, damage position et al. • Attacker generates CTakeDamageInfo objects and calls the victim’s TakeDamage() to send the damage and the victim responses it in OnTakeDamage().

9. Damage filter • The damage sent to the player will be filtered in • CBasePlayer::TraceAttack • CBasePlayer::OnTakeDamage • CHL2_Player::PassesDamageFilter • CTeamplayRules will test if the attacker is teammate or ally. • g_pGameRules->FPlayerCanTakeDamage • CTeamplayRules::FPlayerCanTakeDamage

10. Demo • Run run_mod.bat • Test the npc with console commands: • Npc_create npc_vortigaunt • Npc_create npc_cube