DM1 V1 — Creature AI Behavior

Status

RESOLVED for DM1 finish scope — movement, perception, reactions, and caster payloads gated

pass1066 gates the F0798/F0799 one-step movement selector. pass1067 gates F0790-F0796 perception, aggro transition, deterministic tick behavior, and champion target selection. pass1069 extends the creature-AI source-lock gate with reaction-event creation, projectile-hit search turning, and danger-on-square movement that stops attack behavior and returns the group to approach. Existing projectile/caster gates cover F0207/F0212 launch payloads, Vexirk alternate spell selection, Wizard Eye/Trolin-style spell palettes, and the C25/C26 BUG0_13-safe fallback.

Runtime creature-chain capture remains tracked separately under the Creature grouping/coordination and original-capture rows; it is not an unimplemented AI-rule gap.

Source-locked to: ReDMCSB WIP20210206 GROUP.C, DEFS.H Companion: src/dm1/dm1_v1_creature_ai_behavior_pc34_compat.c

1. Behavior State Machine

Creatures use a per-group Behavior enum (GROUP.C:1372–1378, DEFS.H):

Values C2–C4 (USELESS) are declared but never assigned (GROUP.C:329, 476 note BUG0_00).

Behavior is stored per-group (Group->Behavior), not per-creature, but individual creatures fire separate UPDATE_BEHAVIOR_CREATURE_N events (38–41) for per-creature attack timing (GROUP.C:2126–2127).

2. Behavior Transition Logic (GROUP.C F0209 GROUP_ProcessEvents29to41)

Wandering (C0) — lines 2100–2148

WANDER ├─ See party? (F0200_GetDistanceToVisibleParty > 0) │ ├─ In attack range? → BEHAVIOR_ATTACK (C6) │ └─ Not in range? → BEHAVIOR_APPROACH (C7) └─ No sight ├─ Smell party? (F0201 + smell range check) │ └─ Try primary dir → possible move → WANDER or same dir └─ No smell └─ Random direction walk (M004_RANDOM(4) + movement possible test)

Approach (C7) — lines 2236–2256

• Same Manhattan distance check as WANDER, but path-found condition succeeds.
• If creature can see party while approaching → transitions to ATTACK (C6).
• If path lost → falls back to WANDER (C0).

Attack (C6) — lines 2073–2134, 2376–2410

• Melee (attack range == 1): F0207_GROUP_IsCreatureAttacking, quarter-square cell adjustment.
• Ranged (attack range > 1): checks alignment (same row or column), F0207 line 1695 branch → projectile creation via F0212_PROJECTILE_Create.
• Giggler special: F0193_GROUP_StealFromChampion — steals random item slot, then flees (C5) with 3/4 probability.
• Quarter-square creatures shift cells before attacking; back-row attackers have 3/4 chance to stay in back row.

Flee (C5) — lines 2289–2308, 2336–2340

• Triggered by: Giggler steal, danger on square, taking damage when HP low.
• Uses F0201 primary direction as opposite (flee from target, not toward).
• T0209094 label: tries primary dir → secondary → opposite-primary → opposite-secondary → give up and fall through to WANDER (C0).

3. Event System

Timeline drives all behavior. Key events (DEFS.H:956–960):

• C37_EVENT_UPDATE_BEHAVIOR_GROUP — recalculate group-wide behavior
• C38..C41_EVENT_UPDATE_BEHAVIOR_CREATURE_0..3 — per-creature attack timing

Reaction events (GROUP.C F0209 C29..C31):

• C29: danger on the group’s square — move away from the danger
• C30: hit by a projectile — probabilistic search/avoidance reaction
• C31: party adjacent — bump/physical-hit reaction; force ATTACK when the creature is eligible and is neither already attacking nor fleeing
• C32..C36: aspect update events (visual only)

Events are accumulated even when Life is Frozen (BUG0_14 noted at GROUP.C:1982).

4. Creature Type Attributes

Creature attributes in Ranges struct (DEFS.H):

• M054_SIGHT_RANGE / M055_SMELL_RANGE / M056_ATTACK_RANGE macros
• SIDE_ATTACK flag (0x0004): creature can see/attack in all 4 directions
• ATTACK_ANY_CHAMPION flag (0x0010): creature can target any party member
• PREFER_BACK_ROW flag: attackers that stay in back row when possible

Creature properties from DATA.C creature tables:

• Wariness (0–15+): higher = more cautious, avoids teleporters
• Movement speed: ticks per move/animation cycle
• Attack damage, attack range, attack type (melee/ranged)

5. Key Source Citations