Enemy-motion-aware bullet simulation #122

New Issue

2026-08-29T19:04:14+02:00

SirStone commented

2026-08-29 19:04:14 +02:00

What to build

Fix the enemy-motion snapshot error by interpolating enemy position at bullet arrival time in the virtual bullet tracker.

Currently all 64 virtual bullets in a generation use the same enemy position snapshot from onScannedBot. Bullets travel for 5-100 ticks, but the simulation checks hit/miss against the current enemy position, not where the enemy will be when the bullet arrives.

Acceptance criteria

stepBullets accepts enemyVx, enemyVy parameters
stepBullets computes interpolated enemy position: enemyX + enemyVx * arrivalTicks
spawnBullet calculates arrivalTicks = ceil(distance / bulletSpeed) and passes velocity
Enemy velocity is threaded from onScannedBot (which already computes e.speed and e.direction)
For stationary enemies (zero velocity), behavior is identical to current implementation
Fitness scores are more accurate for moving targets
Existing hit detection geometry tests still pass

Blocked by

Tracker extraction (#121) - the VBulletEnvironment type must exist before we change its API

Parent

Closes part of #118

## What to build Fix the enemy-motion snapshot error by interpolating enemy position at bullet arrival time in the virtual bullet tracker. Currently all 64 virtual bullets in a generation use the same enemy position snapshot from onScannedBot. Bullets travel for 5-100 ticks, but the simulation checks hit/miss against the current enemy position, not where the enemy will be when the bullet arrives. ## Acceptance criteria - stepBullets accepts enemyVx, enemyVy parameters - stepBullets computes interpolated enemy position: enemyX + enemyVx * arrivalTicks - spawnBullet calculates arrivalTicks = ceil(distance / bulletSpeed) and passes velocity - Enemy velocity is threaded from onScannedBot (which already computes e.speed and e.direction) - For stationary enemies (zero velocity), behavior is identical to current implementation - Fitness scores are more accurate for moving targets - Existing hit detection geometry tests still pass ## Blocked by Tracker extraction (#121) - the VBulletEnvironment type must exist before we change its API ## Parent Closes part of #118

SirStone added the ready-for-agent label 2026-08-29 19:05:49 +02:00

SirStone closed this issue

2026-08-29 20:17:45 +02:00

SirStone commented

2026-08-29 20:17:46 +02:00

Implemented in commit a730a9e

Summary: Fixed enemy-motion snapshot error by interpolating enemy position at bullet arrival time. stepBullets now accepts enemyVx, enemyVy and computes interpolated position: enemyX + enemyVx * arrivalTicks. spawnBullet calculates arrivalTicks = ceil(distance / bulletSpeed).

Files:

vapourbot_garage/src/vapourbot/gun.nim - stepBullets signature, interpolation logic, spawnBullet arrival calculation

Implemented in commit a730a9e **Summary:** Fixed enemy-motion snapshot error by interpolating enemy position at bullet arrival time. stepBullets now accepts enemyVx, enemyVy and computes interpolated position: enemyX + enemyVx * arrivalTicks. spawnBullet calculates arrivalTicks = ceil(distance / bulletSpeed). **Files:** - `vapourbot_garage/src/vapourbot/gun.nim` - stepBullets signature, interpolation logic, spawnBullet arrival calculation

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Reference: SirStone/SirRoboGarage#122