Vetra

Every shot lands where physics says it should.

Vetra is an analytic-trajectory projectile simulation module for Roblox. Where most weapon systems move bullets by nudging position += velocity * dt each frame, drifting, tunnelling, disagreeing between client and server, Vetra uses the exact kinematic formula P(t) = Origin + V₀t + ½At². No drift. No frame-rate dependency. A shared ground truth.

Features

Analytic trajectory, exact position at any time, independent of frame rate
High-fidelity sub-segment raycasting, no bullet tunnels through thin geometry
Pierce, multi-surface penetration with momentum modeling and exit-point detection
Bounce, restitution, per-material coefficients, normal perturbation, corner-trap detection
Drag, linear, quadratic, or G-series empirical models (G1, G5, G6, G7, G8, GL, Custom)
Magnus effect, lateral force on spinning projectiles
Gyroscopic drift, long-range directional yaw from spin precession
6DOF aerodynamics, lift, pitching moment, pitch/yaw damping, roll damping, gyroscopic precession
Coriolis deflection, configurable per map, latitude-accurate with exaggeration scale
Tumble, destabilisation on speed loss or pierce, chaotic drag multiplier
Fragmentation, cone-distributed child bullets on pierce
Hitscan, single-frame hit resolution that skips kinematics; full pierce, bounce, and signal support with no per-frame cost
Homing, frame-by-frame steering with strength, duration, and acquisition radius
Trajectory provider, replace kinematics with any custom position curve
Supersonic / subsonic profiles, different drag, restitution, and scatter per speed regime
LOD and spatial partitioning, HOT / WARM / COLD tiers, interest-point driven
Parallel physics, distributes raycasts across Roblox Actors; ~flat 4–10ms up to 20,000 bullets
VetraNet, full networking middleware: serialization, rate limiting, origin validation, trajectory reconstruction, cosmetic replication, drift correction, all over one RemoteEvent
Typed builder, BehaviorBuilder with build-time validation and frozen output
MIT licensed

Installation

Get Vetra from the Roblox Creator Store:

→ Install Vetra on Roblox

Then drop the Vetra folder into ReplicatedStorage and require it from your weapon scripts.

local Vetra = require(game.ReplicatedStorage.Vetra)

Quick Start

local Vetra         = require(ReplicatedStorage.Vetra)
local BulletContext = Vetra.BulletContext

local Solver  = Vetra.new()
local Signals = Solver:GetSignals()

Signals.OnHit:Connect(function(context, result, velocity)
    if result then
        print("Hit", result.Instance.Name)
    end
end)

local Behavior = Vetra.BehaviorBuilder.Sniper():Build()

local context = BulletContext.new({
    Origin    = muzzlePosition,
    Direction = direction,
    Speed     = 900,
})

Solver:Fire(context, Behavior)

Performance

Parallel solver frame times measured on a live Roblox server, 120-frame samples:

Active bullets	Serial	Parallel	Speedup
50	10.3 ms	4.2 ms	2.5x
200	14.0 ms	4.2 ms	3.4x
1,000	45.2 ms	4.2 ms	10.8x
5,000	174.7 ms	5.5 ms	32x
20,000	-	10.3 ms	-

The parallel solver's frame time is essentially flat from 25 to 2,000 bullets. See the Benchmarks page for full data across all four profiles.

Documentation

Full documentation at vel136.github.io/Vetra

Features

Installation

Quick Start

Performance

Documentation

Community

License