Background: Why Precision Fails in Large Leadwerks Worlds

IEEE-754 at Scale

Leadwerks relies on 32-bit floats for most world transforms and physics calculations. Floats offer ~7 decimal digits of precision, which is ample near the world origin but degrades with magnitude. At positions in the tens or hundreds of thousands of world units, tiny changes in position or rotation round away, creating visible jitter, collider overlap, and camera shimmer. What begins as sub-pixel error grows into perceivable artifacts as the scene's extents increase.

Game Engine Stack Interactions

Precision issues rarely arise in isolation. They interact with:

• Physics stepping: If physics integrates at a different cadence than rendering, error compounds during interpolation.
• Animation skinning: Skeletal matrices accumulate rounding; at scale, bones vibrate against colliders.
• Camera projection: A narrow near plane or large far plane exacerbates z-fighting and depth buffer quantization.
• Streaming systems: Terrain and static meshes streamed in/out at high coordinates can shift origin bias frame-to-frame.

Symptom Catalog and Their Architectural Signals

1) Physics Jitter and Interpenetration

Rigidbodies at rest visually "buzz"; vehicles slide on flat ground; fast movers tunnel through thin geometry. These indicate loss of sub-unit accuracy, broadphase instability, or time-step drift.

2) Camera Shimmy and Micro-Stutter

Even at stable FPS, the camera appears to vibrate when looking at distant geometry. This reflects model-view precision loss and depth buffer limitations compounded by a far origin.

3) AI Path Drift

Agents veer off navmesh or miss corners in distant tiles. The navmesh itself is fine; coordinate precision during path following and steering is not.

4) Z-Fighting, Shadow Acne, and Light Leaks

Decals and coplanar surfaces flicker; shadow maps show acne or peter-panning. This is often a near/far plane configuration problem amplified by large world coordinates and light frusta spanning huge volumes.

Leadwerks Architecture Relevant to Precision

Transforms and Scene Graph

Leadwerks' entity transforms are float-based. The scene graph composes parent-child transforms each frame. A deeply nested hierarchy magnifies precision loss because each local transform is multiplied into large world-space matrices.

Physics Integration

Leadwerks integrates physics via a fixed or semi-fixed step (commonly 60 Hz) while rendering may tick variably. If the two loops are not decoupled with interpolation, variable delta times can introduce inconsistent contact resolution, especially when colliders operate at coordinates with low mantissa precision.

Camera and Depth Buffer

Most pipelines use a 24-bit depth buffer. The distribution of depth precision is non-linear and concentrated near the camera's near plane. Excessive far planes (e.g., 50,000 units) or minuscule near planes (e.g., 0.01) obliterate mid-range depth precision, multiplying z artifacts in expansive terrains.

Diagnostics: Proving It's Precision, Not Performance

1) Origin Distance Telemetry

Instrument the player's world-space distance from <0,0,0>. Correlate artifact severity to radius thresholds (e.g., 10k, 25k, 50k units). A monotonic increase in jitter beyond a radius confirms precision involvement.

2) Forced Origin Reset A/B Test

Teleport the entire scene so the player returns close to the origin while preserving relative offsets; if artifacts vanish instantly, precision is root cause. Be sure to rebase both physics and render transforms in the same frame to avoid desync.

3) Time-Step Stability Audit

Log render delta, physics delta, and accumulator drift under load. If physics steps vary or accumulate error, contact solvers will exhibit unstable stacks that resemble precision bugs.

4) Depth Precision Probe

Render a diagnostic overlay that shows the camera near/far and estimated depth precision per meter at various ranges. If flicker worsens with wider depth ranges independent of object complexity, tune camera planes.

5) Hierarchy Amplification Test

Flatten a complex prefab hierarchy at runtime and compare jitter. If flattening reduces jitter, compounded matrix multiplications are contributing to precision loss.

Minimal Reproduction Scenarios

Scenario A: Distant Vehicle Jitter

Spawn a rigidbody vehicle at 40,000 units along X. Drive forward on a perfectly flat collider. Even at stable FPS, you'll see micro-oscillation in suspension and wheel-ground contact. Move the same vehicle to the origin—jitter largely disappears.

Scenario B: Z-Fight at Long Range

Two coplanar quads used for decals render fine near origin. At radius > 30,000 units with camera far plane set to 100,000 and near plane at 0.01, the decals flicker aggressively. Tightening near plane to 0.2 and far plane to 20,000 reduces flicker immediately.

Step-by-Step Fix: Floating Origin (World Rebase)

Concept

Keep the player and active gameplay area near world origin by periodically "rebasing" the scene: subtract a large offset from every entity and physics body so the player returns close to <0,0,0>. This preserves relative local positions and restores mantissa precision.

Rebase Trigger Strategy

• Threshold-based: When the player's origin distance exceeds, say, 8,192 units, schedule a rebase.
• Grid-based: Rebase whenever the player crosses N world tiles so streaming and nav chunks align to a stable grid.
• Safe-point based: Only rebase when physics velocities are below a threshold and no critical cinematics or network snapshots are mid-flight.

Implementation Notes

Rebasing must update:

• All scene entities and their children.
• Physics bodies and joints.
• Particle systems, decals, and projectiles.
• Navmesh origin or navigation waypoint caches.
• Audio listener and spatialized emitters (for Doppler correctness).
• Networked entity replication (apply inverse offset to remote clients if they use different origins).

Lua Example: Centralized Rebase Utility

-- Leadwerks Lua rebase utility
local Rebase = { threshold = 8192, offset = Vec3(0,0,0) }

local function rebaseVector(v, delta)
  return Vec3(v.x - delta.x, v.y - delta.y, v.z - delta.z)
end

function Rebase:MaybeRebase(player, worldEntities)
  local p = player:GetPosition(true) -- true = global space
  local dist2 = p.x*p.x + p.y*p.y + p.z*p.z
  if dist2 < self.threshold * self.threshold then return end
  local delta = Vec3(p.x, p.y, p.z)
  self.offset = self.offset + delta
  -- Freeze physics simulation for a frame
  Time:Pause()
  -- Shift all entities
  for _,e in ipairs(worldEntities) do
    local pos = e:GetPosition(true)
    e:SetPosition(rebaseVector(pos, delta), true)
  end
  -- Shift physics bodies explicitly if needed
  for _,e in ipairs(worldEntities) do
    local body = e:GetBody()
    if body then
      local bpos = body:GetPosition()
      body:SetPosition(rebaseVector(bpos, delta))
    end
  end
  -- Shift particles / custom systems as required
  Time:Resume()
end

return Rebase

C++ Example: Atomic World Shift

// Pseudocode for a safe, atomic rebase in C++
struct WorldRebaser {
  float threshold = 8192.0f;
  Vec3 totalOffset{0,0,0};
  void MaybeRebase(Entity* player, const std::vector<Entity*>& entities) {
    auto p = player->GetPosition(true);
    if (p.Length() < threshold) return;
    Vec3 delta = p; totalOffset += delta;
    Time::Pause();
    for (auto* e : entities) {
      Vec3 pos = e->GetPosition(true);
      e->SetPosition(pos - delta, true);
      if (auto* body = e->GetBody()) {
        body->SetPosition(body->GetPosition() - delta);
        body->SetLinearVelocity(body->GetLinearVelocity()); // force awake if needed
      }
    }
    // Adjust nav systems / audio emitters / decals here
    Time::Resume();
  }
};

Networking Considerations

Clients may rebase at different times. Avoid transmitting raw world coordinates. Instead:

• Send local coordinates relative to each client's current origin.
• Include origin epoch + offset vectors in replication headers.
• On receipt, transform into the receiver's local frame before interpolation.

Step-by-Step Fix: Deterministic Physics Stepping and Interpolation

Why It Matters

Even after rebasing, inconsistent time steps cause numerical noise that manifests as jitter. The fix is a fixed physics tick with render-side interpolation or extrapolation, ensuring stable contact resolution and predictable integration.

Accumulator Loop Pattern

// Pseudocode main loop
const float dt = 1.0f / 60.0f; // fixed physics step
float acc = 0.0f;
double last = Time::GetCurrent();
while (running) {
  double now = Time::GetCurrent();
  acc += float(now - last);
  last = now;
  while (acc >= dt) {
    World::UpdatePhysics(dt);
    acc -= dt;
  }
  float alpha = acc / dt; // for interpolation
  World::RenderInterpolated(alpha);
}

Entity Interpolation

Store previous and current transforms after each physics step; render interpolated transforms using . This reduces visible stutter when frame time fluctuates.

Bulletproofing Fast Movers

Enable continuous collision detection (CCD) on projectiles and vehicles, and cap maximum linear velocity per tick. With precision loss, CCD prevents tunneling that would otherwise appear only at distance.

Camera and Depth Buffer Stabilization

Tighten the Frustum

Set the near plane as large as visually acceptable (e.g., 0.1–0.2) and avoid astronomical far planes. Split views for map/photomode rather than a single "one size fits all" frustum.

Reverse-Z (If/When Available)

If your pipeline supports reverse-Z (far plane at 0, near at 1) with floating point depth, adopt it to push precision toward the far distance. If not available, prioritize frustum discipline and per-camera far plane limits.

Stable Matrices and Order of Operations

Build view-projection matrices close to the origin following rebase, and prefer world-space calculations that minimize large additive biases before multiplication.

Animation and Skinning at Scale

Single vs. Double Precision for Skinning

When authoring or importing, keep bone transforms as compact as possible and avoid deep parent chains. If extending native code, consider double-precision accumulation for skeleton root transforms near the origin, then cast to float for GPU submission.

Freeze Bones During Rebase

When rebasing, snapshot pose matrices, shift root transforms, then reconstruct skinning matrices in the same frame to avoid visible "bone pop".

AI Navigation and Path-Following Corrections

Navmesh Tiling with Local Space

Tile navmesh data and store tile-local coordinates. On rebase or tile swap, keep agent state in tile-local frames to avoid precision loss in steering calculations.

Path Smoothing With Clamped Epsilon

Use a distance epsilon proportional to world scale but capped so floating-origin transitions do not cause oscillation at corners. For example, epsilon = min(0.1 * agentRadius, 0.25).

Authoring and Units: Preventing Error at Source

Normalize Units

Pick a canonical unit (e.g., 1 unit = 1 meter). Ensure art, physics, and code use the same scale. Avoid tiny or massive scales that force physics tolerance changes or depth precision collapse.

Pivot Discipline

Place object pivots where local transforms are stable (e.g., base of characters, center of mass for vehicles). Large pivot offsets magnify rounding error when multiplied into world transforms.

Hierarchy Hygiene

Limit parent-child depth in frequently animated actors. Prefer flat hierarchies with explicit constraints rather than deep chains that accumulate error.

Common Pitfalls and How to Avoid Them

Pitfall 1: Rebasing Only the Visuals

Shifting meshes without updating physics bodies, joints, and triggers leads to invisible collisions and "ghost" forces. Always rebase both render and physics representations atomically.

Pitfall 2: Network Snapshots in Mixed Frames

Sending a snapshot mid-rebase yields mismatched frames on clients. Gate replication so snapshots are emitted only before or after the atomic shift, not during.

Pitfall 3: "Fixing" With Giant Near Plane

Cranking near plane too high may solve z-fighting but causes frustrating clipping of nearby geometry and first-person arms. Balance near/far planes with content needs.

Pitfall 4: Relaxed CCD and Thin Geometry

Turning off CCD or using wafer-thin colliders invites tunneling at distance. Use realistic thickness and enable CCD for high-speed actors.

Operational Playbook for Production Teams

Runbooks and Alerts

• Alert when origin distance exceeds your rebase threshold by 20% without a successful shift.
• Alert on physics step overruns (missed steps or accumulator drift > 2 frames).
• Log rebase events with counts of shifted entities and max velocity at shift time.

QA Test Plans

• Soak tests: 2–4 hours of traversal across maximum world radius while driving fast movers and firing projectiles.
• Camera stress: Rapid FOV changes and far-clip sweeps to expose depth instability.
• Network sync: Multi-client rebase under packet loss to validate per-client local frames.

Performance Budgets

Ensure your rebase operation runs in under a frame budget. If necessary, split static world into sectors and amortize shifting over several frames while freezing gameplay-critical systems.

Code Patterns and Utilities

1) Centralized Coordinate Service

Maintain a singleton that owns the current world offset and exposes conversion helpers, so every system uses the same reference.

// CoordinateService.h
struct CoordinateService {
  static CoordinateService& I();
  Vec3 worldOffset; // accumulated rebase offset
  Vec3 ToLocal(const Vec3& world) const { return world - worldOffset; }
  Vec3 ToWorld(const Vec3& local) const { return local + worldOffset; }
};

2) Interpolated Transform Component

// InterpTransform.lua
InterpTransform = { prev = Vec3(0,0,0), curr = Vec3(0,0,0) }
function InterpTransform:OnPhysicsStep(e)
  self.prev = self.curr
  self.curr = e:GetPosition(true)
end
function InterpTransform:GetRenderPosition(alpha)
  return self.prev + (self.curr - self.prev) * alpha
end

3) Safe Rebase Gate for Networking

// NetGate pseudocode
bool CanRebase() {
  return Net::OutstandingSnapshots() == 0 && Physics::MaxVelocity() <= 1.0f;
}
void TryRebase() {
  if (!CanRebase()) return;
  Broadcast(RebaseBegin{epoch++});
  DoAtomicRebase();
  Broadcast(RebaseEnd{epoch});
}

Case Study: Open-World Vehicle Combat

Problem

Vehicles jittered and occasionally fell through bridges after 30 minutes of play. QA could not reproduce in small maps.

Diagnosis

• Jitter correlated with distance from origin > 20k units.
• Physics and render loops shared a variable delta; under load, physics stepped inconsistently.
• Far plane set to 80,000; near plane 0.03.

Fixes Implemented

• Floating origin at 8,192 units with atomic physics/render rebase.
• Fixed 60 Hz physics with render interpolation.
• Near/far set to 0.15/25,000 and per-camera far plane overrides for snipers/photomode.
• Enabled CCD on fast vehicles and made bridge colliders thicker.

Outcome

Jitter eliminated; tunneling reduced to zero in 8-hour soak; shadow acne significantly reduced; networked play stable across client-specific rebase epochs.

Long-Term Best Practices

Design for Local Space First

Architect systems to operate in local coordinates. Treat world coordinates as presentation-layer concerns, transformed at boundaries (rendering, physics submission, replication IO).

Establish Precision SLAs

Define maximum world radius, minimum near plane, and maximum hierarchy depth for content. Bake these into CI validation tools that reject assets or camera rigs violating the contract.

Determinism Where It Counts

For competitive multiplayer, lock physics to a deterministic step and keep gameplay-critical logic in fixed update. Render may be fancy; gameplay must be repeatable.

Operational Observability

Expose origin distance, physics step drift, CCD toggles, and rebase counters to your telemetry dashboard. What you can't see will break in production.

Troubleshooting Checklist

Before You Ship

• ✅ Physics runs at fixed dt with interpolation.
• ✅ Camera near/far tuned per role; no universal 100k far plane.
• ✅ Floating origin implemented and tested with networking.
• ✅ CCD on fast movers; realistic collider thickness.
• ✅ Nav and AI operate in local-tile space.
• ✅ Asset scale unified; pivots and hierarchies validated.

When a Bug Report Arrives

• Reproduce at large origin distances; log radius and depth settings.
• Run the forced rebase A/B; if symptoms vanish, proceed with precision fixes.
• Audit time-step logs; ensure accumulator loop integrity.
• Inspect collider thickness and CCD flags on offenders.
• Check nested transform depth on jittery actors.

Conclusion

Precision-related defects in Leadwerks are not mere "engine quirks"; they are systemic architecture issues that emerge in expansive worlds and live operations. The combination of floating origin, deterministic physics stepping, disciplined camera frusta, and asset/unit hygiene resolves not only immediate symptoms—jitter, tunneling, z-fighting—but also builds a resilient foundation for future content. Treat world coordinates as a resource to be managed, not an infinite canvas, and your simulation will remain stable no matter how far players roam.

FAQs

1. Do I need floating origin if my maps are < 10 km?

Maybe not for casual traversal, but high-speed projectiles and precise animations can still expose precision loss at a few kilometers. Implement a simple rebase anyway; it is cheap insurance for expansions and DLC.

2. Won't rebasing break networking and replays?

Not if you transmit local-frame coordinates with epoch metadata and apply conversion on receipt. Record/replay systems should capture origin epochs alongside transforms to reconstruct the same local frames deterministically.

3. Can I fix jitter by switching to double precision everywhere?

Full double precision is rarely practical in a real-time engine due to memory and bandwidth costs. Use doubles only in select accumulation paths (e.g., camera root, skeletal root) and rely on floating origin to regain precision broadly.

4. How often should I rebase?

Base it on artifact onset and performance. Common thresholds are 4–12k units. Rebase during safe windows and throttle so it never collides with streaming spikes or snapshot emission.

5. Why does tightening the camera near plane help so much?

Depth precision clusters near the camera; a larger near plane drastically increases usable precision across mid and far distances. Combined with a sensible far plane, it reduces z-fighting and shadow acne even before other fixes.