Smooth nuke point-light position per frame in ambient mode

[evanpelle]

Summary

Follow-up to #4255. That PR made nuke sprites glide per render frame — UnitPass.drawMissiles lerps each nuke's lastPos→pos by wall-clock progress through the current tick. But in ambient/night mode the glow behind a nuke comes from a separate pass, PointLightPass, whose instance buffer is packed once per tick in updateLights() from the raw unit.pos. Its per-frame draw() (run every frame via LightmapPass) only set uniforms and issued the instanced draw — it never repositioned the lights. So the sprite moved at 60fps while its light jumped once per 100ms tick.

Fix

Mirror UnitPass's smoothing in PointLightPass:

• updateLights() records a smoothSegs tuple (lightIdx, lastX, lastY, x, y) for each SMOOTHED_NUKE_TYPES unit whose lastPos !== pos, and stamps lastUnitsUpdateMs.
• A new applySmoothing(), called at the top of draw(), lerps those lights by wall-clock tick progress ((now - lastUnitsUpdateMs) / tickIntervalMs, clamped to 1) and re-uploads only the affected instances. Unlike UnitPass (which re-uploads its tiny missile buffer wholesale), the light buffer can hold thousands of static structure lights, so a full per-frame re-upload would be wasteful.
• tickIntervalMs comes from a new config constructor param, wired through in Renderer.ts (the same config already passed to UnitPass).

The light now uses the exact same lastPos→pos endpoints and alpha as the sprite, so the two track together.

Test plan

• npx tsc --noEmit, eslint, and prettier all clean.
• npx vitest tests/client/render --run — 40 passed.

🤖 Generated with Claude Code

[coderabbitai]

Walkthrough

A new NukeSmoother utility class extracts position interpolation logic for reuse across rendering passes. Both UnitPass and PointLightPass are refactored to replace local smoothing state with this utility. UnitPass removes tuple-array buffering and timing state; PointLightPass adds Config dependency to initialize the smoother. Tests are updated to drive smoothing through the new NukeSmoother interface.

Changes

Nuke and light position smoothing refactoring

Layer / File(s)	Summary
NukeSmoother utility class src/client/render/gl/utils/NukeSmoothing.ts	Introduces NukeSmoother to record per-instance position segments (instanceIdx, lastX, lastY, x, y) during a tick and interpolate them on render using wall-clock elapsed time. Exposes reset(), record(), isEmpty, and apply(set) for segment management and interpolation callback invocation.
UnitPass migration to NukeSmoother src/client/render/gl/passes/UnitPass.ts	Removes local SMOOTH_SEG_STRIDE constant and smoothing state fields (smoothSegs, lastUnitsUpdateMs, tickIntervalMs), replacing them with a single nukeSmoother field. Constructor initializes via config.msPerTick(), updateUnits() resets per tick, unit iteration records segments, and applyMissileSmoothing() applies interpolated positions via this.nukeSmoother.apply().
PointLightPass integration with NukeSmoother src/client/render/gl/passes/PointLightPass.ts, src/client/render/gl/Renderer.ts	Adds Config import and constructor parameter to PointLightPass, initializing nukeSmoother from config.msPerTick(). updateLights() resets the smoother and records segments for SMOOTHED_NUKE_TYPES units. New applySmoothing() method interpolates positions and re-uploads affected light instances via gl.bufferSubData; draw() calls it before the instanced draw. GPURenderer passes config at the PointLightPass call site.
Test harness updates tests/client/render/gl/UnitPassSmoothing.test.ts	makeSmoothingHarness imports NukeSmoother, stubs performance.now to control wall-clock progress, creates and resets a NukeSmoother, records segment tuples directly, and injects nukeSmoother plus missileCount into the UnitPass instance, replacing legacy field injection.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Possibly related PRs

• openfrontio/OpenFrontIO#4255: This PR refactors the missile position smoothing originally introduced in #4255 by extracting the flat tuple-based logic into a dedicated NukeSmoother utility class and applying the same pattern to PointLightPass light interpolation.

Poem

🚀 Smoothing logic breaks free from the pass,
A NukeSmoother handles the mass.
Both Unit and PointLight now delegate,
Position segments interpolate. ✨
Wall-clock progress drives the blend,
One utility, two passes—refactored end!

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly describes the main change: adding frame-by-frame smoothing for nuke point-light positions in ambient/night mode, which is the core objective of this PR.
Description check	✅ Passed	The description provides comprehensive context about the problem (desynchronization between sprite and light movement) and the solution (mirroring UnitPass smoothing in PointLightPass), directly relating to all changes in the changeset.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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Caution

Some comments are outside the diff and can’t be posted inline due to platform limitations.

⚠️ Outside diff range comments (1)

tests/client/render/gl/UnitPassSmoothing.test.ts (1)

34-74: 🛠️ Refactor suggestion | 🟠 Major | 🏗️ Heavy lift

Use setup() helper instead of manual UnitPass prototype wiring in tests.

This harness directly constructs UnitPass via Object.create(...) and custom field injection, which bypasses the required test setup path for tests/**/*.test.ts. Please migrate this harness to use tests/util/Setup.ts and drive smoothing through the simulation-oriented setup flow.

As per coding guidelines: “tests/**/*.test.ts: Use the setup() helper from tests/util/Setup.ts to create test game instances and exercise core simulation directly.”

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@tests/client/render/gl/UnitPassSmoothing.test.ts` around lines 34 - 74, The
makeSmoothingHarness function manually constructs a UnitPass instance using
Object.create(UnitPass.prototype) and Object.assign to inject properties, which
bypasses the required test setup path. Replace this manual prototype wiring with
a call to the setup() helper from tests/util/Setup.ts to create a properly
initialized test game instance. Update makeSmoothingHarness to use the
simulation-oriented setup flow, which will ensure the UnitPass is correctly
initialized through the standard testing infrastructure rather than bypassing it
with direct property injection.

Source: Coding guidelines

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Outside diff comments:
In `@tests/client/render/gl/UnitPassSmoothing.test.ts`:
- Around line 34-74: The makeSmoothingHarness function manually constructs a
UnitPass instance using Object.create(UnitPass.prototype) and Object.assign to
inject properties, which bypasses the required test setup path. Replace this
manual prototype wiring with a call to the setup() helper from
tests/util/Setup.ts to create a properly initialized test game instance. Update
makeSmoothingHarness to use the simulation-oriented setup flow, which will
ensure the UnitPass is correctly initialized through the standard testing
infrastructure rather than bypassing it with direct property injection.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: ab1f08d2-033f-417b-993d-ba26b0444a01

📥 Commits

Reviewing files that changed from the base of the PR and between af930dc and ebb1b08.

📒 Files selected for processing (4)

• src/client/render/gl/passes/PointLightPass.ts
• src/client/render/gl/passes/UnitPass.ts
• src/client/render/gl/utils/NukeSmoothing.ts
• tests/client/render/gl/UnitPassSmoothing.test.ts