Generate deterministic projection tiles and guard-band chunks

[zoeyrose]

Important

This preserved world-imagery design now belongs to the fresh MIT shared renderer. Authored geography, labels, and content decisions remain in atrinik/content; rendering/projection code is shared by client, editor, and offscreen products.

Replacement implementation contract

Implement deterministic chunk coverage, guard bands, overlap/crop, naming/manifests, seam validation, batching, caching, and atomic image products through the shared wgpu/offscreen renderer. Preserve all geography/disclosure/product decisions while removing extracted classic-client assumptions.

Use explicit versioned scene/resource/projection inputs, deterministic clocks/profiles, bounded concurrency and memory, atomic outputs, manifests/digests, semantic-mask validation, and renderer metrics. No source-tree/runtime discovery or separate imagery renderer is permitted.

Verified original past work by an approved MIT provenance grantor may be copied, migrated, translated, or relicensed only through the merged complete-provenance grant directive.

Lighting-profile chunk invariants

Render and validate fully-lit and intended-darkness as separate canonical outputs over one projection/tile matrix. The explicit authoritative light field/profile is part of every chunk dependency and cache key; a chunk from one mode can never satisfy the other merely because content coordinates match.

Compute light guard bands from the actual influence/interpolation bounds for each profile. Monolithic-versus-chunked equality and cross-map/cross-depth seam tests run independently in both modes, including indoor/outdoor boundaries and static colored/negative emitters spanning a crop edge. A paired batch may reuse immutable scene geometry/resources and parallel CPU preparation/encoding, but keeps mode-specific light targets/readbacks/cache state isolated and commits results in deterministic order.

Both modes use the normal shared rendering/light/material path defined by #14. fully-lit supplies maximum neutral authoritative samples; it is not a special bypass shader or postprocess. Report the incremental GPU/CPU/readback/cache/storage cost of the second mode, apply bounded backpressure, and fail the whole revision if either matched pyramid is incomplete or mismatched.

Preserved product/design specification and historical implementation notes

Parent and roadmap

• Parent tracker: Generate world and region imagery through the shared renderer #13
• Roadmap: Roadmap: replace classic Atrinik with a fresh MIT Go and Rust stack atrinik#168
• Roadmap milestone: M3
• Prerequisites: Implement deterministic scene contexts and headless rendering #12, Define transactional ordered scene snapshots and revisioned deltas protocol#5, Implement bounded ordered scene snapshots and cross-depth rendering #11

Outcome

Compose complete regions from ordered scene snapshots using one isometric world projection and seam-free bounded chunks.

Scope

• Traverse horizontal tiled topology and linked physical depths into stable world coordinates.
• Compute conservative projected bounds from actual render commands/resources, including tall, doubled, rotated, stretched, multipart, and effect sprites.
• Render chunks with required scene/light guard bands, crop after rendering, and preserve one cross-map/cross-depth painter order.
• Emit raw RGBA and a versioned projection manifest mapping logical map/tile/depth coordinates to image anchors/polygons, labels, void coverage, hashes, and profile identities.

Superseded path / cleanup target

Do not composite complete maps/depths independently or keep scalar pixel_size metadata as a second coordinate model after consumers migrate.

Acceptance criteria

• Chunked output matches monolithic fixtures without clipping, duplicates, lighting discontinuities, or painter seams.
• Repeated runs with identical inputs/backend/profile produce identical manifests and hashes.
• Projection metadata covers every map/depth/tile and remains bounded for large worlds.
• Inconsistent topology or partial generation fails before publication.

Validation baseline

Before: world images place simplified per-map rectangles and cannot represent client isometric overlap or depth.

After: a deterministic projection/chunk pipeline produces raw client-rendered world imagery and exact coordinate metadata.

Run monolithic-versus-chunk comparisons, repeatability hashes, topology error fixtures, multi-depth/tall-sprite visual tests, and performance bounds.

This issue is a bounded child of #13. The parent remains open until every sibling child is complete.