File formats

Native project format — .pvp

Projects are ZIP containers (.pvp) holding project.json plus embedded texture PNGs. Save/open are downloadable; open validation replaces nothing on failure — invalid transactions and replacements are rejected without changing the current project.

• IndexedDB autosave runs with protected pending recovery: inspectAutosave atomically reserves the durable pending copy and returns empty/valid/invalid with raw backup text, and resolveRecovery resolves only that protected copy while preserving newer current records.
• Recovery is optional and is not a substitute for downloadable backups.
• V1 project files reject future versions; automatic version migrations are not yet needed or implemented.

Size & integrity caps

Cap	Limit
Static PNG input	32 MiB, 16384 px/dimension, 16,777,216 px total; APNG rejected explicitly
Projects — aggregate PNG bytes	64 MiB
Projects — PNG pixels	33,554,432
Scanline output	192 MiB
JSON manifests	24 MiB
Project container	96 MB compressed / 128 MB decompressed
Undo snapshots	64, O(document size)
Object hierarchy	128 ancestor edges
UV range	0..1 with 1e-6 drift tolerance

Every atlas must match actual validated IHDR dimensions; malformed chunks/CRCs/streams are rejected consistently. The shared bounded PNG CRC/zlib/scanline validation applies across import, projects, recovery and export. Atlas IDs must be ZIP-safe (up to 128 characters). Details in PNG_VALIDATION.md.

Exports

Export	Contents
GLB	Self-contained textured GLB. In-browser export detects fractional alpha and uses BLEND; cutouts use MASK. Headless exports use the documented MASK default unless a probe is supplied.
OBJ bundle	ZIP with OBJ + MTL + texture PNGs. OBJ transparency depends on the importing application's MTL/PNG support.

Exports are independently tested through standard Three.js loaders. Export hierarchy is flattened; exports never change the source document.

Not supported

• Painting, linked prefabs/instances, animation/timelines, rigging, advanced mesh cuts, imported third-party models, FBX/DAE and movie rendering are not implemented.
• Third-party native file formats are not supported.