FmmAttachableGenerator

Generates Bedrock attachable definitions for FMM bone models, mirroring Rainbow's BedrockAttachableContext geometry path 1:1. Emits: - materials.default = entity_emissive_alpha (stock Bedrock material, alpha cutout + alpha-proportional emissive). Opaque pixels still sample world light, so models render dark when the entity origin lands inside a solid block — see "Known limitation: Bedrock dark-in-shadow" below for the full story. - animations.first_person / third_person / head referencing the three animations produced by FmmAnimationGenerator. - scripts.animate with three context-conditional entries (no pre_animation indirection; matches BedrockAttachableContext.java:68-75).

Known limitation: Bedrock dark-in-shadow

Bedrock samples world-light at the entity origin (unlike Java, which samples at rendered geometry). FMM's packet armor stands often sit with their origin ~1.438 blocks below the visible model — frequently inside the ground — so world_light reads 0 and the bone renders pitch black on Bedrock clients.

Three fixes were attempted and rejected in May 2026:

1. Custom .material file (rspm_unlit:entity_emissive_alpha with USE_ONLY_EMISSIVE). Bedrock 1.16.100+ broke material inheritance from vanilla materials; the client emits a flood of content-log errors and the pack fails to load.
2. Per-viewer entity Y-lift (FMM-side) + pack-side compensation (geometry pivot offset OR head-animation translation). Both pack-side compensations create an offset between the cube and its rotation centre (the armor stand head bone pivot), so head_pose rotations swing the bone in an arc instead of rotating it in place. Geometrically impossible to fix without abandoning either lighting or rotation.
3. Material swap to entity_emissive (alpha = emissive intensity, .tga texture). Gives fullbright but eliminates the alpha channel needed for transparency. entity_emissive_layer would give both but isn't valid for attachables (not in the attachable schema).

There is no vanilla-supported Bedrock material that provides both transparency AND opaque-pixel-fullbright for attachables. The limitation is accepted: place FMM models in well-lit areas, or accept dark rendering when the entity origin is buried.