Limitations

Honest list of what does not work yet, and why.

Bedrock features with no Java counterpart

The resource-pack side reads real Bedrock files, but a few things only exist in Bedrock:

• Materials are not Bedrock's shader materials. A material name only picks how a layer is drawn: translucent if it contains alphablend, translucent or blend, full-bright if it contains emissive, cutout otherwise.
• Particle effects play a Java particle with no options, or one of a handful of Bedrock built-ins mapped to their Java equivalents. Bedrock particle effect files are not read.
• Entity references (->) parse but give 0, and query.is_first_person is always 0.

clientTrackingRange and updateInterval cannot be data-driven

They are EntityType properties, frozen at registration, and there is one shared type. The generic type uses a tracking range of 12 chunks, generous enough for large species.

Natural spawning is not data-driven

spawn.biomes controls where a species' fossils generate, not where live creatures spawn. Creatures come from the fossil → DNA → embryo → egg chain. There is no natural spawn weight or spawn rule in the species format.

Flying has no aerodynamic simulation

entity_category: "flying" gives real flight navigation, hovering movement control and no fall damage, plus the fly and circle_target components. The fly component supports configurable minimum and maximum altitude, wander range and vertical range. Animation controllers can distinguish grounded and airborne states, so Pteranodon folds its wings while perched and switches between powered flight and a gliding pose.

This is still path-based flight rather than an aerodynamic simulation: lift, stalls, wind and momentum are not modelled, and landing is not a separate navigation phase.

Legacy entity ids linger

ancientcreature:triceratops, :tyrannosaurus_rex and :megalodon remain registered so existing worlds keep their creatures. They are data-driven now and nothing spawns them, but the registrations cannot be removed without deleting those creatures from old worlds. See Migration.

Creative tab and JEI before joining a world

The client only learns which species exist when it joins a server, so a listing built before that shows none. Both are rebuilt on join, so this is not visible in normal play.

Not verified in-game by automated tests

Automated tests cover the JSON formats, the codecs, the geometry baker, animation sampling, Molang, the behaviour registry, genetics and every shipped species file. They do not launch Minecraft. Anything involving actual rendering, pathing or gameplay needs the manual pass in Testing a species.