GetAttributeDataArrayForAllPoints: non-float attributes have no conversion or mapping fallback

cpp/draco-helpers.h で GetAttributeDataArrayForAllPointsHelper と GetAttributeFloatArrayForAllPoints を比較することから始め、次に Uint8 JOINTS_0 を使用する Draco 圧縮済みのスキニングされた glTF で失敗を再現してください。完了条件は、型付き抽出が変換と非恒等マッピングをサポートし、不一致時に false を返さないことです。さらに、README の例で outSize をバイト数として説明すべきかどうかも確認してください。

Environment

@callstack/react-native-draco 0.3.0
three's GLTFLoader, RN 0.86, new architecture, iOS

Description

cpp/draco-helpers.h has two extraction paths that behave differently:

• GetAttributeFloatArrayForAllPoints (float requests) walks mapped_index and falls back to pa.ConvertValue<float>() for non-float source data — it handles quantization and non-identity mapping.
• GetAttributeDataArrayForAllPointsHelper<T> (every non-float typed request) only succeeds when pa.data_type() == type and pa.is_mapping_identity() — a direct memcpy. Any type mismatch or non-identity mapping returns false and decode fails. No ConvertValue fallback like Draco's Emscripten wrapper.

So Float32 POSITION/NORMAL/TEXCOORD works, but skinned meshes don't: JOINTS_0 is Uint8/Uint16 and WEIGHTS_0 is often quantized, so GLTFLoader requests typed arrays the helper refuses.

Minor: the outSize arguments are byte lengths (the helper asserts num * components * sizeof(T) == out_size); the README examples read like element counts.

Suggested fix: give the typed path the same ConvertValue-based extraction and non-identity mapping support the float path already has. Happy to send a PR.

Reproducible Demo

Load any Draco-compressed skinned glTF (JOINTS_0 stored as Uint8) through three's GLTFLoader wired to this module. Static meshes decode; the skinned mesh errors on attribute extraction, because GetAttributeDataArrayForAllPointsHelper<uint8_t> returns false unless the stored type and mapping match exactly.

Transparency note: this issue was drafted with AI assistance. I'm a human, I've personally verified the behavior in the source, and I'm happy to answer any questions or concerns directly. Thanks for the library.