LostBeard/SkinTokens-bf16

SkinTokens (TokenRig), bf16 safetensors for SpawnDev.ILGPU.ML

A format conversion of VAST-AI/SkinTokens (experiments/articulation_xl_quantization_256_token_4/grpo_1400.ckpt), the GRPO-refined TokenRig checkpoint, for the C# / ILGPU re-implementation in SpawnDev.ILGPU.ML (SpawnDev.ILGPU.ML.SkinTokens), which rigs a character mesh (skeleton and learned per-vertex skin weights) on the GPU, desktop or browser (WebGPU).

All credit for the model goes to the authors of SkinTokens / UniRig and VAST AI Research; the original work is MIT licensed and so is this conversion.

• Paper: SkinTokens: A Learned Compact Representation for Unified Autoregressive Rigging (arXiv:2602.04805)
• Original weights and code: https://huggingface.co/VAST-AI/SkinTokens , https://github.com/VAST-AI-Research/SkinTokens

What was changed

skintokens.safetensors (one file, 1.15 GB, 512 tensors, bf16) holds the inference tensors of the original checkpoint with these mechanical changes, nothing retrained:

• the checkpoint's bf16 tensors are stored unchanged; training-only tensors (the VAE's encoder and quantiser input side) are dropped;
• Qwen3 layers: q_proj, k_proj, v_proj fused into self_attn.qkv_proj (rows [q | k | v]), gate_proj and up_proj fused into mlp.gate_up_proj;
• the Michelangelo encoder's fused attention projections regrouped from [head][part][dim] rows to [part][head][dim];
• the VAE's attention (Tripo2 blocks interleave q, k, v per head): attn1.qkv.weight and attn2.kv.weight regrouped to [part][head][dim].

The conversion script is tools/unirig-harness/reference/export_weights.py skintokens in the SpawnDev.ILGPU.ML repository. The C# port is tested against the original PyTorch classes (same token sequence, skin weights to 5.7e-5 relative RMS with exact kernels).

Note for anyone loading this elsewhere: the original model keeps some non-persistent buffers (the VAE's frequency / phase tables and Qwen3's inv_freq) rounded to bf16 by .to(bfloat16); those are not stored here, they are recomputed (and must be rounded to bf16 to match the original).