InstantHMR — model weights

A lightweight, ONNX-exportable distillation of facebook/sam-3d-body-dinov3 for 3D human pose estimation and mesh recovery: a RepViT-M1.5 backbone + a 9-token cross-attention decoder + CLIFF camera conditioning. Trained to mimic the SAM3D teacher's per-person 70-keypoint outputs from a single 224×224 crop.

Demo, training, and inference code live at the main InstantHMR repository: https://github.com/mohamdev/InstantHMR.

Files

File	Size	Purpose
instanthmr.onnx	~77 MB	fp16 ONNX export — what the demo and InstantHMR(...) wrapper load.
instanthmr.pth	~461 MB	PyTorch checkpoint for fine-tuning / further distillation.

Most users only need instanthmr.onnx. The .pth is included for people who want to continue training, swap the head, or re-export with different options — see docs/training.md in the main repo.

ONNX I/O

• Inputs
  • image — (N, 3, 224, 224) float32, ImageNet-normalised RGB.
  • cliff_cond — (N, 3) float32, [cx_norm, cy_norm, b_scale] of the detector bbox in the full frame (cx_norm, cy_norm ∈ [-1, 1], b_scale = max(bw, bh) / max(W, H)).
• Outputs
  • mhr_params — (N, 204) MHR pose + scale parameters.
  • shape_params — (N, 45) MHR identity blendshapes.
  • cam_trans — (N, 3) body translation in camera frame (metres).
  • joints_2d — (N, 70, 2) keypoints in normalised crop coords [-1, 1].
  • joints_3d — (N, 70, 3) body-centred 3D keypoints (metres, Y-down).

The 70 keypoints follow the MHR70 ordering — see instanthmr/skeleton.py for joint names and skeleton edges.

Quick start (ONNX)

Minimal end-to-end inference with onnxruntime, no extra dependencies:

import cv2
import numpy as np
import onnxruntime as ort

IMAGENET_MEAN = np.array([0.485, 0.456, 0.406], dtype=np.float32)
IMAGENET_STD  = np.array([0.229, 0.224, 0.225], dtype=np.float32)

# 1. Load the ONNX session (CUDA if available, otherwise CPU).
sess = ort.InferenceSession(
    "instanthmr.onnx",
    providers=["CUDAExecutionProvider", "CPUExecutionProvider"],
)

# 2. Load an RGB image and a person bbox [x1, y1, x2, y2].
image = cv2.cvtColor(cv2.imread("person.jpg"), cv2.COLOR_BGR2RGB)
H, W = image.shape[:2]
x1, y1, x2, y2 = 120, 40, 380, 600   # replace with your detector output

# 3. Square 1.2x crop around the bbox, resized to 224x224.
cx, cy = (x1 + x2) / 2, (y1 + y2) / 2
size = max(x2 - x1, y2 - y1) * 1.2
sx1, sy1 = int(cx - size / 2), int(cy - size / 2)
sx2, sy2 = int(cx + size / 2), int(cy + size / 2)
pad = [max(0, -sy1), max(0, sy2 - H), max(0, -sx1), max(0, sx2 - W)]
patch = image[max(0, sy1):min(H, sy2), max(0, sx1):min(W, sx2)]
patch = cv2.copyMakeBorder(patch, *pad, cv2.BORDER_CONSTANT, value=0)
crop  = cv2.resize(patch, (224, 224), interpolation=cv2.INTER_LINEAR)

# 4. Normalise + CHW.
img = (crop.astype(np.float32) / 255.0 - IMAGENET_MEAN) / IMAGENET_STD
img = np.transpose(img, (2, 0, 1))[None]   # (1, 3, 224, 224)

# 5. CLIFF conditioning vector (full-frame coords).
cliff = np.array([
    2.0 * cx / W - 1.0,
    2.0 * cy / H - 1.0,
    max(x2 - x1, y2 - y1) / max(W, H),
], dtype=np.float32)[None]                  # (1, 3)

# 6. Run the model.
mhr_params, shape_params, cam_trans, joints_2d, joints_3d = sess.run(
    None, {"image": img, "cliff_cond": cliff}
)

print(joints_3d.shape)   # (1, 70, 3) — body-centred metres, Y-down
print(joints_2d.shape)   # (1, 70, 2) — normalised crop coords [-1, 1]
print(mhr_params.shape)  # (1, 204)   — feed into Meta's MHR module for a mesh

For a full pipeline (RF-DETR person detector + InstantHMR + Rerun visualiser), use the PosePipeline helper from the main repository — pip install -r requirements.txt then python demo.py --image path/to/photo.jpg.

Body mesh

InstantHMR does not run the MHR mesh decoder — rendering the full mesh is resource-heavy and the default pipeline stays lightweight. The raw mhr_params and shape_params are exposed so you can feed them into Meta's MHR TorchScript module from the original SAM 3D Body release when you need vertices.

License

These weights are released under the SAM license, since InstantHMR is a distillation of facebook/sam-3d-body-dinov3. Refer to https://github.com/facebookresearch/sam-3d-body for the full license text and applicable use restrictions.

The accompanying source code in the InstantHMR repository is released separately under the Apache License 2.0.