Pose Driven 3D Characters

Stand in front of the camera and a rigged 3D character copies your pose in real time.

Model

Two models, no training:

• YOLO pose (models/yolo26s-pose.pt) returns 17 body keypoints per person (shoulders, elbows, wrists, hips, knees, ankles, face), tracked across frames and smoothed with a one euro filter.
• Rigged glTF characters (models/characters/*.glb) carry their own skeletons: Michelle (Mixamo), Rigged Figure and Cesium Man (Khronos samples). Switch with M / N. The .glb files are read directly - meshes, skinning weights, bones and embedded textures - and drawn by a small software rasterizer, so there is no game engine and no GPU requirement.

Logic

Each bone is aimed at the direction its keypoints describe. A bone points along parent.rotation @ child_offset, so making that equal the target gives its local rotation:

R = animated_parent.rotation^-1 @ swing(rest -> target) @ bind_parent.rotation

Both accumulated rotations are needed, animated and bind. Using the animated one on both sides only works when the bind rotation is identity, which is never true once a rig has an axis-conversion root, and it misaims every limb by up to 20 degrees.

The rest of it:

• Depth. One camera sees no depth, so a limb shorter than its own reference length must be angled toward or away from the lens; that missing length is recovered as a damped Z component.
• Turning. Shoulders narrower than the body's proportions mean the torso is turned. That yaw is folded into every bone's swing, because each driven bone's orientation is absolute - spinning one alone is undone by the next one down.
• Mirroring. The camera image is flipped, so left and right chains swap and the horizontal axis flips: raise your right arm and the character raises its right arm, facing you.
• Speed. All per-triangle work - projection, culling, lighting, colour - is batched in numpy, leaving one OpenCV polygon fill per triangle, and dense meshes are thinned at load to a triangle budget. Roughly 30-70 FPS depending on the character.

Views cycle with K: character only, character with a camera inset, or camera with a character inset. Keypoints and the skeleton are drawn on the camera image.

Keys: K view, M / N model, F detail, L keypoint names, Y / P rotate view, R reset view, D debug, H help, Q quit.

Run

pip install -r requirements.txt
python src/app.py

python src/app.py --model "Rigged Figure"
python src/app.py --camera 1 --pose-size 448 --no-mirror

by Salimli Ayzek (Салимли Айзек): https://mathematiclove.github.io