# Endoskeletal

Venue: ICLR 2025 · Spotlight

Authors: Muhan Li, Lingji Kong, Sam Kriegman

A generative framework evolves 3D bodies with coupled soft tissue and rigid skeletons, a continuous morphology space, and one morphology-conditioned controller shared across bodies.

- [Paper](https://arxiv.org/abs/2412.01036): Generating Freeform Endoskeletal Robots
- [Code](https://github.com/phenoweave/endoskeletal)
- [Website](https://endoskeletal.github.io/)
- [Interactive page](https://www.beyond-infinity.top/research/endoskeletal/)

## Steps

### 1. SYNTHETIC SPACE OF BODIES

Before it can design a body, the model must learn what a body can be: it studies twenty million synthetic ones, branching skeletons wrapped in soft tissue.

- TRAINING SET: 20 MILLION

![Branching skeletons wrapped in soft tissue drift toward the viewer like stars, each lighting up as its skeleton grows.](https://www.beyond-infinity.top/agent/shots/endoskeletal_step1.jpg)

### 2. LATENT GENETIC CODES

Twenty million shapes are too many to search voxel by voxel, so each body is folded into a short genetic code where nearby codes make similar bodies.

- BODY: 262 144 VOXELS
- CODE: 512 NUMBERS

![Each body dissolves into its code, drawn as a twisting double helix, and the codes settle side by side across a wide floor.](https://www.beyond-infinity.top/agent/shots/endoskeletal_step2.jpg)

### 3. FROM GENOTYPE TO PHENOTYPE, FROM INDIVIDUAL TO POPULATION

A code is only numbers until a decoder grows it into a body of bone and soft tissue, with about two orders of magnitude more voxels than the earlier freeform robots. A generation of codes becomes a population.

- GRID: 64³
- ICRA 2024: 20 × 20 × 8

![Codes laid out on a square of tiles grow into bodies of bone and soft tissue, the centre one first under a sweeping sheet of light.](https://www.beyond-infinity.top/agent/shots/endoskeletal_step3.jpg)

### 4. SHARED BRAIN

No two of these bodies share a skeleton, so rather than train a brain for each, one shared brain reads any skeleton as a graph and drives every joint.

- BRAINS: 1
- SKELETONS: ANY

![Lines rise from every body on the tiles to one shared stack of network layers, and a signal runs up through the layers and back down to the bodies.](https://www.beyond-infinity.top/agent/shots/endoskeletal_step4.jpg)

### 5. EVOLUTION

Now that every body can move, each is tested in its own world; those that walk farthest steer the next generation of codes, and the loop begins again.

- SIM t: 6.00 s

![Each tile becomes a small simulated world where its body walks, and the worlds then merge into the centre one, where the fittest body stays.](https://www.beyond-infinity.top/agent/shots/endoskeletal_step5.jpg)