# Summary of 3GPP Change Request S4-260147

## Document Information
- **Source:** Pengcheng Laboratory, China Mobile Com. Corporation
- **Title:** [FS_3DGS_MED] Pseudo-CR on Enhanced Scenario for Avatar Communication Use Case
- **Specification:** 3GPP Draft TR 26.958 v0.1.1
- **Meeting:** TSG-SA4 Meeting #135, 9-13 February 2026, Goa, India

## Main Objective

This contribution proposes an enhanced scenario for avatar-based communication that combines parametric human models with 3D Gaussian Splatting (3DGS) technology. The proposal aims to enable efficient real-time interactive communication by transmitting compact motion parameters to drive a deformable mesh while using 3DGS for high-fidelity appearance rendering.

## Technical Contributions

### Enhanced Avatar Communication Architecture

The proposal introduces a hybrid representation approach consisting of:

- **Deformable mesh representation** driven by parametric human model parameters (e.g., SMPL-X for body/hands, FLAME for face)
- **3D Gaussian Splat representation** for appearance enhancement and fine detail capture
- **Separation of geometry and appearance** to optimize transmission efficiency

### Technical Processing Pipeline

#### Sender Side Processing

- **Capture:** User captured using one or more cameras
- **Parameter Extraction:** Geometric and animation parameters extracted using parametric models
  - SMPL-X for body and hand motion
  - FLAME for facial geometry and expression
- **Representation Generation:**
  - Deformable human mesh reconstruction based on extracted parameters
  - 3D Gaussian Splat generation for appearance details (fine surface detail, hair, clothing)
- **Spatial Alignment:** 3DGS representation aligned with deformable mesh

#### Transmission Strategy

- **Base Avatar:** Transmitted once at session setup or updated occasionally
  - Rigged mesh with skeletal structure and blendshapes
  - Static 3DGS representation
- **Animation Stream:** Time-varying model parameters transmitted during session
  - Compact parametric representation
  - Low-latency transmission for interactive communication
- **Update Frequency:** 3DGS updated at lower frequency than animation parameters

#### Receiver Side Processing

- **Animation Application:** Received parameters drive avatar motion
- **Deformation Propagation:** 3DGS follows mesh deformation
- **Rendering:** Composite approach combining:
  - Mesh-based shading
  - 3DGS-based appearance contributions
- **Viewpoint Adaptation:** Supported within application-defined constraints

### Working Assumptions

The proposal defines several key working assumptions:

**Capture and Animation Extraction:**
- Real-time capture using one or more cameras
- Real-time derivation of animation parameters from captured signals

**Representation:**
- Deformable mesh with associated rig
- Associated 3DGS for appearance rendering
- Static or low-frequency updated 3DGS representation

**Transmission:**
- One-time or occasional base avatar transmission
- Continuous time-varying animation parameter transmission
- Low-latency requirement for interactive communication

**Decoding and Rendering:**
- Animation parameter application at receiver
- Combined mesh and 3DGS rendering
- Constrained viewpoint adaptation support

## Key Innovation

The main technical innovation is the separation of geometric animation (transmitted as compact parametric data) from appearance representation (using 3DGS), enabling photorealistic real-time avatar communication with efficient bandwidth utilization suitable for bidirectional interactive applications.