Summary of 3GPP Change Request S4-260088

Document Information

• Source: Samsung Electronics Co., Ltd.
• Title: pCR on 3D tiles, LOD and 3DGS delivery format requirements
• Specification: 3GPP TR 26.958 v0.1.1 (FS_3DGS_MED)
• Purpose: Agreement on text additions and modifications

Overview

This change request proposes comprehensive updates to TR 26.958 to address 3D Gaussian Splatting (3DGS) encapsulation and delivery format requirements, with particular focus on spatial random access and level of detail (LOD) mechanisms. The document introduces three main changes to improve clarity and technical accuracy.

Main Technical Contributions

1. Terminology Updates (1st Change)

New and Modified Definitions

• 3DGS tile (new definition): A spatial volume of the scene represented by a specific bounding volume, containing a set of 3D Gaussians for a given level of detail (LOD)

• Levels of detail (new definition): Multiple representations of a scene, each with a different set of data which represents different qualities of the scene for a compromise between visual detail and data size

• 3D tile (modified/removed): The previous generic definition ("discrete spatial partition of a massive geospatial dataset") is replaced with the more specific "3DGS tile" definition to better align with 3DGS-specific requirements

Rationale: The original TR lacked an LOD definition and used a non-3DGS-specific definition for 3D tiles. The new terminology better reflects the technical requirements for 3DGS delivery.

2. Use Case Description Refinements (2nd Change)

Updates to Clause 5.3 - Exploration of Large 3DGS Environment

Terminology Harmonization:
- Replaces generic "3D tiles" references with "3D Gaussians" in use case descriptions
- Updates "3D tiles" to "3DGS tiles" in working assumptions with reference to new technical clause
- Maintains LOD terminology as it is widely understood in 3D graphics

Key Technical Aspects:
- Adaptive delivery of 3D Gaussians at various LODs based on user pose and device capabilities
- Selection process maintains constant number of displayed splats for quality consistency
- Interactive delivery mechanism for 3D Gaussian sets at various detail levels
- Constrained navigation within captured regions

Working Assumptions Updates

Compression and Packaging:
- 3DGS tiles with different LODs serialized into delivery format
- Signaling for spatial and LOD indices and dependencies
- Editor's notes identify need for:
- Workflow documentation for different uplink/downlink traffic profiles
- Characterization of Gaussian parameters requiring signaling
- Evaluation of existing 3GPP media delivery frameworks

Transport and Delivery:
- Interactive delivery with predictive prefetch
- Edge-assisted content hosting for latency control
- Buffering strategies to minimize latencies and visual artifacts

Decoding and Rendering:
- UE parses 3DGS tile indices and manages GPU residency
- Real-time splat-based rendering with tile/LOD switching
- Navigation constraints based on capture information and collision detection
- Editor's note on expressing "allowed navigation volume"

3. New Clause on 3DGS Encapsulation and Delivery Formats (3rd Change)

This represents the major technical contribution, introducing a comprehensive new clause (Clause X) covering:

X.1 Introduction

Core Concepts:
- 3DGS scalability requires support for:
1. Position-based random access of 3D Gaussians
2. Delivery/rendering of different LODs

Technical Relationship:
- Spatial random access and LOD are non-orthogonal (same spatial volume can have different Gaussian sets for different LODs)
- Viewing frustum (derived from user pose) determines required spatial volumes and LODs
- Frustum includes: position, orientation, horizontal/vertical FoV, viewing distance
- Mechanisms relevant to both rendering efficiency and delivery optimization

X.2 Requirements

Two Primary Requirements Identified:

1. 3D Gaussian Set Identification: Method to identify 3DGS data into sets enabling association of 3D Gaussians at different LODs with spatial volumes

2. Frustum-Based Access: Method to identify and access required 3D Gaussians at different LODs using user's frustum for efficient delivery, access, and rendering

X.3 3DGS Tiles

Technical Definition:
- Method to associate spatial volumes with 3D Gaussians through 3DGS tiles
- 3DGS tile = spatial volume with specific bounding volume + set of 3D Gaussians for given LOD

Editor's Note: Indicates need for additional technical details

X.4 Related Compression Aspects

Compression Technology Requirements:

1. LOD and Partial Delivery Support: Ability to support LOD and partial spatial data delivery without compression optimization dependency

2. Optimized Compression: Real-time compression of 3DGS data optimized for LOD support and partial spatial delivery

Technical Impact

The changes establish a structured framework for:
- Standardized terminology for 3DGS spatial organization
- Clear requirements for encapsulation and delivery formats
- Foundation for future work on compression, signaling, and delivery protocols
- Alignment with interactive 6DoF streaming requirements from TR 26.928

The proposal moves from use-case-embedded technical concepts to a dedicated technical clause, providing clearer separation of concerns and enabling more detailed specification development.