I3S / Scene Layer Package
Jun 24,2026

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Introduction

I3S, which stands for Indexed 3D Scene Layer, is an open 3D geospatial data standard led by Esri and adopted by the OGC (Open Geospatial Consortium). Its accompanying format, the Scene Layer Package (SLPK), packages all scene layer resources into a single archive file. Built on modern web technologies such as JSON and REST, it is adapted to cloud, web, and mobile environments, supporting efficient streaming, storage, and visualization of large-scale heterogeneous 3D data. It is compatible with multiple types of 3D content including 3D objects, oblique photogrammetry, point clouds, and BIM. It is now widely supported by major GIS software such as ArcGIS and ContextCapture.

File Structure

The core implementation format of I3S, SLPK, is essentially a ZIP archive using the "store-only" compression mode. Internal files are mostly gzip-compressed except for textures, and the overall structure is organized as a tree-like node hierarchy. The core file structure can be divided into the following parts:

Global Description File: Centered around 3DSceneLayer.json, this file defines global metadata such as the scene's spatial extent, coordinate system, geometric rules, and LOD switching parameters. It serves as the entry configuration file for the entire SLPK.
Node Pages Directory (nodePages): Stores multiple JSON files that record tree structure information for all nodes in batch arrays, including node IDs, hierarchy levels, bounding volumes, and parent-child node indexes. This replaces the scattered index files of earlier versions, significantly improving I/O access efficiency.
Node Resources Directory (nodes): Divided into independent subfolders by node ID, this is the core data carrier of SLPK. It can be further subdivided into submodules including geometry data (geometries, typically binary files compressed with algorithms such as Draco), texture data (textures, supporting formats such as JPEG and KTX2), attribute data (attributes, storing corresponding field information in the field folder), and feature information (features, supported only for types such as 3D objects and BIM). Some versions also retain a shared shared resources folder and 3DNodeIndexDocument index files for backward compatibility.
Auxiliary Identification Files: Includes metadata files, @specialIndexFileHASH128@ checksum files, etc., used to record file verification information and extended attributes to ensure data integrity.

Pros

Open standards and strong compatibility: As an OGC-adopted open specification, it supports the vast majority of geospatial coordinate systems, including commonly used domestic systems such as CGCS2000. It can be seamlessly loaded across web, mobile, and desktop platforms and is natively supported by mainstream 3D software such as ArcGIS and ContextCapture.
High transmission and rendering efficiency: Using a pyramid LOD hierarchical and tiled structure, combined with multiple compression technologies such as gzip and Draco, it supports view-driven progressive streaming loading, significantly reducing transmission bandwidth and memory usage for large-volume 3D data, making it suitable for rapid scheduling of massive 3D scenes.
Comprehensive data carrying capacity: Natively supports multiple types of 3D data including 3D objects, oblique photogrammetry, point clouds, and BIM. It can independently store geometry, texture, and attribute data, and leverages RESTful interfaces for efficient querying and management of large volumes of non-geometric attributes, adapting to complex scenarios such as digital cities and GIS-BIM integration.
Convenient deployment and usage: SLPK packages all resources into a single zip-format file, eliminating the need to maintain scattered directory structures. It supports both offline local loading and direct publishing as cloud-based scene services, lowering the barriers to 3D data distribution and deployment.

Cons

Limited ecosystem openness: While the standard itself is open, the core loading and rendering logic relies on the ArcGIS JS API, and the related implementations are not fully open-source. Third-party engines outside the Esri ecosystem face relatively high adaptation costs.
Insufficient extensibility flexibility: The format design has some redundancy. The JSON description files have fixed fields without reserved custom extension space, making it difficult to quickly adapt to emerging 3D data characteristics and custom business requirements.
Complex version compatibility: Different versions of the specification have significant differences. For example, point cloud data from version 1.6 and earlier cannot be directly upgraded. Lower versions lack the nodePage mechanism, resulting in index loading performance that lags significantly behind higher versions, creating a high version adaptation threshold.
Weak local fine-editing capability: Compared to formats that natively support offline fine-grained modifications (such as OSGB), I3S/SLPK is more oriented toward online distribution and display. Operations such as local model repair and batch adjustment of attribute fields are less convenient.

Application Scenario

I3S applications cover full-scene 3D modeling and visualization in digital city construction. It can integrate real-scene data collected by drones and aerial photography, as well as urban building models, for smooth loading and display on web and mobile platforms. It also enables deep integration of GIS and BIM, supporting building lifecycle spatial analysis in the engineering and construction field. It can be used for efficient publishing and sharing of large-scale point cloud data. In scenarios such as surveying and mapping planning and disaster simulation, its streaming capability enables rapid scheduling of massive 3D data, supporting multi-platform collaborative spatial decision-making.