A Review of the current capabilities of USD and glTF
Here we will review the capabilities of USD (Universal Scene Description) and glTF (GL Transmission Format) and make recommendations for cooperation between these formats. We need to consider their strengths, weaknesses, and typical use cases.
Overview of USD and glTF
USD (Universal Scene Description)
Developed by: Pixar
Strengths:
Flexibility and Scalability: Designed for complex scenes and large-scale productions. Supports hierarchical scene descriptions, multiple scene variants, and rich metadata.
Interoperability: Extensively used in VFX and animation pipelines. Supports a wide range of data types including geometry, shading, lighting, rigging, and animation.
Non-destructive Editing: Allows for layered, non-destructive edits which is beneficial in collaborative environments.
USDZ: A package format (USDZ) that is optimized for sharing and viewing on iOS devices.
Weaknesses:
Complexity: Can be overkill for simple use cases. Requires more computational resources and storage.
Steeper Learning Curve: More complex to learn and implement.
glTF (GL Transmission Format)
Developed by: Pixar
Strengths:
Flexibility and Scalability: Designed for complex scenes and large-scale productions. Supports hierarchical scene descriptions, multiple scene variants, and rich metadata.
Interoperability: Extensively used in VFX and animation pipelines. Supports a wide range of data types including geometry, shading, lighting, rigging, and animation.
Non-destructive Editing: Allows for layered, non-destructive edits which is beneficial in collaborative environments.
USDZ: A package format (USDZ) that is optimized for sharing and viewing on iOS devices.
Weaknesses:
Complexity: Can be overkill for simple use cases. Requires more computational resources and storage.
Steeper Learning Curve: More complex to learn and implement.
glTF (GL Transmission Format)
Developed by: Khronos Group
Strengths:
Efficiency: Optimized for real-time rendering applications, such as web and mobile. Focuses on compact file sizes and fast load times.
Ease of Use: Easier to learn and implement, especially for web developers and smaller projects.
PBR: Physically-Based Rendering (PBR) support, making it suitable for realistic materials and lighting.
Wide Adoption: Widely used in AR/VR, games, and web applications.
Weaknesses:
Limited Scope: Not designed for complex scene descriptions or large-scale production pipelines.
Less Flexibility: Less suitable for non-real-time applications and complex asset management.
Use Cases and Recommendations for Cooperation
Use Case 1: Real-Time Applications (AR/VR, Games, Web)
Strengths of glTF:
glTF's efficiency and ease of use make it ideal for real-time applications.
The small file size and quick load times enhance performance in web and mobile environments.
Recommendations:
Adopt glTF for real-time applications where quick load times and compact file sizes are crucial.
Bridge Tools: Develop tools that can convert USD assets to glTF for real-time use, ensuring that assets created in complex pipelines can be easily utilized in real-time applications.
Use Case 2: VFX and Animation Production
Strengths of USD:
USD's flexibility and non-destructive editing capabilities are ideal for large-scale, collaborative projects in VFX and animation.
Support for complex scene hierarchies and multiple scene variants enhances productivity.
Recommendations:
Adopt USD for VFX and animation pipelines to take advantage of its scalability and rich feature set.
Interoperability Tools: Create robust import/export tools between USD and glTF to ensure that assets can move seamlessly between production and real-time environments.
Use Case 3: Interactive Experiences on Mobile Devices
Strengths of Both Formats:
USDZ for iOS provides a good solution for sharing and viewing rich 3D content on Apple devices.
glTF is already optimized for web and mobile environments.
Recommendations:
Use USDZ for iOS: For sharing complex 3D assets on Apple devices, USDZ is preferable due to its native support.
Cross-Platform Tools: Develop conversion tools that ensure assets can be converted from USD/USDZ to glTF and vice versa, enhancing cross-platform compatibility.
Use Case 4: Collaborative Design and Review
Strengths of USD:
USD's support for non-destructive editing and rich metadata makes it ideal for collaborative environments.
Recommendations:
Adopt USD for design and review stages in collaborative projects.
Interchange Standards: Encourage the development of standards and best practices for interchanging data between USD and glTF to ensure seamless collaboration across different tools and platforms.
General Recommendations for Cooperation
Standardized Conversion Tools: Develop standardized tools and libraries for converting assets between USD and glTF, ensuring data integrity and fidelity.
Cross-Platform Interoperability: Promote initiatives that enhance cross-platform interoperability, allowing assets to move seamlessly between different ecosystems.
Community Collaboration: Encourage collaboration between the USD and glTF communities to share best practices, improve interoperability, and develop shared extensions where appropriate.
Education and Training: Provide resources and training to help developers and artists understand the strengths and appropriate use cases for each format, promoting informed decision-making.
By leveraging the strengths of both USD and glTF, and fostering cooperation between these formats, it is possible to create a more cohesive and efficient ecosystem for 3D content creation and consumption.
