Open XR support

[Aggror]

Implement OpenXR for Stride. Similar to the other VR backends.

Previous work on this was halted unfortunately.

Discussion: #1848
Open Collective: https://opencollective.com/stride3d/projects/openxr-support

Feature Request: Implement OpenXR Support in Stride 3D

Summary
Adding OpenXR Support by integrating a robust version into Stride. OpenXR provides a unified API for VR/AR devices, making it a critical feature for modern immersive applications.

Objectives

1. Implementation Goals

   • Enable OpenXR support similar to existing VR backends.
   • Verify compatibility with VR headsets and mobile devices.
   • Ensure integration aligns with the current VR abstraction layer, requiring potential small adjustments.

2. Bare Minimum Functionalities

   • Basic head tracking and controller input.
   • Rendering compatibility for OpenXR-enabled devices.
   • Workflow adjustments to support OpenXR on mobile platforms.

3. Current Developer Issues

   • Lack of proper documentation and examples for using OpenXR with Stride 3D.
   • Vulkan support requires fixes for a seamless VR experience.
   • Developers report challenges with the VR abstraction layer's alignment with OpenXR requirements.

4. Testing and Platform Support

   • Test OpenXR implementation on popular VR headsets (e.g., Oculus, HTC Vive).
   • Test mobile compatibility for AR/VR applications.
   • Focus on Vulkan support (DX12 support deemed unnecessary for this phase).

5. Documentation Needs

   • Guides on using OpenXR for VR/AR workflows in Stride.
   • Examples for common use cases (headset setup, rendering adjustments, etc.).

Benefits

• Unified VR/AR Development: OpenXR eliminates the need for multiple SDKs, simplifying development for multiple VR platforms.
• Cross-Platform Compatibility: Mobile and headset support expands Stride 3D's utility for AR/VR developers.
• Future-Proofing: OpenXR is the standard for XR development, ensuring Stride 3D stays competitive in immersive tech.

Related Links

• OpenXR for Stride on OpenCollective
• GitHub Discussion: Implement OpenXR for Stride

Next Steps

1. Test and validate the OpenXR implementation on supported devices.
2. Fix Vulkan support issues to ensure compatibility.
3. Create detailed documentation and guides for developers.
4. Gather feedback from the community to prioritize additional improvements.

Open Collective Project
https://opencollective.com/stride3d/projects/openxr-support