OpenXR

This page covers how to integrate OpenXR standards into your metadata through namespaces.

Overview and Use Cases

OpenXR is an open, royalty-free standard for accessing virtual reality (VR) and augmented reality (AR) platforms and devices. It provides a common foundation for VR and AR applications to run across various hardware platforms.

Common use cases include:

XR application compatibility metadata
Hardware requirements specification
Device capability descriptions
Input binding configurations
XR content accessibility information
Immersive experience parameters

Core Properties and Extensions

OpenXR provides a standardized way to interact with XR hardware:

Core Components: Runtime, Application, Session, Action, Space
Key Concepts:
- Instance: The entry point to the OpenXR runtime
- Session: The connection between an application and a user's physical environment
- Action: An input or output operation that an application exposes
- Space: A frame of reference for tracking
Common Extensions:
- Hand tracking
- Eye tracking
- Spatial anchors
- Composition layers
- Scene understanding

Namespace Declaration

{
  "@context": {
    "@vocab": "https://schema.org/",
    "mvmd": "https://mvmd.org/v1/",
    "openxr": "https://www.khronos.org/openxr/schema/"
  }
}

External Reference Patterns

When linking to OpenXR-compatible content:

{
  "@context": {
    "@vocab": "https://schema.org/"
  },
  "@type": "SoftwareApplication",
  "name": "XR Viewer Application",
  "applicationCategory": "VirtualRealityApplication",
  "operatingSystem": "Windows, Android",
  "softwareRequirements": "OpenXR 1.0 compatible system"
}

For more detailed hardware requirements:

{
  "@context": {
    "@vocab": "https://schema.org/"
  },
  "@type": "SoftwareApplication",
  "name": "Immersive Training Simulator",
  "applicationCategory": "VirtualRealityApplication",
  "operatingSystem": "Windows",
  "softwareRequirements": {
    "@type": "CreativeWork",
    "name": "OpenXR Requirements",
    "contentUrl": "https://example.com/app/xr-requirements.json",
    "encodingFormat": "application/json" 
  }
}

Embedding Patterns

When embedding OpenXR configuration data:

{
  "@context": {
    "@vocab": "https://schema.org/",
    "openxr": "https://www.khronos.org/openxr/schema/"
  },
  "@type": "SoftwareApplication",
  "name": "XR Experience",
  "applicationCategory": "VirtualRealityApplication",
  "openxr:requirements": {
    "minVersion": "1.0",
    "extensions": [
      "XR_EXT_hand_tracking",
      "XR_FB_display_refresh_rate"
    ],
    "formFactors": ["hmd", "handheld"]
  }
}

Implementation Examples

Complete XR experience with detailed configuration:

{
  "@context": {
    "@vocab": "https://schema.org/",
    "openxr": "https://www.khronos.org/openxr/schema/"
  },
  "@type": "SoftwareApplication",
  "name": "Immersive Educational Experience",
  "description": "Interactive exploration of historical sites in virtual reality",
  "applicationCategory": "EducationalApplication VirtualRealityApplication",
  "operatingSystem": "Windows, Android",
  "offers": {
    "@type": "Offer",
    "price": "15.99",
    "priceCurrency": "USD"
  },
  "openxr:configuration": {
    "specVersion": "1.0",
    "requiredExtensions": [
      "XR_EXT_hand_tracking",
      "XR_FB_display_refresh_rate"
    ],
    "optionalExtensions": [
      "XR_EXT_eye_gaze_interaction",
      "XR_MSFT_spatial_anchor"
    ],
    "supportedFormFactors": [
      {
        "type": "hmd",
        "recommendedDevices": ["Oculus Quest 2", "HTC Vive Pro", "Valve Index"]
      },
      {
        "type": "handheld",
        "recommendedDevices": ["Android AR compatible phones"]
      }
    ],
    "inputActions": [
      {
        "name": "grab",
        "type": "boolean",
        "defaultBindings": {
          "hmd": "squeeze/value",
          "handheld": "touchscreen/tap" 
        }
      },
      {
        "name": "navigate",
        "type": "vector2",
        "defaultBindings": {
          "hmd": "thumbstick",
          "handheld": "touchscreen/swipe"
        }
      },
      {
        "name": "select",
        "type": "boolean",
        "defaultBindings": {
          "hmd": "trigger/value",
          "handheld": "touchscreen/tap"
        }
      }
    ],
    "graphicsRequirements": {
      "recommendedGPU": "NVIDIA GTX 1070 or equivalent",
      "minimumGPU": "NVIDIA GTX 970 or equivalent",
      "preferredColorSpace": "linear"
    },
    "userExperience": {
      "comfortLevel": "moderate",
      "locomotionMethods": ["teleport", "continuous"],
      "standingExperience": true,
      "seatedExperience": true,
      "playAreaRecommended": "2m x 2m"
    }
  },
  "openxr:accessibility": {
    "subtitles": true,
    "audioDescription": true,
    "oneHandedMode": true,
    "noFlashingContent": true,
    "colorBlindOptions": true,
    "comfortSettings": {
      "adjustableFieldOfView": true,
      "motionIntensity": "adjustable",
      "snapTurning": true
    }
  }
}

Another example focused on AR application:

{
  "@context": {
    "@vocab": "https://schema.org/",
    "openxr": "https://www.khronos.org/openxr/schema/"
  },
  "@type": "SoftwareApplication",
  "name": "AR Object Visualizer",
  "description": "View 3D models in your real environment with augmented reality",
  "applicationCategory": "AugmentedRealityApplication",
  "operatingSystem": "iOS, Android",
  "openxr:configuration": {
    "specVersion": "1.0",
    "requiredExtensions": [
      "XR_MSFT_scene_understanding",
      "XR_FB_plane_detection"
    ],
    "supportedFormFactors": [
      {
        "type": "handheld",
        "recommendedDevices": ["ARKit compatible iOS devices", "ARCore compatible Android devices"]
      },
      {
        "type": "hmd",
        "recommendedDevices": ["Microsoft HoloLens 2"]
      }
    ],
    "trackingCapabilities": {
      "planarSurfaces": true,
      "environmentUnderstanding": true,
      "lightEstimation": true,
      "objectOcclusion": true,
      "imageRecognition": true
    },
    "contentPlacement": {
      "anchorTypes": ["plane", "mesh", "image"],
      "persistentAnchors": true,
      "cloudAnchors": true,
      "multiUserExperience": true
    }
  },
  "openxr:compatibility": {
    "arCore": {
      "minVersion": "1.25.0",
      "features": ["Depth API", "Cloud Anchors"]
    },
    "arKit": {
      "minVersion": "4.0",
      "features": ["People Occlusion", "Scene Reconstruction"]
    }
  }
}

Best Practices

Include both required and optional OpenXR extensions
Specify input mappings for different form factors
Document hardware requirements clearly
Include accessibility information
Provide fallbacks for devices without specific extensions
Document comfort settings for immersive experiences
Specify minimum OpenXR runtime version
Include details about tracking requirements

Implementation Considerations

Hardware Diversity: Account for different XR hardware capabilities
Input Flexibility: Design for multiple input methods
Performance Specifications: Be clear about performance requirements
Accessibility: Include accessibility features and options
Extension Support: Have fallbacks for optional extensions
Form Factor Specifics: Optimize for different device types
Platform Specifics: Note any platform-specific considerations

Practical Implementation Guide

Step 1: Basic XR Application Setup

Define Basic Application Information:

{
  "@context": {
    "@vocab": "https://schema.org/",
    "openxr": "https://www.khronos.org/openxr/schema/"
  },
  "@type": "SoftwareApplication",
  "name": "My XR App",
  "applicationCategory": "VirtualRealityApplication",
  "operatingSystem": "Windows, Android",
  "description": "An immersive XR experience"
}

Add OpenXR Version and Extensions:

{
  // ... basic properties ...
  "openxr:requirements": {
    "specVersion": "1.0",
    "requiredExtensions": [
      "XR_KHR_composition_layer_cube",
      "XR_EXT_hand_tracking"
    ],
    "optionalExtensions": [
      "XR_EXT_eye_gaze_interaction",
      "XR_FB_display_refresh_rate"
    ]
  }
}

Step 2: Hardware and Platform Configuration

Specify Device Requirements:

{
  // ... previous properties ...
  "openxr:hardware": {
    "minimumRequirements": {
      "gpu": "NVIDIA GTX 970 or equivalent",
      "cpu": "Intel i5-4590 or equivalent",
      "ram": "8 GB",
      "storage": "2 GB"
    },
    "recommendedRequirements": {
      "gpu": "NVIDIA RTX 2060 or equivalent",
      "cpu": "Intel i7-9700K or equivalent",
      "ram": "16 GB",
      "storage": "4 GB"
    }
  }
}

Define Form Factor Support:

{
  // ... previous properties ...
  "openxr:formFactors": {
    "hmd": {
      "supported": true,
      "recommendedDevices": [
        "Meta Quest 2",
        "Valve Index",
        "HP Reverb G2"
      ],
      "minimumFieldOfView": {
        "horizontal": 90,
        "vertical": 90
      }
    },
    "handheld": {
      "supported": true,
      "recommendedDevices": [
        "ARCore compatible phones",
        "ARKit compatible phones"
      ]
    }
  }
}

Step 3: Input and Interaction Configuration

Define Input Actions:

{
  // ... previous properties ...
  "openxr:input": {
    "actions": [
      {
        "name": "hand_pose",
        "type": "pose",
        "requirements": ["XR_EXT_hand_tracking"],
        "bindings": {
          "hmd": "/user/hand/left/input/aim/pose",
          "handheld": "/user/hand/grip/pose"
        }
      },
      {
        "name": "select_object",
        "type": "boolean",
        "bindings": {
          "hmd": "/user/hand/right/input/trigger/value",
          "handheld": "/user/hand/grip/value"
        }
      }
    ],
    "actionSets": [
      {
        "name": "gameplay",
        "priority": 1,
        "actions": ["hand_pose", "select_object"]
      }
    ]
  }
}

Step 4: User Experience and Comfort Settings

Configure Comfort Options:

{
  // ... previous properties ...
  "openxr:comfort": {
    "locomotion": {
      "methods": ["teleport", "smooth"],
      "defaultMethod": "teleport",
      "turnOptions": {
        "snap": true,
        "smooth": true,
        "defaultAngle": 45
      },
      "vignette": {
        "enabled": true,
        "intensity": 0.7
      }
    },
    "posture": {
      "standing": true,
      "seated": true,
      "roomScale": true,
      "minPlayArea": {
        "width": 1.5,
        "depth": 1.5
      }
    }
  }
}

Add Accessibility Features:

{
  // ... previous properties ...
  "openxr:accessibility": {
    "visual": {
      "subtitles": true,
      "highContrast": true,
      "colorblindModes": ["protanopia", "deuteranopia", "tritanopia"],
      "textScaling": true
    },
    "audio": {
      "spatialAudio": true,
      "audioDescription": true,
      "hearingAidSupport": true
    },
    "physical": {
      "oneHandedMode": true,
      "seatedMode": true,
      "reducedMotion": true
    }
  }
}

Step 5: Platform-Specific Implementation

AR Implementation:

{
  // ... previous properties ...
  "openxr:ar": {
    "features": {
      "planeDetection": true,
      "imageTracking": true,
      "meshGeneration": true,
      "lightEstimation": true
    },
    "anchors": {
      "local": true,
      "cloud": true,
      "persistence": true
    },
    "occlusion": {
      "environmental": true,
      "people": true
    }
  }
}

VR Implementation:

{
  // ... previous properties ...
  "openxr:vr": {
    "rendering": {
      "resolution": {
        "default": "native",
        "scalingOptions": [0.7, 1.0, 1.2, 1.5]
      },
      "refreshRate": {
        "minimum": 72,
        "recommended": 90,
        "maximum": 120
      }
    },
    "tracking": {
      "headset": "6dof",
      "controllers": "6dof",
      "hands": "skeletal",
      "eyes": "gaze"
    }
  }
}

Best Practices for Implementation

Version Management:
- Always specify OpenXR version requirements
- List required and optional extensions separately
- Include fallbacks for unsupported features
- Document version-specific features
Hardware Compatibility:
- Define clear minimum requirements
- List recommended specifications
- Support multiple form factors when possible
- Include device-specific optimizations
Input Handling:
- Design for multiple input methods
- Support both VR and AR interactions
- Implement fallbacks for unsupported inputs
- Use standard action mappings
Performance Optimization:
- Implement dynamic resolution scaling
- Support multiple quality presets
- Monitor and adjust refresh rates
- Optimize for mobile VR/AR

Troubleshooting Common Issues

Extension Support:
- Check extension availability at runtime
- Provide fallback functionality
- Log unsupported features
- Handle graceful degradation
Input Problems:
- Validate action bindings
- Test across different devices
- Support multiple input methods
- Handle disconnection events
Performance Issues:
- Monitor frame timing
- Implement dynamic quality scaling
- Check GPU/CPU utilization
- Optimize render pipeline
Platform Compatibility:
- Test on target platforms
- Verify extension support
- Check hardware capabilities
- Validate tracking requirements

Overview and Use Cases​

Core Properties and Extensions​

Namespace Declaration​

External Reference Patterns​

Embedding Patterns​

Implementation Examples​

Best Practices​

Implementation Considerations​

Related Concepts​

Practical Implementation Guide​

Step 1: Basic XR Application Setup​

Step 2: Hardware and Platform Configuration​

Step 3: Input and Interaction Configuration​

Step 4: User Experience and Comfort Settings​

Step 5: Platform-Specific Implementation​

Best Practices for Implementation​

Troubleshooting Common Issues​