ส่วนขยาย OpenXR ของ XR_ANDROID_scene_meshing

typedef struct XrSystemSceneMeshingPropertiesANDROID {
    XrStructureType    type;
    void*              next;
    XrBool32           supportsSceneMeshing;
} XrSystemSceneMeshingPropertiesANDROID;

typedef enum XrSceneMeshSemanticLabelSetANDROID {
    XR_SCENE_MESH_SEMANTIC_LABEL_SET_NONE_ANDROID = 0,
    XR_SCENE_MESH_SEMANTIC_LABEL_SET_DEFAULT_ANDROID = 1,
    XR_SCENE_MESH_SEMANTIC_LABEL_SET_MAX_ENUM_ANDROID = 0x7FFFFFFF
} XrSceneMeshSemanticLabelSetANDROID;

XrResult xrEnumerateSupportedSemanticLabelSetsANDROID(
    XrInstance                                  instance,
    XrSystemId                                  systemId,
    uint32_t                                    supportedSemanticLabelSetsInputCapacity,
    uint32_t*                                   supportedSemanticLabelSetsOutputCount,
    XrSceneMeshSemanticLabelSetANDROID*         supportedSemanticLabelSets);

XR_DEFINE_HANDLE(XrSceneMeshingTrackerANDROID)

XrResult xrCreateSceneMeshingTrackerANDROID(
    XrSession                                   session,
    const XrSceneMeshingTrackerCreateInfoANDROID* createInfo,
    XrSceneMeshingTrackerANDROID*               tracker);

typedef struct XrSceneMeshingTrackerCreateInfoANDROID {
    XrStructureType                       type;
    const void*                           next;
    XrSceneMeshSemanticLabelSetANDROID    semanticLabelSet;
    XrBool32                              enableNormals;
} XrSceneMeshingTrackerCreateInfoANDROID;

XrResult xrDestroySceneMeshingTrackerANDROID(
    XrSceneMeshingTrackerANDROID          tracker);

XR_DEFINE_HANDLE(XrSceneMeshSnapshotANDROID)

typedef struct XrSceneMeshSnapshotCreateInfoANDROID {
    XrStructureType    type;
    const void*        next;
    XrSpace            baseSpace;
    XrTime             time;
    XrBoxf             boundingBox;
} XrSceneMeshSnapshotCreateInfoANDROID;

typedef enum XrSceneMeshTrackingStateANDROID {
    XR_SCENE_MESH_TRACKING_STATE_INITIALIZING_ANDROID = 0,
    XR_SCENE_MESH_TRACKING_STATE_TRACKING_ANDROID = 1,
    XR_SCENE_MESH_TRACKING_STATE_WAITING_ANDROID = 2,
    XR_SCENE_MESH_TRACKING_STATE_ERROR_ANDROID = 3,
    XR_SCENE_MESH_TRACKING_STATE_MAX_ENUM_ANDROID = 0x7FFFFFFF
} XrSceneMeshTrackingStateANDROID;

typedef struct XrSceneMeshSnapshotCreationResultANDROID {
    XrStructureType                  type;
    void*                            next;
    XrSceneMeshSnapshotANDROID       snapshot;
    XrSceneMeshTrackingStateANDROID    trackingState;
} XrSceneMeshSnapshotCreationResultANDROID;

XrResult xrCreateSceneMeshSnapshotANDROID(
    XrSceneMeshingTrackerANDROID                tracker,
    const XrSceneMeshSnapshotCreateInfoANDROID* createInfo,
    XrSceneMeshSnapshotCreationResultANDROID*   outSnapshotCreationResult);

typedef struct XrSceneSubmeshStateANDROID {
    XrStructureType    type;
    void*              next;
    XrUuid             submeshId;
    XrTime             lastUpdatedTime;
    XrPosef            submeshPoseInBaseSpace;
    XrExtent3Df        bounds;
} XrSceneSubmeshStateANDROID;

XrResult xrGetAllSubmeshStatesANDROID(
    XrSceneMeshSnapshotANDROID            snapshot,
    uint32_t                              submeshStateCapacityInput,
    uint32_t*                             submeshStateCountOutput,
    XrSceneSubmeshStateANDROID*           submeshStates);

typedef struct XrSceneSubmeshDataANDROID {
    XrStructureType    type;
    const void*        next;
    XrUuid             submeshId;
    uint32_t           vertexCapacityInput;
    uint32_t           vertexCountOutput;
    XrVector3f*        vertexPositions;
    XrVector3f*        vertexNormals;
    uint8_t*           vertexSemantics;
    uint32_t           indexCapacityInput;
    uint32_t           indexCountOutput;
    uint32_t*          indices;
} XrSceneSubmeshDataANDROID;

XrResult xrGetSubmeshDataANDROID(
    XrSceneMeshSnapshotANDROID            snapshot,
    uint32_t                              submeshDataCount,
    XrSceneSubmeshDataANDROID*            inoutSubmeshData);

typedef enum XrSceneMeshSemanticLabelANDROID {
    XR_SCENE_MESH_SEMANTIC_LABEL_OTHER_ANDROID = 0,
    XR_SCENE_MESH_SEMANTIC_LABEL_FLOOR_ANDROID = 1,
    XR_SCENE_MESH_SEMANTIC_LABEL_CEILING_ANDROID = 2,
    XR_SCENE_MESH_SEMANTIC_LABEL_WALL_ANDROID = 3,
    XR_SCENE_MESH_SEMANTIC_LABEL_TABLE_ANDROID = 4,
    XR_SCENE_MESH_SEMANTIC_LABEL_MAX_ENUM_ANDROID = 0x7FFFFFFF
} XrSceneMeshSemanticLabelANDROID;

XrResult xrDestroySceneMeshSnapshotANDROID(
    XrSceneMeshSnapshotANDROID            snapshot);

XrInstance instance;  // Created at app startup
XrSystemId systemId;  // Received from xrGetSystem() at app startup
XrSession session;    // Created at app startup
XrSpace appPlaySpace; // Created at app startup

// The function pointers are previously initialized using xrGetInstanceProcAddr.
PFN_xrCreateSceneMeshingTrackerANDROID xrCreateSceneMeshingTrackerANDROID;
PFN_xrDestroySceneMeshingTrackerANDROID xrDestroySceneMeshingTrackerANDROID;
PFN_xrEnumerateSupportedSemanticLabelSetsANDROID xrEnumerateSupportedSemanticLabelSetsANDROID;
PFN_xrCreateSceneMeshSnapshotANDROID xrCreateSceneMeshSnapshotANDROID;
PFN_xrDestroySceneMeshSnapshotANDROID xrDestroySceneMeshSnapshotANDROID;
PFN_xrGetAllSubmeshStatesANDROID xrGetAllSubmeshStatesANDROID;
PFN_xrGetSubmeshDataANDROID xrGetSubmeshDataANDROID;

// Inspect system capability
XrSystemSceneMeshingPropertiesANDROID sceneMeshingProps = {
  .type = XR_TYPE_SYSTEM_SCENE_MESHING_PROPERTIES_ANDROID,
};
XrSystemProperties sysProps = {
  .type = XR_TYPE_SYSTEM_PROPERTIES,
  .next = &sceneMeshingProps
};
CHK_XR(xrGetSystemProperties(instance, systemId, &sysProps));
if (!sceneMeshingProps.supportsSceneMeshing) {
    // scene meshing is not supported.
    return;
}

uint32_t supportedsemanticLabelSetsCount = 0;
xrEnumerateSupportedSemanticLabelSetsANDROID(
  instance, systemId, 0, &supportedsemanticLabelSetsCount, nullptr);
std::vector<XrSceneMeshSemanticLabelSetANDROID> supportedSemanticLabelSets(
  supportedsemanticLabelSetsCount);
xrEnumerateSupportedSemanticLabelSetsANDROID(
  instance, systemId, supportedsemanticLabelSetsCount,
  &supportedsemanticLabelSetsCount, supportedSemanticLabelSets.data());

XrSceneMeshSemanticLabelSetANDROID semanticLabelSet = XR_SCENE_MESH_SEMANTIC_LABEL_SET_NONE_ANDROID;
// Check if system supports XR_SCENE_MESH_SEMANTIC_LABEL_SET_DEFAULT_ANDROID
if (std::find(supportedSemanticLabelSets.begin(), supportedSemanticLabelSets.end(),
              XR_SCENE_MESH_SEMANTIC_LABEL_SET_DEFAULT_ANDROID) !=
    supportedSemanticLabelSets.end()) {
  semanticLabelSet = XR_SCENE_MESH_SEMANTIC_LABEL_SET_DEFAULT_ANDROID;
}

XrSceneMeshingTrackerCreateInfoANDROID trackerCreateInfo = {
  .type = XR_TYPE_SCENE_MESHING_TRACKER_CREATE_INFO_ANDROID,
  .semanticLabelSet = semanticLabelSet,
  .enableNormals = XR_TRUE
};

XrSceneMeshingTrackerANDROID tracker = XR_NULL_HANDLE;
CHK_XR(xrCreateSceneMeshingTrackerANDROID(session, &trackerCreateInfo, &tracker));

XrSceneMeshSnapshotCreationResultANDROID snapshotResult = {
  .type = XR_TYPE_SCENE_MESH_SNAPSHOT_CREATION_RESULT_ANDROID,
  .snapshot = XR_NULL_HANDLE
};
XrSceneMeshSnapshotANDROID& snapshot = snapshotResult.snapshot;
XrSceneMeshSnapshotCreateInfoANDROID createInfo = {
  .type = XR_TYPE_SCENE_MESH_SNAPSHOT_CREATE_INFO_ANDROID
};

// app update loop
while (true) {
  // ...
  // For every frame in frame loop
  // ...

  XrFrameState frameState; // previously returned from xrWaitFrame
  const XrTime time = frameState.predictedDisplayTime;
  XrBoxf box; // populated with the bounding box of the camera frustum

  // ...

  createInfo.baseSpace = appPlaySpace;
  createInfo.time = time;
  createInfo.boundingBox = box;

  // Grab the scene mesh snapshot. This way the app can: know all of the submesh infos,
  // choose the appropriate submeshes for which to get data, allocate the necessary
  // buffer for those submeshes, and then get the data.
  CHK_XR(xrCreateSceneMeshSnapshotANDROID(tracker, &createInfo, &snapshotResult));

  // check the tracking state
  if (snapshotResult.trackingState == XR_SCENE_MESH_TRACKING_STATE_ERROR_ANDROID) {
    // unrecoverable error. Exit the app.
    if (snapshot != XR_NULL_HANDLE) {
      CHK_XR(xrDestroySceneMeshSnapshotANDROID(snapshot));
      snapshot = XR_NULL_HANDLE;
    }
    break;
  } else if (snapshotResult.trackingState != XR_SCENE_MESH_TRACKING_STATE_TRACKING_ANDROID) {
    // The tracker is not tracking. Try again later.
    if (snapshot != XR_NULL_HANDLE) {
      CHK_XR(xrDestroySceneMeshSnapshotANDROID(snapshot));
      snapshot = XR_NULL_HANDLE;
    }
    continue;
  }

  // 2-call idiom for getting submesh states
  std::vector<XrSceneSubmeshStateANDROID> states;
  uint32_t submeshCount = 0;
  CHK_XR(xrGetAllSubmeshStatesANDROID(snapshot, 0, &submeshCount, nullptr));
  states.resize(submeshCount);
  for (XrSceneSubmeshStateANDROID& state : states) {
    state = {.type = XR_TYPE_SCENE_SUBMESH_STATE_ANDROID};
  }
  CHK_XR(xrGetAllSubmeshStatesANDROID(snapshot, submeshCount, &submeshCount, states.data()));

  // To store the poses for the selected submeshes
  std::vector<XrPosef> submeshesPoses;
  submeshesPoses.reserve(submeshCount);

  std::vector<XrSceneSubmeshDataANDROID> submeshes;
  submeshes.reserve(submeshCount);
  // Iterate the states and determine which submeshes the app wants data for
  for (XrSceneSubmeshStateANDROID& state : states) {
    // Modify this bool as necessary by looking at states. Maybe state.lastUpdatedTime
    // is below a threshold or maybe the bounding box does not intersect with camera view
    // frustum (The submesh will be culled).
    bool needed;
    if (needed) {
      // Add the selected submesh to the submeshes list. Set the capacity
      // zero for now since the size of the buffer will be determined later.
      XrSceneSubmeshDataANDROID submesh = {
        .type = XR_TYPE_SCENE_SUBMESH_DATA_ANDROID,
        .submeshId = state.submeshId,
        .vertexCapacityInput = 0,
        .vertexCountOutput = 0,
        .vertexPositions = nullptr,
        .vertexNormals = nullptr,
        .vertexSemantics = nullptr,
        .indexCapacityInput = 0,
        .indexCountOutput = 0,
        .indices = nullptr,
      };
      submeshes.push_back(submesh);
      submeshesPoses.push_back(state.submeshPoseInBaseSpace);
    }
  }

  // Grab the data for the selected submeshes using the 2-call idiom.
  CHK_XR(xrGetSubmeshDataANDROID(snapshot, submeshes.size(), submeshes.data()));
  for (XrSceneSubmeshDataANDROID& submesh : submeshes) {
    submesh.vertexCapacityInput = submesh.vertexCountOutput;
    submesh.vertexCountOutput = 0;
    submesh.vertexPositions = new XrVector3f[submesh.vertexCountOutput];
    submesh.vertexNormals = new XrVector3f[submesh.vertexCountOutput];
    submesh.vertexSemantics = new uint8_t[submesh.vertexCountOutput];
    submesh.indexCapacityInput = submesh.indexCountOutput;
    submesh.indexCountOutput = 0;
    submesh.indices = new uint32_t[submesh.indexCountOutput];
  }
  CHK_XR(xrGetSubmeshDataANDROID(snapshot, submeshes.size(), submeshes.data()));

  // Destroy the scene mesh snapshot since we have finally grabbed the submeshes data. In
  // next iteration app can: create a new one to get latest mesh data
  CHK_XR(xrDestroySceneMeshSnapshotANDROID(snapshot));
  snapshot = XR_NULL_HANDLE;

  // Iterate the submeshes and get the vertex positions, vertex normals and
  // vertex semantics data for the selected submeshes
  for (uint32_t i = 0; i < submeshes.size(); i++) {
    XrSceneSubmeshDataANDROID& data = submeshes[i];
    XrVector3f* vertexPositions = data.vertexPositions;
    XrVector3f* vertexNormals = data.vertexNormals;
    XrSceneMeshSemanticLabelANDROID* vertexSemantics =
      reinterpret_cast<XrSceneMeshSemanticLabelANDROID*>(data.vertexSemantics);
    XrPosef pose = submeshesPoses[i];

    // *** Use the data as per needs ***

    // Release the allocated memory for the data buffers when done using
    delete [] data.vertexPositions;
    delete [] data.vertexNormals;
    delete [] data.vertexSemantics;
    delete [] data.indices;
  }

  // ...
  // Finish frame loop
  // ...
}

CHK_XR(xrDestroySceneMeshingTrackerANDROID(tracker));