| 68 | _pRoot(nullptr) {} |
| 69 | |
| 70 | uint8_t QuadtreeAvailability::computeAvailability( |
| 71 | const QuadtreeTileID& tileID) const noexcept { |
| 72 | |
| 73 | // The root tile and root tile's subtree are implicitly available. |
| 74 | if (!this->_pRoot && tileID.level == 0) { |
| 75 | return TileAvailabilityFlags::TILE_AVAILABLE | |
| 76 | TileAvailabilityFlags::SUBTREE_AVAILABLE; |
| 77 | } |
| 78 | |
| 79 | if (!this->_pRoot || tileID.level > this->_maximumLevel) { |
| 80 | return 0; |
| 81 | } |
| 82 | |
| 83 | uint32_t level = 0; |
| 84 | AvailabilityNode* pNode = this->_pRoot.get(); |
| 85 | |
| 86 | while (pNode && pNode->subtree && tileID.level >= level) { |
| 87 | const AvailabilitySubtree& subtree = *pNode->subtree; |
| 88 | |
| 89 | AvailabilityAccessor tileAvailabilityAccessor( |
| 90 | subtree.tileAvailability, |
| 91 | subtree); |
| 92 | AvailabilityAccessor contentAvailabilityAccessor( |
| 93 | subtree.contentAvailability, |
| 94 | subtree); |
| 95 | AvailabilityAccessor subtreeAvailabilityAccessor( |
| 96 | subtree.subtreeAvailability, |
| 97 | subtree); |
| 98 | |
| 99 | uint32_t levelsLeft = tileID.level - level; |
| 100 | uint32_t subtreeRelativeMask = ~(0xFFFFFFFF << levelsLeft); |
| 101 | |
| 102 | if (levelsLeft < this->_subtreeLevels) { |
| 103 | // The availability info is within this subtree. |
| 104 | uint8_t availability = TileAvailabilityFlags::REACHABLE; |
| 105 | |
| 106 | uint32_t relativeMortonIndex = getMortonIndex( |
| 107 | tileID.x & subtreeRelativeMask, |
| 108 | tileID.y & subtreeRelativeMask); |
| 109 | |
| 110 | // For reference: |
| 111 | // https://github.com/CesiumGS/3d-tiles/tree/3d-tiles-next/extensions/3DTILES_implicit_tiling#availability-bitstream-lengths |
| 112 | // The below is identical to: |
| 113 | // (4^levelRelativeToSubtree - 1) / 3 |
| 114 | uint32_t offset = ((1U << (levelsLeft << 1U)) - 1U) / 3U; |
| 115 | |
| 116 | uint32_t availabilityIndex = relativeMortonIndex + offset; |
| 117 | uint32_t byteIndex = availabilityIndex >> 3; |
| 118 | uint8_t bitIndex = static_cast<uint8_t>(availabilityIndex & 7); |
| 119 | uint8_t bitMask = static_cast<uint8_t>(1 << bitIndex); |
| 120 | |
| 121 | // Check tile availability. |
| 122 | if ((tileAvailabilityAccessor.isConstant() && |
| 123 | tileAvailabilityAccessor.getConstant()) || |
| 124 | (tileAvailabilityAccessor.isBufferView() && |
| 125 | (uint8_t)tileAvailabilityAccessor[byteIndex] & bitMask)) { |
| 126 | availability |= TileAvailabilityFlags::TILE_AVAILABLE; |
| 127 | } |
nothing calls this directly
no test coverage detected