Add computeLevelDenominator.

CesiumGS · Nov 8, 2023 · 5def156 · 5def156
1 parent 75f545b
commit 5def156
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Showing 2 changed files with 22 additions and 4 deletions.
diff --git a/Cesium3DTilesContent/include/Cesium3DTilesContent/ImplicitTilingUtilities.h b/Cesium3DTilesContent/include/Cesium3DTilesContent/ImplicitTilingUtilities.h
@@ -328,6 +328,19 @@ class ImplicitTilingUtilities {
   static CesiumGeospatial::S2CellBoundingVolume computeBoundingVolume(
       const CesiumGeospatial::S2CellBoundingVolume& rootBoundingVolume,
       const CesiumGeometry::QuadtreeTileID& tileID) noexcept;
+
+  /**
+   * @brief Computes the denominator for a given implicit tile level.
+   *
+   * Divide the root tile's geometric error by this value to get the standard
+   * geometric error for tiles on the level. Or divide each component of a
+   * bounding volume by this factor to get the size of the bounding volume along
+   * that axis for tiles of this level.
+   *
+   * @param level The tile level.
+   * @return The denominator for the level.
+   */
+  static double computeLevelDenominator(uint32_t level) noexcept;
 };
 
 } // namespace Cesium3DTilesContent
diff --git a/Cesium3DTilesContent/src/ImplicitTilingUtilities.cpp b/Cesium3DTilesContent/src/ImplicitTilingUtilities.cpp
@@ -156,7 +156,7 @@ CesiumGeospatial::GlobeRectangle subdivideRectangle(
 CesiumGeospatial::BoundingRegion ImplicitTilingUtilities::computeBoundingVolume(
     const CesiumGeospatial::BoundingRegion& rootBoundingVolume,
     const CesiumGeometry::QuadtreeTileID& tileID) noexcept {
-  double denominator = static_cast<double>(1 << tileID.level);
+  double denominator = computeLevelDenominator(tileID.level);
   return CesiumGeospatial::BoundingRegion{
       subdivideRectangle(
           rootBoundingVolume.getRectangle(),
@@ -169,7 +169,7 @@ CesiumGeospatial::BoundingRegion ImplicitTilingUtilities::computeBoundingVolume(
 CesiumGeospatial::BoundingRegion ImplicitTilingUtilities::computeBoundingVolume(
     const CesiumGeospatial::BoundingRegion& rootBoundingVolume,
     const CesiumGeometry::OctreeTileID& tileID) noexcept {
-  double denominator = static_cast<double>(1 << tileID.level);
+  double denominator = computeLevelDenominator(tileID.level);
   double heightSize = (rootBoundingVolume.getMaximumHeight() -
                        rootBoundingVolume.getMinimumHeight()) /
                       denominator;
@@ -195,7 +195,7 @@ ImplicitTilingUtilities::computeBoundingVolume(
   const glm::dmat3& halfAxes = rootBoundingVolume.getHalfAxes();
   const glm::dvec3& center = rootBoundingVolume.getCenter();
 
-  double denominator = static_cast<double>(1 << tileID.level);
+  double denominator = computeLevelDenominator(tileID.level);
   glm::dvec3 min = center - halfAxes[0] - halfAxes[1] - halfAxes[2];
 
   glm::dvec3 xDim = halfAxes[0] * 2.0 / denominator;
@@ -216,7 +216,7 @@ ImplicitTilingUtilities::computeBoundingVolume(
   const glm::dmat3& halfAxes = rootBoundingVolume.getHalfAxes();
   const glm::dvec3& center = rootBoundingVolume.getCenter();
 
-  double denominator = static_cast<double>(1 << tileID.level);
+  double denominator = computeLevelDenominator(tileID.level);
   glm::dvec3 min = center - halfAxes[0] - halfAxes[1] - halfAxes[2];
 
   glm::dvec3 xDim = halfAxes[0] * 2.0 / denominator;
@@ -245,6 +245,11 @@ ImplicitTilingUtilities::computeBoundingVolume(
       rootBoundingVolume.getMaximumHeight());
 }
 
+double
+ImplicitTilingUtilities::computeLevelDenominator(uint32_t level) noexcept {
+  return static_cast<double>(1 << level);
+}
+
 QuadtreeChildren::iterator::iterator(
     const CesiumGeometry::QuadtreeTileID& parentTileID,
     bool isEnd) noexcept