message: Added const accessor for voxel.
diff: @@ -181,6 +181,20 @@ class Layer {
  return &voxel;
  }
  + inline const VoxelType* getVoxelPtrByGlobalIndex(
  + const VoxelIndex& global_voxel_index) const {
  + const BlockIndex block_index = getBlockIndexFromGlobalVoxelIndex(
  + global_voxel_index, voxels_per_side_inv_);
  + if (!hasBlock(block_index)) {
  + return nullptr;
  + }
  + const VoxelIndex local_voxel_index = getLocalFromGlobalVoxelIndex(
  + global_voxel_index, voxels_per_side_);
  + const Block<VoxelType>& block = getBlockByIndex(block_index);
  + const VoxelType& voxel = block.getVoxelByVoxelIndex(local_voxel_index);
  + return &voxel;
  + }
  +
  FloatingPoint block_size() const { return block_size_; }
  FloatingPoint voxel_size() const { return voxel_size_; }
  size_t voxels_per_side() const { return voxels_per_side_; }
  