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voxel_downsample

rigidity_core::voxel

Function voxel_downsample 

Source 
pub fn voxel_downsample(
    cloud: &PointCloud,
    voxel_size: f64,
) -> Result<PointCloud, CloudError>
Expand description

Downsamples a cloud onto a grid of cells with edge voxel_size, replacing the points of each occupied cell by their centroid.

§Determinism

The result is bit-for-bit identical at any thread count, both in values and in point order. This is a requirement, not a side effect: further up the stack these points assemble the Jacobian, and a floating order of summation would make the smallest singular value float — that is, the degeneracy detector itself.

Three decisions achieve it:

  1. points are sorted by the key (cell, original index), which is a total order, so the sorted sequence is unique regardless of the sorting algorithm;
  2. within a cell, accumulation runs sequentially in increasing original index, so the order of summation is fixed;
  3. parallelism happens only between cells, which are independent.

A hash table instead of the sort would be faster, but neither its traversal order nor its order of merging partial sums is defined.

§Attributes

Attributes are not carried over: averaging depends on what the column means — colour averages, a class label does not. The returned cloud has coordinates only.