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Add docs to clarify writing Intersection Matrix functions #1135

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Jan 10, 2024
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Add docs to clarify writing Intersection Matrix functions #1135

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7e35154
Document relationship between CoordPos relationships and DE9-IM matrices
urschrei Jan 3, 2024
ccc438b
clarify relationship between IntersectionMatrix and DE9-IM matrix
urschrei Jan 4, 2024
9c4f5b1
Merge branch 'main' into document_relate
urschrei Jan 10, 2024
91e5dac
Update changelog
urschrei Jan 10, 2024
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2 changes: 2 additions & 0 deletions geo/CHANGES.md
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Expand Up @@ -32,6 +32,8 @@
* <https://github.com/georust/geo/pull/1134>
* Add topological equality comparison method:
* <https://github.com/georust/geo/pull/1133>
* Add docs to Relate trait
* <https://github.com/georust/geo/pull/1135>

## 0.27.0

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34 changes: 34 additions & 0 deletions geo/src/algorithm/relate/geomgraph/intersection_matrix.rs
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Expand Up @@ -188,6 +188,40 @@ impl IntersectionMatrix {
Ok(())
}

// NOTE for implementers
// See https://en.wikipedia.org/wiki/DE-9IM#Spatial_predicates for a mapping between predicates and matrices
// The number of constraints in your relation function MUST match the number of NON-MASK (T or F) matrix entries

// Indexes of the IntersectionMatrix map to indexes of a DE-9IM specification string as follows:
// ==================================================================
// self.0[CoordPos::Inside][CoordPos::Inside]: 0
// self.0[CoordPos::Inside][CoordPos::OnBoundary]: 1
// self.0[CoordPos::Inside][CoordPos::Outside]: 2

// self.0[CoordPos::OnBoundary][CoordPos::Inside]: 3
// self.0[CoordPos::OnBoundary][CoordPos::OnBoundary]: 4
// self.0[CoordPos::OnBoundary][CoordPos::Outside]: 5

// self.0[CoordPos::Outside][CoordPos::Inside]: 6
// self.0[CoordPos::Outside][CoordPos::OnBoundary]: 7
// self.0[CoordPos::Outside][CoordPos::Outside]: 8
// ==================================================================

// Relationship between matrix entry and Dimensions
// ==================================================================
// A `T` entry translates to `!= Dimensions::Empty`
// An `F` entry translates to `== Dimensions::Empty`
// A `*` (mask) entry is OMITTED
// ==================================================================

// Examples
// ==================================================================
// `[T********]` -> `self.0[CoordPos::Inside][CoordPos::Inside] != Dimensions::Empty`
// `[********F]` -> `self.0[CoordPos::Outside][CoordPos::Outside] == Dimensions::Empty`
// `[**T****F*]` -> `self.0[CoordPos::Inside][CoordPos::Outside] != Dimensions::Empty
// && self.0[CoordPos::Outside][CoordPos::OnBoundary] == Dimensions::Empty`
// ==================================================================

/// Tests if this matrix matches `[FF*FF****]`.
///
/// returns `true` if the two geometries related by this matrix are disjoint
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