Intersection

Intersections are implemented for various geometries and domains with the ∩ (\cap) operator:

using Meshes

s1 = Segment((0.0,0.0), (1.0,0.0))
s2 = Segment((0.5,0.0), (2.0,0.0))

s1 ∩ s2

Segment
├─ Point(x: 0.5 m, y: 0.0 m)
└─ Point(x: 1.0 m, y: 0.0 m)

First, the intersection function computes the Intersection object, which holds the IntersectionType besides the actual geometry:

I = intersection(s1, s2)

Intersection{Segment{𝔼{2}, CoordRefSystems.Cartesian2D{CoordRefSystems.NoDatum, Unitful.Quantity{Float64, 𝐋, Unitful.FreeUnits{(m,), 𝐋, nothing}}}}}(Overlapping, Segment((x: 0.5 m, y: 0.0 m), (x: 1.0 m, y: 0.0 m)))

This object supports two methods type and get to retrieve the underlying information:

type(I)

Overlapping::IntersectionType = 6

get(I)

Segment
├─ Point(x: 0.5 m, y: 0.0 m)
└─ Point(x: 1.0 m, y: 0.0 m)

For performance-sensitive code, it is recommended to use the intersection method with three arguments, including a function to reduce the number of output types.

In the example below, we use the do syntax to restrict our attention to a subset of intersection types and to make the return type and Int value in all cases:

intersection(s1, s2) do I
  if type(I) == Crossing
    return 1
  elseif type(I) == Overlapping
    return 2
  else
    return 3
  end
end

Meshes.IntersectionType — Type

IntersectionType

The different types of intersection that may occur between geometries. Type IntersectionType in a Julia session to see the full list.

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Meshes.Intersection — Type

Intersection{G}

An intersection between geometries holding a geometry of type G.

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Meshes.intersection — Function

intersection([f], g₁, g₂)

Compute the intersection of two geometries or domains g₁ and g₂ and apply function f to it. Default function is identity.

Examples

intersection(g₁, g₂) do I
  if I isa CrossingLines
    # do something
  else
    # do nothing
  end
end

Notes

When a custom function f is used that reduces the number of return types, Julia is able to optimize the branches of the code and generate specialized code. This is not the case when f === identity.

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Base.intersect — Method

g₁ ∩ g₂

Return the intersection of two geometries or domains g₁ and g₂ as a new (multi-)geometry.

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