150 lines
6.6 KiB
Go
150 lines
6.6 KiB
Go
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// Copyright 2019 Google Inc. All rights reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package s2
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import (
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"github.com/golang/geo/s1"
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)
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// The distance interface represents a set of common methods used by algorithms
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// that compute distances between various S2 types.
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type distance interface {
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// chordAngle returns this type as a ChordAngle.
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chordAngle() s1.ChordAngle
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// fromChordAngle is used to type convert a ChordAngle to this type.
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// This is to work around needing to be clever in parts of the code
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// where a distanceTarget interface method expects distances, but the
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// user only supplies a ChordAngle, and we need to dynamically cast it
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// to an appropriate distance interface types.
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fromChordAngle(o s1.ChordAngle) distance
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// zero returns a zero distance.
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zero() distance
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// negative returns a value smaller than any valid value.
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negative() distance
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// infinity returns a value larger than any valid value.
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infinity() distance
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// less is similar to the Less method in Sort. To get minimum values,
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// this would be a less than type operation. For maximum, this would
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// be a greater than type operation.
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less(other distance) bool
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// sub subtracts the other value from this one and returns the new value.
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// This is done as a method and not simple mathematical operation to
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// allow closest and furthest to implement this in opposite ways.
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sub(other distance) distance
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// chordAngleBound reports the upper bound on a ChordAngle corresponding
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// to this distance. For example, if distance measures WGS84 ellipsoid
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// distance then the corresponding angle needs to be 0.56% larger.
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chordAngleBound() s1.ChordAngle
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// updateDistance may update the value this distance represents
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// based on the given input. The updated value and a boolean reporting
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// if the value was changed are returned.
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updateDistance(other distance) (distance, bool)
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}
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// distanceTarget is an interface that represents a geometric type to which distances
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// are measured.
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//
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// For example, there are implementations that measure distances to a Point,
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// an Edge, a Cell, a CellUnion, and even to an arbitrary collection of geometry
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// stored in ShapeIndex.
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//
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// The distanceTarget types are provided for the benefit of types that measure
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// distances and/or find nearby geometry, such as ClosestEdgeQuery, FurthestEdgeQuery,
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// ClosestPointQuery, and ClosestCellQuery, etc.
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type distanceTarget interface {
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// capBound returns a Cap that bounds the set of points whose distance to the
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// target is distance.zero().
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capBound() Cap
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// updateDistanceToPoint updates the distance if the distance to
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// the point P is within than the given dist.
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// The boolean reports if the value was updated.
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updateDistanceToPoint(p Point, dist distance) (distance, bool)
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// updateDistanceToEdge updates the distance if the distance to
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// the edge E is within than the given dist.
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// The boolean reports if the value was updated.
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updateDistanceToEdge(e Edge, dist distance) (distance, bool)
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// updateDistanceToCell updates the distance if the distance to the cell C
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// (including its interior) is within than the given dist.
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// The boolean reports if the value was updated.
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updateDistanceToCell(c Cell, dist distance) (distance, bool)
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// setMaxError potentially updates the value of MaxError, and reports if
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// the specific type supports altering it. Whenever one of the
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// updateDistanceTo... methods above returns true, the returned distance
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// is allowed to be up to maxError larger than the true minimum distance.
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// In other words, it gives this target object permission to terminate its
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// distance calculation as soon as it has determined that (1) the minimum
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// distance is less than minDist and (2) the best possible further
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// improvement is less than maxError.
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//
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// If the target takes advantage of maxError to optimize its distance
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// calculation, this method must return true. (Most target types will
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// default to return false.)
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setMaxError(maxErr s1.ChordAngle) bool
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// maxBruteForceIndexSize reports the maximum number of indexed objects for
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// which it is faster to compute the distance by brute force (e.g., by testing
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// every edge) rather than by using an index.
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//
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// The following method is provided as a convenience for types that compute
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// distances to a collection of indexed geometry, such as ClosestEdgeQuery
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// and ClosestPointQuery.
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//
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// Types that do not support this should return a -1.
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maxBruteForceIndexSize() int
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// distance returns an instance of the underlying distance type this
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// target uses. This is to work around the use of Templates in the C++.
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distance() distance
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// visitContainingShapes finds all polygons in the given index that
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// completely contain a connected component of the target geometry. (For
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// example, if the target consists of 10 points, this method finds
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// polygons that contain any of those 10 points.) For each such polygon,
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// the visit function is called with the Shape of the polygon along with
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// a point of the target geometry that is contained by that polygon.
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//
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// Optionally, any polygon that intersects the target geometry may also be
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// returned. In other words, this method returns all polygons that
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// contain any connected component of the target, along with an arbitrary
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// subset of the polygons that intersect the target.
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//
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// For example, suppose that the index contains two abutting polygons
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// A and B. If the target consists of two points "a" contained by A and
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// "b" contained by B, then both A and B are returned. But if the target
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// consists of the edge "ab", then any subset of {A, B} could be returned
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// (because both polygons intersect the target but neither one contains
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// the edge "ab").
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//
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// If the visit function returns false, this method terminates early and
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// returns false as well. Otherwise returns true.
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//
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// NOTE(roberts): This method exists only for the purpose of implementing
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// edgeQuery IncludeInteriors efficiently.
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visitContainingShapes(index *ShapeIndex, v shapePointVisitorFunc) bool
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}
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// shapePointVisitorFunc defines a type of function the visitContainingShapes can call.
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type shapePointVisitorFunc func(containingShape Shape, targetPoint Point) bool
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