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72 lines
2.8 KiB
Go
72 lines
2.8 KiB
Go
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// Copyright 2014 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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// A Region represents a two-dimensional region on the unit sphere.
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//
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// The purpose of this interface is to allow complex regions to be
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// approximated as simpler regions. The interface is restricted to methods
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// that are useful for computing approximations.
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type Region interface {
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// CapBound returns a bounding spherical cap. This is not guaranteed to be exact.
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CapBound() Cap
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// RectBound returns a bounding latitude-longitude rectangle that contains
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// the region. The bounds are not guaranteed to be tight.
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RectBound() Rect
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// ContainsCell reports whether the region completely contains the given region.
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// It returns false if containment could not be determined.
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ContainsCell(c Cell) bool
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// IntersectsCell reports whether the region intersects the given cell or
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// if intersection could not be determined. It returns false if the region
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// does not intersect.
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IntersectsCell(c Cell) bool
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// ContainsPoint reports whether the region contains the given point or not.
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// The point should be unit length, although some implementations may relax
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// this restriction.
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ContainsPoint(p Point) bool
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// CellUnionBound returns a small collection of CellIDs whose union covers
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// the region. The cells are not sorted, may have redundancies (such as cells
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// that contain other cells), and may cover much more area than necessary.
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//
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// This method is not intended for direct use by client code. Clients
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// should typically use Covering, which has options to control the size and
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// accuracy of the covering. Alternatively, if you want a fast covering and
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// don't care about accuracy, consider calling FastCovering (which returns a
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// cleaned-up version of the covering computed by this method).
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//
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// CellUnionBound implementations should attempt to return a small
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// covering (ideally 4 cells or fewer) that covers the region and can be
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// computed quickly. The result is used by RegionCoverer as a starting
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// point for further refinement.
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CellUnionBound() []CellID
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}
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// Enforce Region interface satisfaction.
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var (
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_ Region = Cap{}
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_ Region = Cell{}
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_ Region = (*CellUnion)(nil)
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_ Region = (*Loop)(nil)
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_ Region = Point{}
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_ Region = (*Polygon)(nil)
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_ Region = (*Polyline)(nil)
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_ Region = Rect{}
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)
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