64 lines
2.1 KiB
Go
64 lines
2.1 KiB
Go
|
// Copyright 2017 Google Inc. All rights reserved.
|
||
|
|
//
|
||
|
|
// Licensed under the Apache License, Version 2.0 (the "License");
|
||
|
|
// you may not use this file except in compliance with the License.
|
||
|
|
// You may obtain a copy of the License at
|
||
|
|
//
|
||
|
|
// http://www.apache.org/licenses/LICENSE-2.0
|
||
|
|
//
|
||
|
|
// Unless required by applicable law or agreed to in writing, software
|
||
|
|
// distributed under the License is distributed on an "AS IS" BASIS,
|
||
|
|
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
||
|
|
// See the License for the specific language governing permissions and
|
||
|
|
// limitations under the License.
|
||
|
|
|
||
|
|
package s2
|
||
|
|
|
||
|
|
// ContainsVertexQuery is used to track the edges entering and leaving the
|
||
|
|
// given vertex of a Polygon in order to be able to determine if the point is
|
||
|
|
// contained by the Polygon.
|
||
|
|
//
|
||
|
|
// Point containment is defined according to the semi-open boundary model
|
||
|
|
// which means that if several polygons tile the region around a vertex,
|
||
|
|
// then exactly one of those polygons contains that vertex.
|
||
|
|
type ContainsVertexQuery struct {
|
||
|
|
target Point
|
||
|
|
edgeMap map[Point]int
|
||
|
|
}
|
||
|
|
|
||
|
|
// NewContainsVertexQuery returns a new query for the given vertex whose
|
||
|
|
// containment will be determined.
|
||
|
|
func NewContainsVertexQuery(target Point) *ContainsVertexQuery {
|
||
|
|
return &ContainsVertexQuery{
|
||
|
|
target: target,
|
||
|
|
edgeMap: make(map[Point]int),
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
// AddEdge adds the edge between target and v with the given direction.
|
||
|
|
// (+1 = outgoing, -1 = incoming, 0 = degenerate).
|
||
|
|
func (q *ContainsVertexQuery) AddEdge(v Point, direction int) {
|
||
|
|
q.edgeMap[v] += direction
|
||
|
|
}
|
||
|
|
|
||
|
|
// ContainsVertex reports a +1 if the target vertex is contained, -1 if it is
|
||
|
|
// not contained, and 0 if the incident edges consisted of matched sibling pairs.
|
||
|
|
func (q *ContainsVertexQuery) ContainsVertex() int {
|
||
|
|
// Find the unmatched edge that is immediately clockwise from Ortho(P).
|
||
|
|
referenceDir := Point{q.target.Ortho()}
|
||
|
|
|
||
|
|
bestPoint := referenceDir
|
||
|
|
bestDir := 0
|
||
|
|
|
||
|
|
for k, v := range q.edgeMap {
|
||
|
|
if v == 0 {
|
||
|
|
continue // This is a "matched" edge.
|
||
|
|
}
|
||
|
|
if OrderedCCW(referenceDir, bestPoint, k, q.target) {
|
||
|
|
bestPoint = k
|
||
|
|
bestDir = v
|
||
|
|
}
|
||
|
|
}
|
||
|
|
return bestDir
|
||
|
|
}
|