69 lines
1.6 KiB
Go
69 lines
1.6 KiB
Go
|
// Copyright © 2016 Abcum Ltd
|
||
|
|
//
|
||
|
|
// 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 geof
|
||
|
|
|
||
|
|
import (
|
||
|
|
"math"
|
||
|
|
|
||
|
|
"github.com/abcum/surreal/sql"
|
||
|
|
)
|
||
|
|
|
||
|
|
func raycast(point, beg, end *sql.Point) bool {
|
||
|
|
|
||
|
|
// Always ensure that the the first point
|
||
|
|
// has a Y coordinate that is less than
|
||
|
|
// the second point. Switch if not.
|
||
|
|
|
||
|
|
if beg.LO > end.LO {
|
||
|
|
beg, end = end, beg
|
||
|
|
}
|
||
|
|
|
||
|
|
// Move the point's Y coordinate outside of
|
||
|
|
// the bounds of the testing region so that
|
||
|
|
// we can start drawing a ray
|
||
|
|
for point.LO == beg.LO || point.LO == end.LO {
|
||
|
|
lng := math.Nextafter(point.LO, math.Inf(1))
|
||
|
|
point = sql.NewPoint(point.LA, lng)
|
||
|
|
}
|
||
|
|
|
||
|
|
// If we are outside of the polygon, indicate so.
|
||
|
|
if point.LO < beg.LO || point.LO > end.LO {
|
||
|
|
return false
|
||
|
|
}
|
||
|
|
|
||
|
|
if beg.LA > end.LA {
|
||
|
|
if point.LA > beg.LA {
|
||
|
|
return false
|
||
|
|
}
|
||
|
|
if point.LA < end.LA {
|
||
|
|
return true
|
||
|
|
}
|
||
|
|
|
||
|
|
} else {
|
||
|
|
if point.LA > end.LA {
|
||
|
|
return false
|
||
|
|
}
|
||
|
|
if point.LA < beg.LA {
|
||
|
|
return true
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
raySlope := (point.LO - beg.LO) / (point.LA - beg.LA)
|
||
|
|
diagSlope := (end.LO - beg.LO) / (end.LA - beg.LA)
|
||
|
|
|
||
|
|
return raySlope >= diagSlope
|
||
|
|
|
||
|
|
}
|