-
Notifications
You must be signed in to change notification settings - Fork 41
/
triangulation.go
170 lines (156 loc) · 3.37 KB
/
triangulation.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
package canvas
import (
"math"
"sort"
)
func pointIsRightOfLine(a, b, p vec) bool {
if a[1] == b[1] {
return false
}
if a[1] > b[1] {
a, b = b, a
}
if p[1] < a[1] || p[1] > b[1] {
return false
}
v := b.sub(a)
r := (p[1] - a[1]) / v[1]
x := a[0] + r*v[0]
return p[0] > x
}
func triangleContainsPoint(a, b, c, p vec) bool {
// if point is outside triangle bounds, return false
if p[0] < a[0] && p[0] < b[0] && p[0] < c[0] {
return false
}
if p[0] > a[0] && p[0] > b[0] && p[0] > c[0] {
return false
}
if p[1] < a[1] && p[1] < b[1] && p[1] < c[1] {
return false
}
if p[1] > a[1] && p[1] > b[1] && p[1] > c[1] {
return false
}
// check whether the point is to the right of each triangle line.
// if the total is 1, it is inside the triangle
count := 0
if pointIsRightOfLine(a, b, p) {
count++
}
if pointIsRightOfLine(b, c, p) {
count++
}
if pointIsRightOfLine(c, a, p) {
count++
}
return count == 1
}
func polygonContainsPoint(polygon []vec, p vec) bool {
a := polygon[len(polygon)-1]
count := 0
for _, b := range polygon {
if pointIsRightOfLine(a, b, p) {
count++
}
a = b
}
return count%2 == 1
}
func triangulatePath(path []pathPoint, target []float32) []float32 {
var buf [500]vec
polygon := buf[:0]
for _, p := range path {
polygon = append(polygon, p.tf)
}
for len(polygon) > 2 {
var i int
triangles:
for i = range polygon {
ib := (i + 1) % len(polygon)
ic := (i + 2) % len(polygon)
a := polygon[i]
b := polygon[ib]
c := polygon[ic]
if isSamePoint(a, c, math.SmallestNonzeroFloat64) {
break
}
for i2, p := range polygon {
if i2 == i || i2 == ib || i2 == ic {
continue
}
if triangleContainsPoint(a, b, c, p) {
continue triangles
}
center := a.add(b).add(c).divf(3)
if !polygonContainsPoint(polygon, center) {
continue triangles
}
}
target = append(target, float32(a[0]), float32(a[1]), float32(b[0]), float32(b[1]), float32(c[0]), float32(c[1]))
break
}
remove := (i + 1) % len(polygon)
polygon = append(polygon[:remove], polygon[remove+1:]...)
}
return target
}
func (cv *Canvas) cutIntersections(path []pathPoint) []pathPoint {
type cut struct {
from, to int
j int
b bool
ratio float64
point vec
}
var cutBuf [50]cut
cuts := cutBuf[:0]
for i := 0; i < len(path); i++ {
ip := (i + len(path) - 1) % len(path)
a0 := path[ip].pos
a1 := path[i].pos
for j := i + 1; j < len(path); j++ {
jp := (j + len(path) - 1) % len(path)
if ip == j || jp == i {
continue
}
b0 := path[jp].pos
b1 := path[j].pos
p, r1, r2 := lineIntersection(a0, a1, b0, b1)
if r1 <= 0 || r1 >= 1 || r2 <= 0 || r2 >= 1 {
continue
}
cuts = append(cuts, cut{
from: ip,
to: i,
ratio: r1,
point: p,
j: j,
})
cuts = append(cuts, cut{
from: jp,
to: j,
ratio: r2,
point: p,
j: i,
b: true,
})
}
}
if len(cuts) == 0 {
return path
}
sort.Slice(cuts, func(i, j int) bool {
a, b := cuts[i], cuts[j]
return a.to > b.to || (a.to == b.to && a.ratio > b.ratio)
})
newPath := make([]pathPoint, len(path)+len(cuts))
copy(newPath[:len(path)], path)
for _, cut := range cuts {
copy(newPath[cut.to+1:], newPath[cut.to:])
newPath[cut.to].next = newPath[cut.to+1].tf
newPath[cut.to].pos = cut.point
newPath[cut.to].tf = cv.tf(cut.point)
}
return newPath
}