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fixed the line intersection calculation; splitting polygons at self-intersections now works

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This commit is contained in:
Thomas Friedel 2018-02-12 10:30:49 +01:00
parent a7c6f10541
commit 31c2eb204e
2 changed files with 33 additions and 17 deletions
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23
paths.go
View file

@ -289,8 +289,8 @@ func (cv *Canvas) lineJoint(p pathPoint, p0, p1, p2, l0p0, l0p1, l0p2, l0p3 lm.V
l1p2 := p2.Add(v3)
l1p3 := p1.Add(v3)
ip0, _ := lineIntersection(l0p0, l0p1, l1p1, l1p0)
ip1, _ := lineIntersection(l0p2, l0p3, l1p3, l1p2)
ip0, _, _ := lineIntersection(l0p0, l0p1, l1p1, l1p0)
ip1, _, _ := lineIntersection(l0p2, l0p3, l1p3, l1p2)
tris = append(tris,
p1[0], p1[1], l0p1[0], l0p1[1], ip0[0], ip0[1],
@ -328,17 +328,22 @@ func (cv *Canvas) addCircleTris(center lm.Vec2, radius float32, tris []float32)
return tris
}
func lineIntersection(a0, a1, b0, b1 lm.Vec2) (lm.Vec2, float32) {
func lineIntersection(a0, a1, b0, b1 lm.Vec2) (lm.Vec2, float32, float32) {
va := a1.Sub(a0)
vb := b1.Sub(b0)
if vb[1] == 0 {
r := (b0[1] + (a0[0]-b0[0])*(vb[1]/vb[0]) - a0[1]) / (va[1] - va[0]*(vb[1]/vb[0]))
return a0.Add(va.MulF(r)), r
if (va[0] == 0 && vb[0] == 0) || (va[1] == 0 && vb[1] == 0) || (va[0] == 0 && va[1] == 0) || (vb[0] == 0 && vb[1] == 0) {
return lm.Vec2{}, float32(math.Inf(1)), float32(math.Inf(1))
}
p := (vb[1]*(a0[0]-b0[0]) - a0[1]*vb[0] + b0[1]*vb[0]) / (va[1]*vb[0] - va[0]*vb[1])
var q float32
if vb[0] == 0 {
q = (a0[1] + p*va[1] - b0[1]) / vb[1]
} else {
q = (a0[0] + p*va[0] - b0[0]) / vb[0]
}
r := (b0[0] + (a0[1]-b0[1])*(vb[0]/vb[1]) - a0[0]) / (va[0] - va[1]*(vb[0]/vb[1]))
return a0.Add(va.MulF(r)), r
return a0.Add(va.MulF(p)), p, q
}
func (cv *Canvas) Fill() {
@ -353,7 +358,7 @@ func (cv *Canvas) Fill() {
if len(path) < 3 {
return
}
//path = cv.cutIntersections(path)
path = cv.cutIntersections(path)
cv.activate()

27
triangulation.go
View file

@ -88,6 +88,7 @@ func triangulatePath(path []pathPoint, target []float32) []float32 {
if !polygonContainsPoint(polygon, center) {
continue triangles
}
break
}
target = append(target, a[0], a[1], b[0], b[1], c[0], c[1])
break
@ -101,6 +102,8 @@ func triangulatePath(path []pathPoint, target []float32) []float32 {
func (cv *Canvas) cutIntersections(path []pathPoint) []pathPoint {
type cut struct {
from, to int
j int
b bool
ratio float32
point lm.Vec2
}
@ -109,26 +112,34 @@ func (cv *Canvas) cutIntersections(path []pathPoint) []pathPoint {
cuts := cutBuf[:0]
for i := 0; i < len(cv.polyPath); i++ {
a0 := cv.polyPath[(i+len(cv.polyPath)-1)%len(cv.polyPath)].pos
ip := (i + len(cv.polyPath) - 1) % len(cv.polyPath)
a0 := cv.polyPath[ip].pos
a1 := cv.polyPath[i].pos
for j := i + 1; j < len(cv.polyPath); j++ {
b0 := cv.polyPath[(j+len(cv.polyPath)-1)%len(cv.polyPath)].pos
jp := (j + len(cv.polyPath) - 1) % len(cv.polyPath)
if ip == j || jp == i {
continue
}
b0 := cv.polyPath[jp].pos
b1 := cv.polyPath[j].pos
p, r := lineIntersection(a0, a1, b0, b1)
if r <= 0 || r >= 1 {
p, r1, r2 := lineIntersection(a0, a1, b0, b1)
if r1 <= 0 || r1 >= 1 || r2 <= 0 || r2 >= 1 {
continue
}
cuts = append(cuts, cut{
from: (i + len(cv.polyPath) - 1) % len(cv.polyPath),
from: ip,
to: i,
ratio: r,
ratio: r1,
point: p,
j: j,
})
cuts = append(cuts, cut{
from: (j + len(cv.polyPath) - 1) % len(cv.polyPath),
from: jp,
to: j,
ratio: p.Sub(b0).Len() / b1.Sub(b0).Len(),
ratio: r2,
point: p,
j: i,
b: true,
})
}
}