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added miter joints for stroked paths

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This commit is contained in:
Thomas Friedel 2018-01-31 16:50:36 +01:00
parent 20674e7f7a
commit a8db8886c7
2 changed files with 80 additions and 13 deletions
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6
canvas.go
View file

@ -25,8 +25,10 @@ type Canvas struct {
}
type pathPoint struct {
pos lm.Vec2
move bool
pos lm.Vec2
move bool
next lm.Vec2
attach bool
}
type drawState struct {

87
paths.go
View file

@ -20,6 +20,12 @@ func (cv *Canvas) MoveTo(x, y float32) {
}
func (cv *Canvas) LineTo(x, y float32) {
if len(cv.path) == 0 {
cv.MoveTo(x, y)
return
}
cv.path[len(cv.path)-1].next = lm.Vec2{x, y}
cv.path[len(cv.path)-1].attach = true
cv.path = append(cv.path, pathPoint{pos: lm.Vec2{x, y}, move: false})
}
@ -48,10 +54,12 @@ func (cv *Canvas) Arc(x, y, radius, startAngle, endAngle float32, anticlockwise
}
func (cv *Canvas) ClosePath() {
if len(cv.path) == 0 {
if len(cv.path) < 2 {
return
}
cv.path = append(cv.path, pathPoint{pos: cv.path[0].pos, move: false})
cv.path[len(cv.path)-1].next = cv.path[0].pos
cv.path[len(cv.path)-1].attach = true
cv.path = append(cv.path, pathPoint{pos: cv.path[0].pos, move: false, next: cv.path[1].pos, attach: true})
}
func (cv *Canvas) Stroke() {
@ -77,7 +85,8 @@ func (cv *Canvas) Stroke() {
var buf [1000]float32
tris := buf[:0]
tris = append(tris, -1, -1, -1, 1, 1, 1, -1, -1, 1, 1, 1, -1)
p0 := cv.path[0].pos
var p0 lm.Vec2
for _, p := range cv.path {
if p.move {
p0 = p.pos
@ -85,16 +94,59 @@ func (cv *Canvas) Stroke() {
}
p1 := p.pos
v1 := p1.Sub(p0).Norm()
v2 := lm.Vec2{v1[1], -v1[0]}.MulF(cv.state.stroke.lineWidth * 0.5)
v1 = v1.MulF(cv.state.stroke.lineWidth * 0.5)
v0 := p1.Sub(p0).Norm()
v1 := lm.Vec2{v0[1], -v0[0]}.MulF(cv.state.stroke.lineWidth * 0.5)
//v0 = v0.MulF(cv.state.stroke.lineWidth * 0.5)
x0f, y0f := cv.vecToGL(p0.Sub(v1).Add(v2))
x1f, y1f := cv.vecToGL(p1.Add(v1).Add(v2))
x2f, y2f := cv.vecToGL(p1.Add(v1).Sub(v2))
x3f, y3f := cv.vecToGL(p0.Sub(v1).Sub(v2))
l0p0 := p0.Add(v1)
l0p1 := p1.Add(v1)
l0p2 := p0.Sub(v1)
l0p3 := p1.Sub(v1)
tris = append(tris, x0f, y0f, x1f, y1f, x2f, y2f, x0f, y0f, x2f, y2f, x3f, y3f)
l0x0f, l0y0f := cv.vecToGL(l0p0)
l0x1f, l0y1f := cv.vecToGL(l0p1)
l0x2f, l0y2f := cv.vecToGL(l0p2)
l0x3f, l0y3f := cv.vecToGL(l0p3)
tris = append(tris,
l0x0f, l0y0f, l0x1f, l0y1f, l0x3f, l0y3f,
l0x0f, l0y0f, l0x3f, l0y3f, l0x2f, l0y2f)
// miter joints
if p.attach {
p2 := p.next
v2 := p1.Sub(p2).Norm()
v3 := lm.Vec2{v2[1], -v2[0]}.MulF(cv.state.stroke.lineWidth * 0.5)
//v2 = v2.MulF(cv.state.stroke.lineWidth * 0.5)
l1p0 := p2.Sub(v3)
l1p1 := p1.Sub(v3)
l1p2 := p2.Add(v3)
l1p3 := p1.Add(v3)
l1x1f, l1y1f := cv.vecToGL(l1p1)
l1x3f, l1y3f := cv.vecToGL(l1p3)
ip0 := lineIntersection(l0p0, l0p1, l1p1, l1p0)
ip1 := lineIntersection(l0p2, l0p3, l1p3, l1p2)
ix0f, iy0f := cv.vecToGL(ip0)
ix1f, iy1f := cv.vecToGL(ip1)
tris = append(tris,
l0x1f, l0y1f, ix0f, iy0f, l1x1f, l1y1f,
l0x1f, l0y1f, l1x1f, l1y1f, l1x3f, l1y3f,
l0x1f, l0y1f, l1x3f, l1y3f, ix1f, iy1f,
l0x1f, l0y1f, ix1f, iy1f, l0x3f, l0y3f)
// todo this is an ugly hack...
tris = append(tris,
l0x1f, l0y1f, ix0f, iy0f, l1x1f, l1y1f,
l0x1f, l0y1f, l1x1f, l1y1f, l0x3f, l0y3f,
l0x1f, l0y1f, l0x3f, l0y3f, ix1f, iy1f,
l0x1f, l0y1f, ix1f, iy1f, l1x3f, l1y3f)
}
p0 = p1
}
@ -117,6 +169,19 @@ func (cv *Canvas) Stroke() {
gli.StencilFunc(gl_EQUAL, 0, 0xFF)
}
func lineIntersection(a0, a1, b0, b1 lm.Vec2) lm.Vec2 {
va := a1.Sub(a0)
vb := b1.Sub(b0)
if vb[1] == 0 {
q := (a0[0] + (b0[1]-a0[1])*(va[0]/va[1]) - b0[0]) / (vb[0] - vb[1]*(va[0]/va[1]))
return b0.Add(vb.MulF(q))
}
p := (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(p))
}
func (cv *Canvas) Fill() {
lastMove := 0
for i, p := range cv.path {