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more accurate rasterizing

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This commit is contained in:
Thomas Friedel 2019-04-16 17:25:48 +02:00
parent d1d2186a2f
commit 973e410204
2 changed files with 36 additions and 23 deletions
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5
backend/software/fill.go
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@ -30,17 +30,16 @@ func (b *SoftwareBackend) Fill(style *backendbase.FillStyle, pts [][2]float64) {
}
func mix(col color.Color, alpha color.Alpha) color.RGBA {
ir, ig, ib, ia := col.RGBA()
ir, ig, ib, _ := col.RGBA()
a2 := float64(alpha.A) / 255.0
r := float64(ir) * a2 / 65535.0
g := float64(ig) * a2 / 65535.0
b := float64(ib) * a2 / 65535.0
a := float64(ia) * a2 / 65535.0
return color.RGBA{
R: uint8(r * 255.0),
G: uint8(g * 255.0),
B: uint8(b * 255.0),
A: uint8(a * 255.0),
A: 255,
}
}

54
backend/software/triangles.go
View file

@ -4,7 +4,7 @@ import (
"math"
)
func triangleLR(tri [][2]float64, y float64) (l, r float64) {
func triangleLR(tri [][2]float64, y float64) (l, r float64, outside bool) {
a, b, c := tri[0], tri[1], tri[2]
// sort by y
@ -20,14 +20,14 @@ func triangleLR(tri [][2]float64, y float64) (l, r float64) {
// check general bounds
if y < a[1] {
return a[0], a[0]
return a[0], a[0], true
}
if y > c[1] {
return c[0], c[0]
if y >= c[1] {
return c[0], c[0], true
}
// find left and right x at y
if y >= a[1] && y <= b[1] {
if y >= a[1] && y <= b[1] && a[1] < b[1] {
r0 := (y - a[1]) / (b[1] - a[1])
l = (b[0]-a[0])*r0 + a[0]
r1 := (y - a[1]) / (c[1] - a[1])
@ -59,20 +59,26 @@ func (b *SoftwareBackend) fillTriangle(tri [][2]float64, fn func(x, y int)) {
maxY = b.h - 1
}
for y := minY; y <= maxY; y++ {
lf, rf := triangleLR(tri, float64(y)+0.5)
l := int(math.Floor(lf))
r := int(math.Ceil(rf))
l, r, out := triangleLR(tri, float64(y)+0.5)
if out {
continue
}
if l < 0 {
l = 0
} else if l >= b.w {
} else if l > float64(b.w) {
continue
}
if r < 0 {
continue
} else if r >= b.w {
r = b.w - 1
} else if r > float64(b.w) {
r = float64(b.w)
}
fl, cr := int(math.Floor(l)), int(math.Ceil(r))
for x := fl; x <= cr; x++ {
fx := float64(x) + 0.5
if fx < l || fx >= r {
continue
}
for x := l; x <= r; x++ {
fn(x, y)
}
}
@ -104,19 +110,22 @@ func (b *SoftwareBackend) fillQuad(quad [4][2]float64, fn func(x, y int, sx, sy
tri1 := [3][2]float64{quad[0], quad[1], quad[2]}
tri2 := [3][2]float64{quad[0], quad[2], quad[3]}
for y := minY; y <= maxY; y++ {
lf1, rf1 := triangleLR(tri1[:], float64(y)+0.5)
lf2, rf2 := triangleLR(tri2[:], float64(y)+0.5)
l := int(math.Floor(math.Min(lf1, lf2)))
r := int(math.Ceil(math.Max(rf1, rf2)))
lf1, rf1, out1 := triangleLR(tri1[:], float64(y)+0.5)
lf2, rf2, out2 := triangleLR(tri2[:], float64(y)+0.5)
if out1 && out2 {
continue
}
l := math.Min(lf1, lf2)
r := math.Max(rf1, rf2)
if l < 0 {
l = 0
} else if l >= b.w {
} else if l > float64(b.w) {
continue
}
if r < 0 {
continue
} else if r >= b.w {
r = b.w - 1
} else if r > float64(b.w) {
r = float64(b.w)
}
v0 := [2]float64{float64(l) - quad[0][0], float64(y) - quad[0][1]}
@ -131,7 +140,12 @@ func (b *SoftwareBackend) fillQuad(quad [4][2]float64, fn func(x, y int, sx, sy
sxStep := (sx1 - sx0) / float64(r-l) / topLen
syStep := (sy1 - sy0) / float64(r-l) / leftLen
for x := l; x <= r; x++ {
fl, cr := int(math.Floor(l)), int(math.Ceil(r))
for x := fl; x <= cr; x++ {
fx := float64(x) + 0.5
if fx < l || fx >= r {
continue
}
fn(x, y, sx, sy)
sx += sxStep
sy += syStep