diff --git a/backend/softwarebackend/color.go b/backend/softwarebackend/color.go
index 50be62c..4e8b16c 100644
--- a/backend/softwarebackend/color.go
+++ b/backend/softwarebackend/color.go
@@ -22,20 +22,22 @@ func mix(src, dest color.Color) color.RGBA {
 	b1 := float64(ib1) / 65535.0
 	a1 := float64(ia1) / 65535.0
 
-	ir2, ig2, ib2, _ := dest.RGBA()
+	ir2, ig2, ib2, ia2 := dest.RGBA()
 	r2 := float64(ir2) / 65535.0
 	g2 := float64(ig2) / 65535.0
 	b2 := float64(ib2) / 65535.0
+	a2 := float64(ia2) / 65535.0
 
 	r := (r1-r2)*a1 + r2
 	g := (g1-g2)*a1 + g2
 	b := (b1-b2)*a1 + b2
+	a := math.Max((a1-a2)*a1+a2, a2)
 
 	return color.RGBA{
 		R: uint8(math.Round(r * 255.0)),
 		G: uint8(math.Round(g * 255.0)),
 		B: uint8(math.Round(b * 255.0)),
-		A: 255,
+		A: uint8(math.Round(a * 255.0)),
 	}
 }
 
diff --git a/backend/softwarebackend/software.go b/backend/softwarebackend/software.go
index 81935c0..e5c2c21 100644
--- a/backend/softwarebackend/software.go
+++ b/backend/softwarebackend/software.go
@@ -10,7 +10,7 @@ import (
 type SoftwareBackend struct {
 	Image *image.RGBA
 
-	// MSAA int
+	MSAA int
 
 	clip *image.Alpha
 	mask *image.Alpha
diff --git a/backend/softwarebackend/triangles.go b/backend/softwarebackend/triangles.go
index 8b1ea76..994e8e0 100644
--- a/backend/softwarebackend/triangles.go
+++ b/backend/softwarebackend/triangles.go
@@ -172,7 +172,7 @@ func (b *SoftwareBackend) fillTriangleMSAA(tri [][2]float64, msaaLevel int, msaa
 				sx := float64(x) + msaaStep*0.5
 				for stepx := 0; stepx <= msaaLevel; stepx++ {
 					if sx >= l[stepy] && sx < r[stepy] {
-						msaaPixels = append(msaaPixels, msaaPixel{ix: x, iy: y, fx: sx, fy: sy})
+						msaaPixels = addMSAAPixel(msaaPixels, msaaPixel{ix: x, iy: y, fx: sx, fy: sy})
 					}
 					sx += msaaStep
 				}
@@ -184,6 +184,15 @@ func (b *SoftwareBackend) fillTriangleMSAA(tri [][2]float64, msaaLevel int, msaa
 	return msaaPixels
 }
 
+func addMSAAPixel(msaaPixels []msaaPixel, px msaaPixel) []msaaPixel {
+	for _, px2 := range msaaPixels {
+		if px == px2 {
+			return msaaPixels
+		}
+	}
+	return append(msaaPixels, px)
+}
+
 func quadArea(quad [4][2]float64) float64 {
 	leftv := [2]float64{quad[1][0] - quad[0][0], quad[1][1] - quad[0][1]}
 	topv := [2]float64{quad[3][0] - quad[0][0], quad[3][1] - quad[0][1]}
@@ -329,10 +338,7 @@ func (b *SoftwareBackend) fillTrianglesMSAA(pts [][2]float64, msaaLevel int, fn
 				continue
 			}
 
-			col := fn(px.fx, px.fy)
-			if col.A == 0 {
-				return
-			}
+			col := fn(px2.fx, px2.fy)
 			mr += int(col.R)
 			mg += int(col.G)
 			mb += int(col.B)
@@ -348,14 +354,13 @@ func (b *SoftwareBackend) fillTrianglesMSAA(pts [][2]float64, msaaLevel int, fn
 			A: uint8(ma / samples),
 		}
 		b.Image.SetRGBA(px.ix, px.iy, mix(combined, b.Image.RGBAAt(px.ix, px.iy)))
-
 	}
 }
 
 func (b *SoftwareBackend) fillTriangles(pts [][2]float64, fn func(x, y float64) color.RGBA) {
-	// if b.MSAA > 0 {
-	// 	b.fillTrianglesMSAA(pts, b.MSAA, fn)
-	// } else {
-	b.fillTrianglesNoAA(pts, fn)
-	// }
+	if b.MSAA > 0 {
+		b.fillTrianglesMSAA(pts, b.MSAA, fn)
+	} else {
+		b.fillTrianglesNoAA(pts, fn)
+	}
 }