From 4d0f41cc6b13754ff43b42013aaadc4763912e90 Mon Sep 17 00:00:00 2001
From: Thomas Friedel <tomee6@gmail.com>
Date: Wed, 17 Apr 2019 13:01:38 +0200
Subject: [PATCH] more precise rasterization

---
 backend/software/triangles.go | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/backend/software/triangles.go b/backend/software/triangles.go
index cc61680..476ff31 100644
--- a/backend/software/triangles.go
+++ b/backend/software/triangles.go
@@ -19,10 +19,10 @@ func triangleLR(tri [][2]float64, y float64) (l, r float64, outside bool) {
 	}
 
 	// check general bounds
-	if y < a[1] {
+	if y <= a[1] {
 		return a[0], a[0], true
 	}
-	if y >= c[1] {
+	if y > c[1] {
 		return c[0], c[0], true
 	}
 
@@ -73,6 +73,9 @@ func (b *SoftwareBackend) fillTriangle(tri [][2]float64, fn func(x, y int)) {
 		} else if r > float64(b.w) {
 			r = float64(b.w)
 		}
+		if l >= r {
+			continue
+		}
 		fl, cr := int(math.Floor(l)), int(math.Ceil(r))
 		for x := fl; x <= cr; x++ {
 			fx := float64(x) + 0.5
@@ -127,6 +130,9 @@ func (b *SoftwareBackend) fillQuad(quad [4][2]float64, fn func(x, y int, sx, sy
 		} else if r > float64(b.w) {
 			r = float64(b.w)
 		}
+		if l >= r {
+			continue
+		}
 
 		v0 := [2]float64{float64(l) - quad[0][0], float64(y) - quad[0][1]}
 		sx0 := topv[0]*v0[0] + topv[1]*v0[1]