Fix line issues

tinyrender1/main.go

@@ -44,9 +44,9 @@ func main() {
 
 	// Just draw a simple line (a million times or something)
 	for range LineRepeat {
-		LineDumb3(&fb, 0xFFFFFF, 100, 100, 350, 200)
-		LineDumb3(&fb, 0xFF0000, 120, 100, 200, 350)
-		LineDumb3(&fb, 0xFF0000, 350, 200, 100, 100) // backward first line
+		LineDumb4(&fb, 0xFFFFFF, 100, 100, 350, 200)
+		LineDumb4(&fb, 0xFF0000, 120, 100, 200, 350)
+		LineDumb4(&fb, 0xFF0000, 350, 200, 100, 100) // backward first line
 	}
 
 	log.Printf("Exporting ppm to stdout")

tinyrender1/render.go

@@ -50,3 +50,45 @@ func LineDumb3(fb *Framebuffer, color uint, x0 int, y0 int, x1 int, y1 int) {
 		}
 	}
 }
+
+func LineDumb4(fb *Framebuffer, color uint, x0 int, y0 int, x1 int, y1 int) {
+	steep := false
+	// This one makes sure that going pixel by pixel will not make holes in the
+	// other direction by always moving in the less steep direction.
+	if math.Abs(float64(x1-x0)) < math.Abs(float64(y1-y0)) {
+		x0, y0 = y0, x0
+		x1, y1 = y1, x1
+		steep = true
+	}
+	// Don't let lines be invisible, always go left to right
+	if x0 > x1 { // need to be left to right
+		x0, x1 = x1, x0
+		y0, y1 = y1, y0 // Why are we swapping these? I guess because we're swapping the points...
+	}
+	dx := x1 - x0 // These MUST be POST calcs
+	dy := y1 - y0
+	// Delta error or something? Basically, as we move in one direction, we get farther
+	// and farther off course if we never move in the OTHER direction. This is the amount
+	// of that per x direction.
+	derror := math.Abs(float64(dy) / float64(dx))
+	y := uint(y0)
+	var err float64
+	// Same as dumb2, going across pixel by pixel. But "x" here might actually be y
+	// because of the inverted direction
+	for x := x0; x <= x1; x++ {
+		if steep {
+			fb.Set(y, uint(x), color)
+		} else {
+			fb.Set(uint(x), y, color)
+		}
+		err += derror
+		if err > 0.5 {
+			if y1 > y0 {
+				y += 1
+			} else {
+				y = y - 1
+			}
+			err -= 1
+		}
+	}
+}

tinyrender1/run.sh

@@ -1,6 +1,11 @@
 #!/bin/sh
 
+if [ $# -ne 1 ]; then
+  echo "You must pass the basename for the .prof and .ppm"
+  exit 1
+fi
+
 echo "Building"
 go build
 echo "Running"
-./tinyrender1 "$@" > image.ppm
+./tinyrender1 "-cpuprofile=$1.prof" >"$1.ppm"