Line drawing

.gitignore

@@ -4,4 +4,5 @@
 *.gif
 *.jpg
 *.jpeg
+*.prof
 a.out

tinyrender1/main.go

@@ -11,6 +11,7 @@ import (
 const (
 	Width      = 512
 	Height     = 512
+	LineRepeat = 1_000_000
 )
 
 func must(err error) {
@@ -41,10 +42,12 @@ func main() {
 
 	log.Printf("Running render")
 
-	// Just draw a simple line
+	// Just draw a simple line (a million times or something)
-	LineDumb(&fb, 0xFFFFFF, 100, 100, 350, 200)
+	for range LineRepeat {
-	LineDumb2(&fb, 0xFF0000, 120, 100, 200, 350)
+		LineDumb3(&fb, 0xFFFFFF, 100, 100, 350, 200)
-	LineDumb2(&fb, 0xFF0000, 350, 200, 100, 100) // backward first line
+		LineDumb3(&fb, 0xFF0000, 120, 100, 200, 350)
+		LineDumb3(&fb, 0xFF0000, 350, 200, 100, 100) // backward first line
+	}
 
 	log.Printf("Exporting ppm to stdout")
 	fmt.Print(fb.ExportPPM())

tinyrender1/render.go

@@ -1,5 +1,9 @@
 package main
 
+import (
+	"math"
+)
+
 // Draw a line using dumb
 func LineDumb(fb *Framebuffer, color uint, x0 uint, y0 uint, x1 uint, y1 uint) {
 	var t float32
@@ -19,3 +23,30 @@ func LineDumb2(fb *Framebuffer, color uint, x0 uint, y0 uint, x1 uint, y1 uint)
 		fb.Set(x, y, color)
 	}
 }
+
+func LineDumb3(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(x0-x1)) < math.Abs(float64(y0-y1)) {
+		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...
+	}
+	// 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++ {
+		t := float32(x-x0) / float32(x1-x0)
+		y := uint(float32(y0)*(1-t) + float32(y1)*t)
+		if steep {
+			fb.Set(y, uint(x), color)
+		} else {
+			fb.Set(uint(x), y, color)
+		}
+	}
+}

tinyrender1/run.sh

@@ -1,3 +1,6 @@
 #!/bin/sh
 
-go build && ./tinyrender1 >image.ppm
+echo "Building"
+go build
+echo "Running"
+./tinyrender1 "$@" > image.ppm