--- a/cmd/tin2octree/vertex.go	Wed Sep 19 10:50:47 2018 +0200
+++ b/cmd/tin2octree/vertex.go	Wed Sep 19 10:52:20 2018 +0200
@@ -1,7 +1,5 @@
 package main
 
-import "math"
-
 type vertex struct {
 	x float64
 	y float64
@@ -32,66 +30,6 @@
 	}
 }
 
-type plane struct {
-	a float64
-	b float64
-	c float64
-	d float64
-}
-
-func (a vertex) cross(b vertex) vertex {
-	return vertex{
-		a.y*b.z - a.z*b.y,
-		a.z*b.x - a.x*b.z,
-		a.x*b.y - a.y*b.x,
-	}
-}
-
-func (a vertex) sub(b vertex) vertex {
-	return vertex{
-		a.x - b.x,
-		a.y - b.y,
-		a.z - b.z,
-	}
-}
-
-func (a vertex) scale(s float64) vertex {
-	return vertex{
-		s * a.x,
-		s * a.y,
-		s * a.z,
-	}
-}
-
-func (a vertex) dot(b vertex) float64 {
-	return a.x*b.x + a.y*b.y + a.z*b.z
-}
-
-func (a vertex) length() float64 {
-	return math.Sqrt(a.x*a.x + a.y*a.y + a.z*a.z)
-}
-
-func newPlane(v1, v2, v3 vertex) plane {
-	w1 := v2.sub(v1)
-	w2 := v3.sub(v1)
-	p := w1.cross(w2)
-	p = p.scale(1 / p.length())
-
-	// x*p.x + y*p.y + z*p.z + d = 0
-	// d = -(x*p.x + y*p.y + z*p.z)
-	d := -p.dot(v1)
-	return plane{
-		a: p.x,
-		b: p.y,
-		c: p.z,
-		d: d,
-	}
-}
-
-func (p plane) eval(v vertex) float64 {
-	return p.a*v.x + p.b*v.y + p.c*v.z + p.d
-}
-
 func interpolate(v1, v2 vertex) func(vertex) vertex {
 	return func(s vertex) vertex {
 		return vertex{