From 6e5e17591a2a5adac5e4ec016c7bad71505b1e64 Mon Sep 17 00:00:00 2001
From: Scott Worley <ScottWorley@ScottWorley.com>
Date: Sat, 29 Dec 2012 00:08:19 -0800
Subject: [PATCH] Remove degenerate faces

---
 nt3d.js | 31 ++++++++++++++++++++++++++++---
 1 file changed, 28 insertions(+), 3 deletions(-)

diff --git a/nt3d.js b/nt3d.js
index 33e271b..3ce05be 100644
--- a/nt3d.js
+++ b/nt3d.js
@@ -297,6 +297,17 @@ nt3d = {
 				angle),
 			center);
 	},
+	point_equal: function(a, b, epsilon) {
+		return Math.abs(a[0] - b[0]) < epsilon &&
+		       Math.abs(a[1] - b[1]) < epsilon &&
+		       Math.abs(a[2] - b[2]) < epsilon;
+	},
+	degenerate_face_epsilon: 1e-10,
+	is_degenerate: function(a, b, c) {
+		return this.point_equal(a, b, this.degenerate_face_epsilon) ||
+		       this.point_equal(b, c, this.degenerate_face_epsilon) ||
+		       this.point_equal(c, a, this.degenerate_face_epsilon);
+	},
 	go: function() {
 		// Remove any previous download links
 		var old_download_link = document.getElementById("nt3d_download");
@@ -323,11 +334,10 @@ nt3d = {
 		if (this.points.length % 3 != 0) {
 			alert("Points list length not divisble by 3!");
 		}
-		var n = this.points.length / 3;
 		var nan_count = 0;
 		var nan_point_count = 0;
 		var nan_face_count = 0;
-		for (var i = 0; i < n; i++) {
+		for (var i = 0; i < this.points.length/3; i++) {
 			var nan_in_face = false;
 			for (var j = 0; j < 3; j++) {
 				var nan_in_point = false;
@@ -346,9 +356,24 @@ nt3d = {
 			alert(nan_count + " NaNs in " + nan_point_count + " points in " + nan_face_count + " faces.");
 		}
 
+		// Remove degenerate faces
+		var degenerate_face_count = 0;
+		for (var i = 0; i < this.points.length/3; i++) {
+			if (this.is_degenerate(this.points[i*3+0], 
+			                       this.points[i*3+1], 
+			                       this.points[i*3+2])) {
+				this.points.splice(i*3, 3);
+				i--;
+				degenerate_face_count ++;
+			}
+		}
+		if (degenerate_face_count != 0) {
+			console.log("Removed " + degenerate_face_count + " degenerate faces");
+		}
+
 		// Make STL
 		this.stl = "solid " + this.user_function.name + "\n";
-		for (var i = 0; i < n; i++) {
+		for (var i = 0; i < this.points.length/3; i++) {
 			var a = this.points[i*3+0];
 			var b = this.points[i*3+1];
 			var c = this.points[i*3+2];
-- 
2.44.1