From: Scott Worley <ScottWorley@ScottWorley.com>
Date: Fri, 21 Dec 2012 15:12:59 +0000 (-0800)
Subject: Helper functions for shapenormals
X-Git-Url: http://git.scottworley.com/nt3d/commitdiff_plain/2d38f7243be5d76cca2812428cc90d0009e672cb

Helper functions for shapenormals
---

diff --git a/nt3d.js b/nt3d.js
index 9b09b09..9c4aeb1 100644
--- a/nt3d.js
+++ b/nt3d.js
@@ -62,6 +62,27 @@ nt3d = {
 		return this.closed_trianglefan([apex].concat(base)).concat(
 		       this.trianglefan(base.reverse()));
 	},
+	shapenormals_from_closed_path: function(path) {
+		return function(i) {
+			var prev = (i == 0) ? path.length-1 : i-1;
+			var next = (i == path.length-1) ? 0 : i+1;
+			return nt3d.sub(path[next], path[prev]);
+		};
+	},
+	shapenormals_from_path_and_extra_points: function(path, first_point, last_point) {
+		return function(i) {
+			var prev = (i == 0) ? first_point : path[i-1];
+			var next = (i == path.length-1) ? last_point : path[i+1];
+			return nt3d.sub(next, prev);
+		};
+	},
+	shapenormals_from_path_and_first_and_last_normals: function(path, first_normal, last_normal) {
+		return function(i) {
+			if (i == 0) { return first_normal; }
+			if (i == path.length-1) { return last_normal; }
+			return nt3d.sub(path[i+1], path[i-1]);
+		};
+	},
 	to_function: function(thing, make_indexer) {
 		// If thing is a point, just yield thing every time.
 		// If thing is a list of points && make_indexer, index into thing.
diff --git a/torus_by_extrude.html b/torus_by_extrude.html
index c95f821..4655519 100644
--- a/torus_by_extrude.html
+++ b/torus_by_extrude.html
@@ -8,7 +8,7 @@
       	return nt3d.closed_extrude(
       	  path,
 	  nt3d.circle(cross_section_radius, short_steps),
-      	  nt3d.rotate_about_origin(path, [0,0,1], Math.PI/2),
+	  nt3d.shapenormals_from_closed_path(path),
 	  [0, 0, 1]);
       }
       var params = [["Torus radus", 100],