From 3e758f3c6b89738f046bdbed318c34ef244dec64 Mon Sep 17 00:00:00 2001
From: Brad Hefta-Gaub <brad@highfidelity.io>
Date: Mon, 28 Sep 2015 09:05:39 -0700
Subject: [PATCH] fix Triangle::getNormal, add normal display to rayPickExample

---
 examples/example/scripts/rayPickExample.js | 34 ++++++++++++++++++++--
 libraries/shared/src/GeometryUtil.cpp      | 12 ++------
 2 files changed, 34 insertions(+), 12 deletions(-)

diff --git a/examples/example/scripts/rayPickExample.js b/examples/example/scripts/rayPickExample.js
index e573226f19..d85138211e 100644
--- a/examples/example/scripts/rayPickExample.js
+++ b/examples/example/scripts/rayPickExample.js
@@ -11,6 +11,17 @@
 //  See the accompanying file LICENSE or http://www.apache.org/licenses/LICENSE-2.0.html
 //
 
+
+var normalDisplay = Entities.addEntity({
+    type: "Line",
+    name: "normalDisplay",
+    visible: false,
+    color: { red: 255, green: 0, blue: 0 },
+    dimensions: { x: 100, y: 100, z: 100 }
+});
+
+var wasVisible = false;
+
 function mouseMoveEvent(event) {
     print("mouseMoveEvent event.x,y=" + event.x + ", " + event.y);
     var pickRay = Camera.computePickRay(event.x, event.y);
@@ -34,12 +45,29 @@ function mouseMoveEvent(event) {
                     + intersection.intersection.y + ", " + intersection.intersection.z);
         print("intersection surfaceNormal.x/y/z=" + intersection.surfaceNormal.x + ", "
                     + intersection.surfaceNormal.y + ", " + intersection.surfaceNormal.z);
+
+
+        // Note: line entity takes points in "entity relative frame"
+        var lineStart = { x: 0, y: 0, z: 0 };
+        var lineEnd = intersection.surfaceNormal;
+
+        Entities.editEntity(normalDisplay, {
+            visible: true,
+            position: intersection.intersection,
+            linePoints: [lineStart, lineEnd],
+        });
+        wasVisible = true;
+    } else {
+        if (wasVisible) {
+            Entities.editEntity(normalDisplay, { visible: false });
+            wasVisible = false;
+        }
     }
 }
 
 Controller.mouseMoveEvent.connect(mouseMoveEvent);
 
-function scriptEnding() {
-}
-Script.scriptEnding.connect(scriptEnding);
+Script.scriptEnding.connect(function() {
+    Entities.deleteEntity(normalDisplay);
+});
 
diff --git a/libraries/shared/src/GeometryUtil.cpp b/libraries/shared/src/GeometryUtil.cpp
index 9d109e5970..96c4d3bdea 100644
--- a/libraries/shared/src/GeometryUtil.cpp
+++ b/libraries/shared/src/GeometryUtil.cpp
@@ -257,15 +257,9 @@ bool findRayCapsuleIntersection(const glm::vec3& origin, const glm::vec3& direct
 
 // reference https://www.opengl.org/wiki/Calculating_a_Surface_Normal
 glm::vec3 Triangle::getNormal() const {
-    glm::vec3 u = v1 - v0;
-    glm::vec3 v = v2 - v0;
-    glm::vec3 result;
-
-    result.x = (u.y * v.z) - (u.z * v.y);
-    result.x = (u.z * v.x) - (u.x * v.z);
-    result.x = (u.x * v.y) - (u.y * v.x);
-
-    return glm::normalize(result);
+    glm::vec3 edge1 = v1 - v0;
+    glm::vec3 edge2 = v2 - v0;
+    return glm::normalize(glm::cross(edge1, edge2));
 }
 
 bool findRayTriangleIntersection(const glm::vec3& origin, const glm::vec3& direction,