Add SphereShape.cpp to project

libraries/shared/src/SphereShape.cpp

@@ -0,0 +1,44 @@
+//
+//  SphereShape.cpp
+//  libraries/shared/src
+//
+//  Created by Andrew Meadows on 2014.06.17
+//  Copyright 2014 High Fidelity, Inc.
+//
+//  Distributed under the Apache License, Version 2.0.
+//  See the accompanying file LICENSE or http://www.apache.org/licenses/LICENSE-2.0.html
+//
+
+#include <glm/gtx/norm.hpp>
+
+#include "SphereShape.h"
+
+bool SphereShape::findRayIntersection(const glm::vec3& rayStart, const glm::vec3& rayDirection, float& distance) const {
+    float r2 = _boundingRadius * _boundingRadius;
+
+    // compute closest approach (CA)
+    float a = glm::dot(_position - rayStart, rayDirection); // a = distance from ray-start to CA
+    float b2 = glm::distance2(_position, rayStart + a * rayDirection); // b2 = squared distance from sphere-center to CA
+    if (b2 > r2) {
+        // ray does not hit sphere
+        return false;
+    }
+    float c = sqrtf(r2 - b2); // c = distance from CA to sphere surface along rayDirection
+    float d2 = glm::distance2(rayStart, _position); // d2 = squared distance from sphere-center to ray-start
+    if (a < 0.0f) {
+        // ray points away from sphere-center
+        if (d2 > r2) {
+            // ray starts outside sphere
+            return false;
+        }
+        // ray starts inside sphere
+        distance = c + a;
+    } else if (d2 > r2) {
+        // ray starts outside sphere
+        distance = a - c;
+    } else {
+        // ray starts inside sphere
+        distance = a + c;
+    }
+    return true;
+}