1 files changed, 54 insertions, 0 deletions
diff --git a/dep/g3dlite/source/Cone.cpp b/dep/g3dlite/source/Cone.cpp
index 3104b8424a7..586ccfd6761 100644
--- a/dep/g3dlite/source/Cone.cpp
+++ b/dep/g3dlite/source/Cone.cpp
@@ -17,6 +17,24 @@
 
 namespace G3D {
 
+
+float Cone::solidAngleFromHalfAngle(float halfAngle){
+    return 2.0f * pif() * (1 - cosf(halfAngle));
+}
+
+double Cone::solidAngleFromHalfAngle(double halfAngle){
+    return 2.0 * pi() * (1.0 - cos(halfAngle));
+}
+
+float Cone::halfAngleFromSolidAngle(float solidAngle){
+    return acos((1.0f - (solidAngle / (2.0f * pif()))));
+}
+
+double Cone::halfAngleFromSolidAngle(double solidAngle){
+    return aCos((1.0 - (solidAngle / (2.0 * pi()))));
+}
+
+
 Cone::Cone(const Vector3 &tip, const Vector3 &direction, float angle) {
     this->tip = tip;
     this->direction = direction.direction();
@@ -26,6 +44,42 @@ Cone::Cone(const Vector3 &tip, const Vector3 &direction, float angle) {
     debugAssert(angle <= pi());
 }
 
+Vector3 Cone::randomDirectionInCone(Random& rng) const {
+        const float cosThresh = cos(angle);
+
+        float cosAngle;
+        float normalizer;
+        Vector3 v;
+        do {
+            float vlenSquared;
+
+            // Sample uniformly on a sphere by rejection sampling and then normalizing
+            do {
+                v.x = rng.uniform(-1, 1);
+                v.y = rng.uniform(-1, 1);
+                v.z = rng.uniform(-1, 1);
+
+                // Sample uniformly on a cube
+                vlenSquared = v.squaredLength();
+            } while (vlenSquared > 1);
+
+
+            const float temp = v.dot(direction);
+        
+            // Compute 1 / ||v||, but
+            // if the vector is in the wrong hemisphere, flip the sign
+            normalizer = rsqrt(vlenSquared) * sign(temp);
+
+            // Cosine of the angle between v and the light's negative-z axis
+            cosAngle = temp * normalizer;
+
+        } while (cosAngle < cosThresh);
+
+        // v was within the cone.  Normalize it and maybe flip the hemisphere.
+        return v * normalizer;
+    }
+
+
 /**
  Forms the smallest cone that contains the box.  Undefined if
  the tip is inside or on the box.