Adding ViroKit. Needs AWSCore :(

mobile/ios/ViroKit.framework/Headers/VROBillboardConstraint.h

@@ -0,0 +1,40 @@
+//
+//  VROBillboardConstraint.h
+//  ViroRenderer
+//
+//  Created by Raj Advani on 3/9/16.
+//  Copyright © 2016 Viro Media. All rights reserved.
+//
+
+#ifndef VROBillboardConstraint_h
+#define VROBillboardConstraint_h
+
+#include "VROConstraint.h"
+
+enum class VROBillboardAxis {
+    X,
+    Y,
+    Z,
+    All
+};
+
+class VROBillboardConstraint : public VROConstraint {
+    
+public:
+    
+    VROBillboardConstraint(VROBillboardAxis freeAxis) :
+        _freeAxis(freeAxis) {}
+    
+    VROMatrix4f getTransform(const VRORenderContext &context,
+                                     VROMatrix4f transform);
+
+private:
+    
+    VROBillboardAxis _freeAxis;
+    
+    VROQuaternion computeAxisRotation(VROVector3f lookAt, VROVector3f defaultAxis,
+                                      VROVector3f objToCamProj);
+    
+};
+
+#endif /* VROBillboardConstraint_h */