Terms like 'physically-based rendering', 'ray-traced distance field', 'distance field ambient occlusion', 'temporal anti-aliasing' might not mean anything to most of us, but those who're studying game physics or 3D animation know what these are. Some of the best looking games in recent times have used the Unreal Engine. This short demo, called 'A Boy and his Kite' has been created by Epic Games, who created Unreal Engine, using the latest Unreal Engine 4. And it ends with a beautiful message about why Unreal Engine is freely available.

And here's a message from Tim Sweeney, the creator of Unreal Engine 4, explaining why it's free.