[MUSIC] In this video, we're going to discuss challenges of creating realistic and believable animations in VR. This is a nice looking computer-generated environment. But it would not feel so real if everything just stayed still. You would expect to see the leaves on the tree moving because of wind, the birds on the house flying, and the sun either setting or rising. So it would get darker or brighter soon. None of this is too difficult to animate. This image, on the other hand, would actually be quite hard to animate, the main problem being the cape he's wearing. In order to get a cape looking anywhere close to a real cape, there needs to be a lot of programming and computation. The good news is that most game engines nowadays come with a built-in physics engine that takes care of physical simulations of this kind, so you can just play with the parameters until you are happy with the effect. The physics engine will animate the clothes automatically in a optimized way. Another powerful animation tool that often comes as part of a game engine is called a particle system. It often used to generate effects, such as smoke, fire, and snow. However, the really difficult thing to animate is Superman, or any other 3-D virtual characters in VR. There are a lot of things you need to get right when you implement a virtual character. As human beings ourselves, we all are very critical observers of those virtual characters. So if there is anything that goes slightly wrong, we will instantly spot it. Here is an example, as you can see. This may not be strictly defined as VR, because we used a big projector instead of a VR display. But I like to use this example to show you how the animation was implemented. The body movement of this avatar was animated with motion capture data from a real actress. Here we didn't put any facial expressions on her face, so she looks a bit cold. But often when it comes to character animation, it is better not to include something, rather than having something obviously be wrong. We also programmed her to be interactive, so that when the user moves, the avatar rotates her head towards that direction, to give the impression that she is looking at them. You can do more sophisticated things, but again, if you can't get something quite right, maybe it's best not to do it. A lot of the challenges in creating believable virtual character's animations in VR overlap with the ability of users to interact with them. So we will talk a bit more about programming interactive virtual characters later when we discuss VR interaction, as well as later in this specialization, when we discuss social VR and virtual characters. Animation is not a problem with most 360-degree videos, as in this case, you are just capturing objects and their animation. But a problem is that the only thing you can do once you've captured a video is cut and resequence the video clips. You cannot manipulate objects in the footage like you can with model-based VR. So you would not be able to program the real human actors in the video to rotate their heads to follow the user, at least not in a naturalistic way. [MUSIC]