Can I please start this video by introducing an old friend of mine, Cristina. She was the very first avatar I have ever created in 2005 when I was doing my masters project. And she was considered to be the most attractive avatar in the lab at the time. Fast forward to 2016, here is a 3D model of myself captured with photogrammetry. I know the hair looks a bit weird, so, I still prefer myself to my avatar and to this can be fixed. Anyway, the point is that in the past 10 years, we have become a lot better in modelling those virtual characters. We have also improved our ability to animate them to behave as if they were real and programmed them to be interactive. This gave us the ability to create realistic, expressive, and responsive virtual characters which have led foundation for having meaningful social interactions in virtual reality. Cristina and my own 3D model, lets call her Sylvia Jr. are both virtual characters. Cristina is more like a comic figure and Sylvia Jr. is more like a real human. In this case, we say that Cristina is cartoon-like and Sylvia Jr. is photorealistic. There's one thing Cristina and Sylvia Jr. have in common, they're both human-like avatars, that is, both their body shapes and facial features are designed to resemble those of a real human. Not all virtual characters are designed this way. Some for instance are designed to look like robots rather than humans. Some of them are humanoid robots often called androids where their body and some facial features resemble those of real humans. We also often see virtual characters designed to look like monsters or animals or even just objects but with human like behaviors. For instance, the characters you often see in animated films. In the Pixar film Cars, there were several anthropomorphic cars and in the movie Toy Story, there were toys who express human emotions. Finally, in the simplest format, virtual characters can be quite abstract. A good example is the game Pac-Man, where you have Pac-Man, the player character and the ghosts. They are the enemies who chase Pac-Man. So, we can rank virtual characters by their human likeness. On top of the rank are Sylvia Jr. and Cristina. They're both human-like virtual characters. But Sylvia Jr. is more realistic than Cristina. At the bottom are probably abstract characters such as Pac-Man and the ghosts. In the middle you can have a range of virtual characters. Some look more like robots, others like monsters, animals or even anthropomorphic objects. As long as they are designed to be able to behave with humanistic characters or personalities, they should go into the big category of virtual characters. So far we've been describing mainly the appearance of virtual characters or video fidelity. How real does the virtual character look. However, when it comes to the realism of a virtual character, there is something else that is considered even more important than how much they look like a real human. And that is, how much they move like a real human or motion fidelity. Motion fidelity is often considered more important because there is more work. You define a video fidelity when you model your virtual character. Sure, that is a lot of work but once you are done with the modeling, your virtual character is there. Motion fidelity on the other hand requires you to think carefully about the animation you apply on the virtual character for each frame. If you have a frame rate of 60 Hz, in order to produce a five-minute animation which is 300 seconds times 60 Hz, you will have 18,000 frames to worry about. Another reason why motion fidelity requires a lot of attention is that, it actually sets the bar for how far you should go in terms of video fidelity. If you have a limited capacity in terms of how realistic you could animate your virtual characters, you should avoid using highly photorealistic virtual characters. Instead, you should go for more cartoon-like or even abstract virtual characters. You should avoid having low motion fidelity animation with high video fidelity virtual characters which are characters, as this will make the avatar look cold and even creepy. This is because the video fidelity sets the expectation. A highly realistic looking virtual character makes you expect highly realistic motion. And if this expectation cannot be met, the whole experience loses credibility in the worst case and even breaks the plausibility illusion which is very important in sustaining immersion in VR.
