Putting a photo or video into a virtual world is an extension of texture mapping. Figure 7.22 shows a commercial use in which Netflix offers online movie streaming through the Samsung Gear VR headset. The virtual screen is a single rectangle, which may be viewed as a simple mesh consisting of two triangles. A photo can be mapped across any triangular mesh in the virtual world. In the case of a movie, each frame is treated as a photo that is texture-mapped to the mesh. The movie frame rate is usually much lower than that of the VR headset (recall Figure 6.17). As an example, suppose the movie was recorded at 24 FPS and the headset runs at 96 FPS. In this case, each movie frame is rendered for four frames on the headset display. Most often, the frame rates are not perfectly divisible, which causes the number of repeated frames to alternate in a pattern. An old example of this is called 3:2 pull down, in which 24 FPS movies were converted to NTSC TV format at 30 FPS. Interestingly, a 3D movie (stereoscopic) experience can even be simulated. For the left eye on the headset display, the left-eye movie frame is rendered to the virtual screen. Likewise, the right-eye movie frame is rendered to the right-eyed portion of the headset display. The result is that the user perceives it as a 3D movie, without wearing the special glasses! Of course, she would be wearing a VR headset.
Steven M LaValle 2020-01-06