Jason Mitchell, a developer at Valve, discusses the player movement system in Half-Life: Alyx, a virtual reality (VR) game. The game offers three locomotion modes: blink teleport, shift teleport, and continuous locomotion. The team experimented with various prototypes and learned that players focus on their destination and tend to imagine themselves with superhuman speed and agility.
To address these expectations, the team developed a system that ensures the player's end position is valid and the path to get there is viable. They also experimented with different visualization techniques, including showing the player's feet at the target location and presenting virtual footprints along the path.
The team encountered challenges, such as players' height affecting pathing and the need to build trust in the teleport system, especially during combat. To address these issues, they implemented a standard minimum body size, prioritized movement along the floor, and used audio cues to describe the player's locomotion.
The game's locomotion system was designed to be flexible and adaptable, allowing players to choose the method that works best for them. The team's experiments with different prototypes and feedback from playtesters ultimately led to a system that provides a sense of immersion and presence in the virtual world.
Here are the key facts extracted from the text:
1. Jason Mitchell is a developer at Valve.
2. Half-Life: Alyx supports three types of player locomotion: blink teleport, shift teleport, and continuous locomotion.
3. Continuous locomotion is the most similar to traditional WASD mouse and keyboard controls.
4. In teleport modes, the player uses a targeting interface to select the location where they would like to move.
5. Blink teleport involves the screen turning black, the player being moved to the target location, and the screen fading back up from black.
6. Shift teleport is similar to blink teleport, but the screen doesn't go black.
7. The Lab had a combination of specifically authored teleportation locations and room-scale spaces, which was where the developers started their prototypes.
8. The targeting reticle in The Lab was distracting to players in the more realistic environments of Half-Life: Alyx.
9. The developers experimented with showing the player's feet at the target location to present an indicator that was more physically grounded in the world.
10. The presentation of the feet implied the volume that the player's body would occupy.
11. The developers also experimented with presenting the visualization of player footprints, not just at the destination, but along the current path.
12. Players had a great reaction to the virtual footsteps because it allowed them to visualize themselves moving over and around obstacles.
13. The virtual footsteps are a visual representation of the pathing system.
14. The developers initially tried repurposing their existing nav mesh system, but it proved to be too rigid.
15. The nav mesh system precomputes all possible movement paths.
16. The developers used the ASTAR system to build routes, but it was too computationally intensive.
17. Players have a strong tendency to focus on the destination and see the rest of their environment as a potential obstacle.
18. Players imagine themselves to have super-human speed and agility.
19. The developers' initial tests and playtesters' desires led to the system they have today, which ensures that the end player position is a valid place for the player's body and that the path to get there is viable.
20. The height at which players view the virtual environment is very important and affects the way paths are computed.
21. The developers used a standard minimum body size to validate the middle portions of the teleport path.
22. The teleport system needed to perform a player's desired movement even if they were performing quick and coarse gestures.
23. Two key elements were essential to gaining players' trust: prioritizing movement along the floor and moving players partially along their desired paths.
24. Prioritizing the floor is the teleportation version of the concept of moving in a plane.
25. In combat, the player's focus is on the enemy and not on the environment.
26. Playtesting showed that players teleport targeting becomes frantic and imprecise in combat situations.
27. The system needs to match player expectations, even in combat situations.
28. The teleport system achieves reliable results by moving players partially along their desired path in certain cases.
29. Partial movement occurs at drop-offs, where heights are very impactful in VR.
30. The result of partial movement is a natural pause that allows the player to view the terrain below and make a better-informed decision about how to proceed.
31. The developers used audio to describe the player's locomotion after they teleport.
32. Sound is used to describe and support all kinds of body movement, such as moving arms, crouching, and twisting.
33. The developers experimented with playing basic Half-Life footstep sounds after each teleportation.
34. Players responded well to the footstep sounds and provided feedback that they expected to hear a louder, heavier sound when teleporting from a high to a low area.
35. The game is in the hands of customers, and players who prefer different styles of VR locomotion have been able to select the option that's most comfortable for them.
36. The fact that multiple locomotion systems were implemented together meant that each of them was stronger because they could borrow ideas from each other.