Movement is make or break for VR games. A convincing, non-nauseating solution is vital, and Half-Life: Alyx does an admirable job of navigating through that. Valve have explained how they got there, in a new video that brings up sound design, pathing fiddliness, and why they had to ditch a certain system because tall testers kept hitting their virtual heads on low-hanging pipes.
Alyx lets you choose between three movement systems, but Valve spend most of their time talking about the two that involve teleportation. That's where tall people ran into trouble.
Designer Greg Coomer starts talking about height at around 4:30. I was initially outraged, after seeing a taller player get treated to a much clearer view of some ammo stacked on a shelf. I thought Coomer was about to mention it, but nope. Valve made virtual life just as inequitable as shopping for top-shelf cereal.
At least some of the testers got their comeuppance. As Coomer explains: "We would get hard to reproduce bugs from players banging their virtual head on low-hanging pipes because they were unable to teleport through certain areas. It was only later on that we realised all those bugs were coming from our taller colleagues."
With that old build, you were forced to crouch if your teleport path needed you to duck under something. Valve found players were so focused on their destination that they wouldn't notice the problem, so they wound up just letting players teleport to anywhere they could fit. Bring back the height tax, say I.
The sound design stuff is interesting, too, and not just because watching people do Foley effects is always absorbing. As explained by designer Roland Shaw: "A player moving their arm to grab ammo, turning and twisting are all movements supported by sound. When we were developing this technology, we began with just playing some basic Half-Life footstep sounds after each teleportation. Players responded well, so we experimented with using the distance travelled to drive footstep volume and timing."
You also make a louder sound if you jump down from something. The idea was to help ground players in the virtual world, convincing them of their physical presence. It worked, says Shaw: "they began to expect their weight to impact the environment, and hear the results".
You can learn a bit more about Valve's approach to movement in Katharine's whopping Half-Life: Alyx interview, where they mention how players don't find teleportation jarring - as long as they're moving through an interesting world.
Happily, Graham found Alyx's world very interesting indeed. "Valve still make the best first-person shooters around", says he in his Half-Life: Alyx review.