Half-Life: Alyx - Half-Life: Alyx Team

Join the Half-Life: Alyx team in a behind-the-scenes deep dive that examines locomotion and player presence in the game. Valve developers Jason Mitchell, Luke Nalker, Greg Coomer, and Roland Shaw share some of our early prototypes, and walk through user interface, audio, and player movement discoveries that led to the game's final designs.

Jason Mitchell: My name is Jason Mitchell, and I'm a developer at Valve. Today, some colleagues and I would like to share with you the details of the player movement in Half-Life: Alyx. Traversing space is a fundamental challenge in VR generally, and we have spent considerable effort on our locomotion system. We'd like to take this opportunity to talk about some of our early prototypes and some of the more interesting things we learned along the way.

In Half-Life: Alyx, we decided to support three different types of player locomotion: Blink teleport, shift teleport, and continuous locomotion.

Continuous locomotion is the most similar to traditional WASD mouse and keyboard controls. This allows players to move smoothly through the environment without teleporting. In both teleport modes, the player uses a targeting interface to select the location where they would like to move.

In blink teleport, the screen turns black, the player is moved to the target location, and the screen fades back up from black with the player at the new position. This all takes place in a fraction of a second.

Shift teleport is similar, except the screen doesn't go black, and the player is rapidly moved to the selected location. Today, we're going to dive into the details of the blink and shift teleport modes.

Luke Nalker: Since we already shipped blink teleport in The Lab, it was a natural place for us to start our development. The Lab had a combination of specifically authored teleportation locations and room-scale spaces, which was where we started our prototypes. While the targeting reticle worked well in The Lab, it turned out to be distracting to players in the more realistic environments of our game.

In order to present an indicator that was more physically grounded in the world, we began experimenting with showing the player's feet at the target location. This had the added benefit of enabling the player to select the desired orientation at the teleport destination. The presentation of the feet implied the volume that the player's body would occupy, which was especially important when moving to cover during combat.

We also experimented with presenting the visualization of player footprints, not just at the destination, but along the current path. Players had a great reaction to this because it allowed them to visualize themselves moving over and around obstacles, as well as understand why some desired movements may not be valid.

Greg Coomer: Those virtual footsteps you see are a visual representation of our pathing system. Initially, we tried repurposing our existing nav mesh system, which is the same one our AI uses to navigate. In practice, however, this proved to be too rigid. The nav mesh system precomputes all possible movement paths. And while that's efficient, it didn't support the locomotion and interaction desires of our players or our designers, who were building very dynamic environments.

This led us to our next series of tests, using the well-known A* system to build routes. Our A*-based teleport pathing approach was successful in that it freed players from having to micromanage their teleport targeting. Ultimately, it was too computationally intensive, so we had to explore more efficient solutions.

During these early experiments, two things became pretty clear to us: First, players have a strong tendency to focus on the destination, and the rest of their environment is seen as a potential obstacle to them getting where they want to go. Second, players imagine themselves to have super-human speed and agility. Playtesters would happily tell us that, yes, in fact, they could reach that spot by squeezing through a gap, catapulting over an object, or sliding under an obstacle.

Ultimately, our initial tests and playtesters' desires led us to the system we have today, the main goals of which are to ensure that the end player position is a valid place for the player's body and that the path to get there is viable. To get to this point, we had to solve a whole variety of problems. Some of the more interesting ones are things like how player height has an impact on pathing. Also, building player trust in the system and keeping players grounded in the world just using audio.

When we talk about a viable path, we mean one where the representation of the player's body in the virtual environment stays intact. Players obviously can't squeeze in between jail bars or fit into a tiny mouse hole or do things like jump hundreds of feet up onto ledges. But they can crawl, turn, or contort, or engage in their environment in a way that stays true to their physical shape.

Traditional video games put the world in front of you, and, as a player, you have expectations about your ability to navigate and act on the world. But movement in VR generates so many more player expectations because the world completely envelops the player. Players actually lean around corners. They even get down on the floor to try to peek under doors.

It turns out that the height at which players view the virtual environment is very important. We as humans are strongly attuned to the perspective that our height gives us on the real world, and it was essential that we preserve this in the virtual environment in Half-Life: Alyx. The result of this is that the extent of each player's virtual body is subtly different due to the variation of their real-world height. And this affects the way paths are computed. In fact, early on, we would get hard-to-reproduce bugs from players banging their virtual head on low-hanging pipes 'cause they were unable to teleport through certain areas. And it was only later that we realized all those bugs were coming from our taller colleagues. At the time, our system required players to crouch down to the minimum height along their desired teleport path. But players frequently failed to notice that or understand it. They were focused on their goal, not realizing that, halfway through their path, there was an obstacle they needed to crouch under during their movement. So to solve this, we decided on a standard minimum body size, which was used to validate the middle portions of the teleport path and only required that the start and end positions could support the actual presence of the full-size player.

Jason Mitchell: At the core of all Half-Life games is a particular mix of story, puzzle, and combat experiences. In order for the combat experiences in particular to succeed in VR, it was essential that we built players' trust in the teleport system. Ultimately, we wanted the teleport interface to fade into the background, enabling players to concentrate fully on the combat scenarios. This meant that the teleport system had to perform a player's desired movement even if they were performing quick and coarse gestures. During development, we discovered two key elements that were essential to gaining players' trust: Prioritizing movement along the floor and, under certain conditions, moving players only partially along their desired paths.

If you think about a traditional first-person control scheme, you have forward, back, left, right, strafing. All of these movements happen in a plane. When the player wants to leave the plane, they have to do something explicit, like jump or climb a ladder. Prioritizing the floor is the teleportation version of that concept. In combat, the player's focus is, as you would expect, on the enemy and not on the environment. Playtesting has shown us that players teleport targeting becomes frantic and imprecise in these situations. And even under these conditions, our system needs to match player expectations. Typically, players want to stay in contact with the floor and move out of danger, not jump up and down on all the objects in their environment in the middle of a battle. Floor prioritization achieves this.

Another way that our teleportation system achieves reliable results, even when used quickly and imprecisely, is by moving players partially along their desired path in certain cases. In the heat of battle, players focus on quickly repositioning themselves for tactical advantage. Instead of requiring the player to precisely specify a valid teleport destination, partial movement moves the player as close as possible to the desired location along the valid movement path. As a result, players don't have to shift their mental focus away from their enemy in order to move during battle.

Another variation of partial movement occurs at drop-offs. Heights are very impactful in VR, and dropping into a new environment, especially one that was not visible prior to committing to the teleport, can be very disorienting. To address this, we also perform partial movement when a player's end position is not visible from their starting position. The result is a movement up to the edge of the cliff or the drop-down, creating a natural pause that allows the player to view the terrain below and make a better informed decision about how to proceed.

While we want the locomotion system to become effectively invisible, it's also important that the player's subconscious remains aware of their presence in the virtual world. Sounds are used as a constant, subtle reminder of the player's presence in the game.

Roland Shaw: Teleporting in The Lab and SteamVR is supported with a relatively abstract sound. But that's not consistent with the more grounded realism of Half-Life or with the visual and haptic cues we are providing players in Half-Life: Alyx. So rather than a simple, abstract teleport confirmation sound, we use audio to describe the player's locomotion after they teleport.

This isn't something that's limited to teleporting; we use sound to describe and support all kinds of body movement. For example, a player moving their arm to grab ammo, crouching, turning, and twisting are all movements supported with 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 traveled to drive footstep volume and timing. They also started providing feedback that they expected to hear a louder, heavier sound when they teleported from a high to a low area, effectively jumping down in virtual space. This kind of feedback convinced us that players were feeling as if they had a physical presence in VR. They began to expect their weight to impact the environment and hear the results. We implemented that feature and iterated based on further feedback.

Jason Mitchell: Now that the game is in the hands of customers, it's exciting to see that players who prefer different styles of VR locomotion have been able to select the option that's most comfortable for them. Interestingly, the fact that we implemented multiple locomotion systems together meant that each of them were stronger because they could borrow ideas from each other. For example, the fluidity of continuous locomotion influenced the design of the teleport system. Likewise, the audio cues that we developed to summarize the player movement during teleports were integrated back into the continuous locomotion mode to provide the same kind of player feedback. So in the end, no matter which locomotion method players select, they'll be able to move confidently through the complex environments of Half-Life: Alyx.
Half-Life: Alyx - Half-Life: Alyx Team
  • Added full-featured support for left / right hand for movement controls, independently of left / right hand for weapon controls.
    To use this: Select Left / Right hand in the in-game UI, and then select the desired Weapon / Off-Hand bindings in the SteamVR controller bindings UI.
  • Added an option to draw subtitles and captions to the spectator window only.
  • Clarified Height Adjust accessibility options, and set better defaults across various controllers.

Performance notes:

  • Fixed a UI issue where graphics settings would appear to drop from Medium to Low.
  • Fixed not being able to use Quick Back, Shift-Dash-Jump, and teleport feet rotation when Controller Turning was turned off.
  • Fixed a case where loading a left-handed savegame from the Main Menu could cause the player to lose ammo.
  • Fixed savegames where the SMG was missing parts of its model.
  • Fixed a number of crashes.

Content Build ID: 4831658
Half-Life: Alyx - Robin
  • Improved turning options in Preferences:
    - Added "Continuous Turn", and associated turning speed options.
    - Renamed "Quick turn" to "Snap Turn" to make its functionality clearer.
    - Added option to disable controller turning.
  • Improved hand-over-mouth pose usability for Windows MR controllers.
  • Improved the resolution of impact decals on enemies.
  • Improved automatic detection of default Quality settings for some machine configurations.
  • Fixed an issue where some sounds didn't play as intended.
  • Fixed an issue where the main menu could become less responsive if you had many save games.
  • Fixed several crashes.

Content Build ID: 4815971
Half-Life: Alyx - augusta
It's here. Half-Life: Alyx, Valve's long-awaited return to the Half-Life series, is NOW AVAILABLE to play. Compatible with all PC-based VR headsets, the game has been designed from the ground up for virtual reality. Half-Life: Alyx can be purchased from the Steam store and is available for download and play immediately.
Half-Life: Alyx - Gregori

On Monday March 9th, the Valve Index VR system will be made available again for purchase after having been out of stock for some time. Recent demand for the Index system has been high, so we do expect that available stock on hand will sell out quickly. We will continue to take orders after those units have been sold, so purchases beyond this initial quantity will be fulfilled in the order in which they are received, as supplies increase over the coming months. The exact time that the Valve Index will be made available on Monday is 10:00 AM Pacific (5:00 PM UTC).

If you already own a Valve Index, or have ordered one, the bonus Half-Life: Alyx preview locations have just been released and are now accessible to you via Steam VR Home. Starting now, you can download and visit two locations from the game, before the game comes out on March 23rd. One is an outdoor space taken from City 17 in the shadow of the under-construction Citadel. The other is Russell's laboratory, where he helps Alyx make plans to take on the Combine. The rendering technology available in SteamVR's native environments is different than that in Half-Life: Alyx, and the interactivity is significantly lower than what the game itself provides. So while these scenes do not have quite as much fidelity as they will in the actual game, we think they are a faithful enough translation to provide a fun VR preview of the game's setting.

If you don't own a Valve Index but would like to check these environments out in VR before March 23rd, you can ask an Index owner to host a SteamVR Home session for you.
Half-Life: Alyx - chrisr
Half-Life: Alyx releases to Steam on March 23, 2020. Today we're releasing three gameplay videos, showing a variety of environments and play styles. Each one is a live capture of the game running in real-time, featuring one of the locomotion mode options available to players: Teleport, Shift, and Continuous.

Half-Life Alyx is playable with all SteamVR-compatible headsets. Bonus content for those who own Valve Index hardware prior to Half-Life: Alyx's release will start rolling out this Wednesday, starting with a set of SteamVR Home environments showcasing locations from the game.

For more coverage of Half-Life: Alyx, including a longer unbroken section of gameplay, visit https://www.ign.com/videos/half-life-alyx-9-minutes-of-gameplay-ign-first.

Half-Life: Alyx - contact@rockpapershotgun.com (Matt Cox)

In Half-Life: Alyx you will be able to trap headcrabs, the prime nemesis of footlobsters, inside buckets. “It’ll move the bucket as it crawls around”, confirmed the Half-Life: Alyx team in yesterday’s Reddit Q&A, adding that “playtesters all keep reporting it as a bug”. I hadn’t given all that much thought to Half-Life: Alyx but this is honestly a game changer. It’s a little crystallisation of what a Half-Life VR game actually means; something I can clearly see myself doing and enjoying.

Lauren’s already reported that Valve are confident the game won’t be delayed, but I’ve scoured the AMA for other tasty titbits, such as the fact that the 80 people working on Alyx are the “largest single team” Valve’s ever had.


Half-Life: Alyx - contact@rockpapershotgun.com (Lauren Morton)

Delay season has hit the big games of this year pretty hard. Several large releases have been pushed back from their early 2020 estimates to several months down the line. Some haven’t given new estimated dates at all. Today, Valve says they’re confident that they won’t miss Half-Life: Alyx‘s planned release.


Half-Life: Alyx

Do you have questions about Half-Life: Alyx—like, maybe, when are we going to get a proper release date? If yes, you'll want to tune into Reddit tomorrow at 9 am PT/12 pm ET for an AMA with the development team.

The presence of the word "some" can't be overlooked, but even so the reaction on the Half-Life subreddit where the AMA will take place is bouncing rapidly between excitement and surprise at Valve's apparent newfound openness. As redditor DaftVortigaunt put it, "If you had told me a year ago Valve would suddenly be openly communicating with their fanbase, I would not have believed it. Looking forward to it!"

Or, as santumerino said more succinctly, "What the fuck, Valve communicating?"

It's not known who from Valve will be attending the AMA, but the moderators are clearly anticipating trouble: They warned that the AMA will be focused on Half-Life: Alyx, and asked all participants to "please limit jokes about Half-Life 3."

We'll be keeping an eye on the AMA, as we do, and we'll let you know what interesting things are said. And in case you missed it, Valve made the entire Half-Life Collection—Half-Life, Half-Life 2, HL2: Episodes 1 and 2—free to play today, until Half-Life: Alyx launches.

Half-Life: Alyx - Gregori

Half-Life: Alyx is coming in March, and we are celebrating early by making all games in the Half-Life Collection FREE to play for Steam users, from now until the day it launches!

Half-Life: Alyx is set before the events of Half-Life 2 and the episodes, but the games share characters and story elements. The Half-Life: Alyx team believes that the best way to enjoy the new game is to play through the old ones, especially Half-Life 2 and the episodes, so we want to make that as easy as possible.

From now until Half-Life: Alyx launches, visit the game page of each Half-Life game to install it and play as much as you want, right up until the day Half-Life: Alyx is released!

If you already have Steam installed, you can click the following links to start playing now!
Half-Life 2
Half-Life 2: Episode One
Half-Life 2: Episode Two

Also included in this bundle and available to play for free are:
Half-Life: Opposing Force
Half-Life: Blue Shift
Team Fortress Classic

If you don't have Steam, you can download it here.

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