• Travis Hove

Half-Life Alyx: VR Developer Review

Unless you have been completely unaware of Steam, Road to VR, or just about any gaming Youtube channel, odds are that you have seen a lot about Valve's long anticipated release of Half-Life Alyx. Like many fans of the original series, I could not wait to dive in to a new story, a new world, and a new way to play. Of course, I am talking about virtual reality. This blog post may turn itself into a few videos in the near future once I get my VR Ready PC repaired (ran into some unfortunate graphics card issues, hopefully not too costly). But after playing through the game and really taking the time to analyze it and see some interesting mechanics, I knew that I would want to do a review in the stylings of "VFX Artists React" by Corridor Crew. So let's dive right in to my developer review of Half-Life Alyx!

In this rather lengthy review I am going to be diving into mechanics and game development terminology, while focusing on some of the key areas of the game. Here is the list of sections, if you would like to scroll to a specific portion: - Locomotion and User Interface

- The "Grabbity Gloves", and How they Solve Problems.

- Storytelling in VR

- Sound Design

- Level Design

- Technical Art

- Motion Capture


- Effect on the VR World

- Conclusion

Locomotion and User Interface

If you are like me, the moment you start up any game you immediately go to the settings to see what can be adjusted. Whether it's cranking up graphic settings, adjusting audio levels, or even simply turning on subtitles, a games customization is important to many users. Within the game's first level you are introduced to the basic mechanics and mobility of the game, whose default is set to teleportation. For new users this can take some getting used to when trying to navigate the more intricate parts of the beautiful level designs, but there is good reason for this being the default: motion sickness The game costs $60, and if I get motion sickness on the first level then you bet I will not be happy with the money spent. Teleportation is tried and proven method for VR locomotion with significantly less effects on motion sickness. Games like Robo Recall, Rec Room, and VR chat all use teleportation to keep the player from any less than desireable experiences. Half-Life Alyx would be responsible for bringing a great number of first time users into VR, and that reputation had to come with it. However for experienced VR players such as myself, there were some settings that I changed based on personal preference. The first was locomotion, where I made my left stick control my continuous motion. This is more akin to games like Pavlov and Asgard's Wrath where the player moves how one would expect to in a FPS title. While some find this play style nauseating, I will say that Half-Life Alyx kept to a very good speed and consistent acceleration which alleviates most motion sickness effects.

In addition to changing the movement type I also experimented with a few settings. I personally enjoy playing my games with subtitles in order to get a more clear story. Some developers actually include small tidbits of information in subtitles that players may not pick up on. However, I had never seen a proper execution of this in a VR setting. Half-Life Alyx included a full subtitle and closed captions option (another first for me personally), which moved dynamically with the player's view in a non-distracting way. I kept these subtitles on throughout the first chapter, but turned them off later in the game, wanting to feel more present and immersed in the world.

One thing that immediately grabbed my attention, as "mundane" as this thing may be, was the loading and pause menu system for the entire game. Unfortunately the loading map is only able to be viewed in the headset and not on the screen that most people record and post. Now, I know what you are thinking. This is a brilliant piece of VR history, and the pause menu was one of your favorite parts. As a player, of course there were more exciting and engaging parts. But as a developer, this really caught my attention as a pseudo mechanic within the game.

When developing the alpha build for Cooking with Cannibals, the team and I really struggled with what would make sense as a pause menu for the game. We wanted something unique and possibly interactive, but also something that felt like you were taken out from the chaos of the level for a brief moment. What we ended up doing was creating the "Back Alley" for each level that was in black in white, had smooth jazz playing, and included a cigarette for a smoke break if the player felt so inclined.

In Half-Life Alyx they do a similar take on the pause menu where they drain the world of color (which I am guessing involves post processing on the camera's renderer), but also bring a layer of fog close to the player. This fog allows the player to still orient themselves, but removes the details around them so they do not feel overwhelmed. This also draws the player's eye to the yellow-orange options menus and their holographic feel, making sure that there focus can rest on whatever it is they paused for. In addition to pausing, the game occasionally uses smaller areas as loading zones with the same effect, while also revealing a map of the player's progress. This is an effect that I am hoping to recreate in a future video, so stay tuned!

The "Grabbity Gloves", and How they Solve Problems.

In an article by WHYY, the reviewer seemed rather impressed that in Cooking with Cannibals we were able to pick up objects and put them down. In all honesty, this can sometimes be a challenge in designing for VR. Each hand is not only a controller, but also an object in the game which needs to react appropriately and predictably. Half-Life Alyx does a wonderful job of giving the user consistent control of their environment, while also giving them rules that don't fully break their immersion.

It should be said that I played through the game on an Oculus Rift S, and according to most players the game truly shines on the Valve Index with Knuckles controllers for added hand capabilities. However, even without precise finger motion, I found that the hands reacted precisely as I would have wanted. On top of this, they were even able to turn one of VR's biggest issues into a fun new mechanic: picking up small objects with the R.U.S.S.E.L.L.'s or "Grabbity Gloves."

There are many ways that VR developers handle actually picking up objects. These can range from precise grabs of colliders based on meshes to attaching a joint to an object and parenting it to the players hands. Some developers have even gone as far as to replace the player's hand with whatever it may be that they are holding. Oddly enough, none of these solutions is a wrong solution, and no one solution is the only correct one. However with a majority of grab based mechanics, they rely on predicable behaviors with objects that are either large enough or far away enough from other objects in order to accurately be picked up by the player. Many developers get around this precise selection by including a highlight of the object you will interact with, but Half-Life Alyx takes this a step further. Not only does it highlight what the player intends to grab, but it gives the player the option to pick up objects as small as a single shotgun shell from a distance with a literal flick of the wrist. Once I was given this power, I had to figure out how it worked so intuitively, and I discovered a few clues as to how it works. First, and by far the most noticeable, is the custom hand poses for the objects. Picking up a small shotgun shell makes a pinching motion, while picking up a large box may wrap the fingers around the corner or grip an edge appropriately. This is a fairly common practice for major titles with custom hand models.

The second was the extent of the flick motion and how that effected the object's "flight path" to the player's hand. I did a few tests to see if flicking my wrist vs pulling my hand made a huge difference, and the main factor was actually just the speed of my motion. How I imagine this works is that the motion of the player's hand is being recorded as a vector force, and the check for the player's hand velocity is a multiplier to that vector force. This vector then gets applied to the object you are trying to pull towards you, sending the object flying in that direction. But it doesn't stop there.

The last notable submechanic that I noticed was that that the object's flight path was not perfect, but felt like it while I was playing. If I looked closely enough, the object would change it's moving direction based on where my hand was as I tried to grab it out of the air. Immediately I likened it to the axe-throwing mechanic from the most recent God of War game. The object is keeping track of the position of my hand and adjusting it's path so that I can make a cleaner and more dependable catch. I can assure you that I am not sports oriented, and would never catch that well in real life. However this break in 1:1 controls didn't break my immersion, but heightened it with the satisfaction of using the mechanic correctly time and time again. This gave me a great feeling of diegetic control, without any frustration or significant learning curve. I can only imagine the amount of testing that went into this mechanic, but it surely paid off.

Storytelling in VR

Half-Life Alyx is a linear story complete with action, puzzles, and elements of stealth. But behind all of this is a well crafted story, capped off with a must-see ending (which I will do my best not to spoil for anyone reading). Valve once again has raised the standard of the gaming industry by incorporating story in a way that can only truly be experienced in VR.

The base story is linear in it's presentation, but the story beats are not necessarily predictable. Whether it is the musings of Russell in your headset, or small encounters with Vortigaunts, you have these unique moments which break up any sense of "fetch quest mentality." In addition to this, environmental storytelling and large set pieces really give the player a sense of presence within the world. Again, without spoiling any key plot lines, being able to see the massive structures around you is truly only given its context by the full immersion of a HMD view. I fully believe that every set piece went through iterations and revisions as they make their lines of site for any type of player.

Sound Design

A good portion of the game contains horror elements, and with any horror film or game there is the opportunity for truly unsettling sound design. Half-Life Alyx really shows the potential for 3D sound design in virtual reality. Whether it is listening for headcrabs in the walls, or listening to characters interact with Alyx, you can truly feel the sense of space.

This may be the one negative thing that I have to say about this game. Although most of the sound design really lends itself towards great moments, there are a few choices that did break immersion for me. Namely these were environmental sounds. For example, I would occasionally hear lights flickering or ticking as if a bug was running into them, but I would look up to see fully functioning light bulbs . This led to some confusion for me as I tried to figure out where the sound was coming from since there wasn't a visual cue to accompany it. Other times it was collision sounds not playing the way I would think they would. This often occurred when I threw a metal object at a softer set piece, but would still hear the loud clang of metal on metal impact. Outside of a few overall sound fx issues, I have nothing but praise for the score, dialogue, and other sound mixings within the game.

Level Design

I firmly believed that YouTube gamer Jacksepticeye said it best. "This type of verticality and massive set pieces is exactly what all other VR games should be doing. This is what VR was made for." Half-Life Alyx does a phenomenal job of giving the player's a sense of scale and purpose. Although many of these set pieces serve for driving storytelling along, they provide a certain depth to the actions of the player. Planning for both exploration and confrontation is a huge task, and each level was able to pull it off in a way that seemed fresh and new.

One aspect that really stood out to me was the fact that they had to account for variations in player height. In the player settings you are able to not whether you are sitting or standing during your experience, and will allow controls to aid in any height related difficulties. Standing at 6'2" I will admit that there were portions that I got stuck on since I was not using the teleport mechanic, but the UI popups for allowing me to continue were extremely helpful and a great move for accessibility

Technical Art

This game is beautifully optimized. As someone who has recently been researching development pipelines for asset optimization, I am very impressed with the performance of this game even on a lower spec PC.

One of the greatest shows of attention to detail is their use of maps in such a way that they can get around vertex displacement. A few times during my playthrough I found myself going prone on the floor trying to get an angle where I could see whether certain textures and geometry had displacement maps, or normal and specular combos. I was pleasantly surprised that each map on the environment pieces I observed were done so detailed and optimized that they were able to fool the stereo VR setup.

Half-Life Alyx, like any major video game title nowadays, makes use of modular kits for props and environments. However, one thing that they leverage quite nicely is their use of decals to break up texturing passes and add some unique features to differing sections of the world map. In addition to decals, there is also some notable blending of normals, especially when you observe the more organic alien growths agains hard surfaces like metal and concrete. Very rarely did I find any clipping geometry, and even then I had to look rather closely.

By far what blew me away the most was the lack of noticeable LOD "popping." Usually when running games on lower end PC's, players may notice that details or objects will pop into place as they are being loaded by the game engine. If there was an LOD system in place, it was beautifully hidden. Part of this is due to occlusion culling, as well as some interesting lighting/shader tricks. After having accidentally glitched under the ground, I was able to explore some sections to see how their LODs and rendering played out. I was sometimes met with greybox/white materials as well as some tiling on lightmaps from where I could see. I am hoping to be able to record myself recreating this glitch in the near future.

Blends of organic and hard surface to create unique shapes

Having said that I managed to break boundaries, I was actually surprised I was able to see given Half-Life Alyx's unique orange shader that appears when the player's head goes out of bounds. This is an issue that often goes overlooked in VR development that allows free roam inside structures. There have been some creative solutions such as attaching colliders to the player's head, purposefully occluding outside sections, or even hiding easter eggs and death barriers outside the intended space. However, I liked that this game included something that was immediately recognizable as the player and encouraged you to focus on the core gameplay. Nice touch!

Motion Capture

Vortigaunts, Russel, Eli Vance, the Combine, and many other characters within the game make use of phenomenal motion capture technology. This is not surprising, given the famous G Man demonstration from the original titles. However, this life like movement really lends itself to a suspension of disbelief in the headset. When I first met Russel in his lab and was able to see him react to me throwing things and poking at him, I truly felt like a kid in a virtual candy store. What blew me away more, however, was the first time meeting a Vortigaunt. The first one you meet has some very comedic voice lines and a demeanor that I can only liken to "that one crazy uncle at the family reunion." As someone who did not play the original games when they first came out, it still felt as though I was meeting up with an old friend. Part of the sold realism is found in their improved gaze tracking. Whether this was AI driven or strictly procedural is hard to tell, however each NPC was able to act and react to my actions in a way that seemed rather believable. When combining this level of conversational engagement with unique motion profiles for each character you have a truly immersive experience with a digital being.


As I tell every workshop I have ever taught, particles and shaders are your friend. When we talk about game feel, we go beyond simple game mechanics and into the feeling of satisfaction the player gets from playing. This can be intrinsic, thought provoking, or even artistically driven. And in the case of Half-Life Alyx's weapons cache puzzles, we got a little bit of everything.

Every instance where a hologram or other piece of technology was present, I never questioned it being there. It fit the theme of the game, and didn't seem out of place in it's world. The use of wireframe and scrolling hologram shaders gave a pop of color, but also caused the player to think creatively to solve different puzzles without any true guide beyond visual prompts.

I had mentioned previously that the map and pause menus were a huge selling point to my experience, and a good amount of that experience comes down to the shaders and techniques employed to create them. I found myself examining each dot on the grid to see if it was a sprite or rendered mesh, sometimes shocked by the answers I found. I hope to recreate some of these effects in the near future.


Half-Life Alyx was exactly what the VR industry needed. As I am writing this, the world is still in the midst of quarantine for COVID-19. Part of the reason that I have had time to play this game at all is because of my at home isolation. However, outside of this global pandemic, there is an entire industry of VR creatives still developing paths to the future, and Valve is no exception. Before writing this conclusion, a colleague asked me where VR headsets could be found so he could play Half-Life Alyx. My response was that because of the pandemic it would take some time to ship, but because of this game nearly every headset is sold out anyways. Never has a game brought so many users in and promoted the medium with such intensity and speed. As many reviewers have said before me, this does set a new bar for quality and development for VR titles in the future. I am interested to see if VR continues down this path by following Valve's example. As a developer, it does make me happy to see a VR title of this caliber. However it does make me wonder what will be brought up within the business side of the industry because of this. What were your thoughts? Did you find any interesting easter eggs or development clues? Comment below what you think, and stay tuned for future videos as I explore and recreate content from Half-Life: Alyx. Thanks for reading! Stay at home, stay safe, stay sane, and stay healthy. Wishing everyone the best in these strange and stressful times.

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