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Commentary node

The commentary node model that was used in the Half-Life 2 series.

Commentary node grey

Commentary node model skin used after the commentary has been listened to.

The in-game Developer commentary, turned off by default, is intended to give players an insight into the development process of the game, as well as offering interesting information which might not have been obvious initially.

Valve introduced the feature in Lost Coast and later introduced it to Episode One, Episode Two, Portal, Portal 2, Left 4 Dead, Left 4 Dead 2, Team Fortress 2, and Half-Life: Alyx.


  • The icons can be activated by enabling developer commentary from the options dialog box. Pressing the USE key whilst the crosshair is hovering over the icon in-game causes them to begin playing, and the same key again stops the sound. Distance from the icon is not a factor, as an icon can be activated from any proximity as long as it is visible.
  • The icons play recordings of Valve team members or voice actors, who talk about behind-the-scenes information, including how or why they made the map, an enemy, a character, or a storyline idea, what happened in the earlier iterations of the map or area, and in the voice actors' case, how they coped with the voice acting.
  • Sometimes, the nodes will take control of the player's camera in order to show different areas or techniques. An example of this can be seen in Lost Coast; the screen is separated down the center to show the difference in rendering with HDR enabled and disabled.
  • Activating a commentary node will also activate a number of side effects depending on the game: temporarily disabling the game's AI, as in Lost Coast, or rendering the player invulnerable to enemy attacks, as in the Half Life 2 Episodes. To counter this, achievements cannot be unlocked whilst in commentary mode (except in the case of Portal 2's Single Player), as it makes the game easier. Activating a commentary node will not stop music or sounds.
  • On all Valve games, the co-founder, Gabe Newell, will make the introductory commentary, which usually consists of an explanation of how to control the nodes. At the end of some games, he will make the final commentary.


Half-Life 2: Lost Coast[]

Half-Life 2: Episode One[]


Half-Life 2: Episode Two[]

Comment 001.wav by Gabe Newell

Location: ???

"Welcome to Half-Life 2, Episode 2. We are at the mid-point in our trilogy of episodes which will conclude in Episode 3. To listen to a commentary node, put your crosshair over the floating commentary symbol and press your use key. To stop a commentary node, put your crosshair over the rotating node and press the use key again. Some commentary nodes may take control of the game in order to show something to you. In these cases, simply press your use key again to stop the commentary. Please let me know what you think after you have had a chance to play this, our latest installment in the ongoing adventures of Gordon Freeman. I can be reached at gaben@valvesoftware.com. I get about 10,000 emails each time we release a game, and while I can't respond to all of them, I do read all of them. Thanks, and have fun!"

Comment 002.wav by Erik Johnson

Location: ???

"This transmission scene was added fairly late in development, after hearing from playtesters that they weren't sure where they were going, or why. Setting up the White Forest base as your goal right away was important in an episode with so many open, freeform areas where players might forget what they're supposed to be doing."

Comment 003.wav by Marc Laidlaw

Location: ???

"In this first part of the episode, we are restoring the player's connection to Alyx by recalling the sort of collaborative activities you shared with her in Episode 1, from combat to collaborative puzzle solving. Notice that as she works to restore power to the transmitter, she is careful not to steal the player's fun by doing it all herself. She doesn't actually solve the puzzle, although she sometimes thinks she has. This adds to her charm and helps her feel more human. Of course the reason we're doing this is so that you will care when bad things happen to her."

Comment 004.wav by Jeremy Bennett

Location: ???

"The view of the ruined yet still dangerous City 17 is a good example of a classic Half-Life vista. Vistas are sweeping scenes where many elements of design come together. This one reminds the player of what he accomplished in Episode 1, while setting up the threat that will hang over the rest of Episode 2. It establishes the mood with a stunning skybox and shader effects; shows off believable character responses, and also literally sets the episode into motion. When the player looks at the scene, a device called a 'look trigger' sets off the portal storm, which causes the bridge to collapse, using Valve's new 'Cinematic Physics' which we will be showcasing throughout the episode."

Comment 005.wav by Jason Mitchell

Location: ???

"For the ominous mass of clouds which swirl above the destroyed citadel, we devised a shader effect to give the impression of depth and complex turbulence. The actual geometry rendered for this effect is a single flat polygon but, through a series of pixel shader effects which composite several texture layers, we are able to achieve the impression of realistic churning clouds. In the offline previsualization work that we did to initially define this effect, we developed a very realistic simulation with more than 30 layers of clouds. With real-time shader techniques, we were able to achieve an equivalent look while maintaining an interactive frame rate."

Portal 2[]

List of appearances[]