Portal 2 developer commentary: Difference between revisions

=== Big Door ===

| The size of the gigantic transition seal lock was a happy accident. We knew the connection between old Aperture and new Aperture had to be a big set piece. The first model built was about five times bigger than everyone expected, but people started to like it.  We joked that it should be a bullet point on the Portal 2 box: "Features the biggest door in games ever!"  We decided it would be fun to play with the player's expectations and put a puny looking door behind it, along with a few small props.

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=== Janitor Bob ===

| We had to come up with old-looking versions for all the important gameplay props, such as button panels, doors, cubes - basically everything the player could interact with. We came up with this fictional character - Janitor Bob. He'd be the guy who had to maintain all of old Aperture. A guy who doesn't understand anything about science but can fix everything with duct tape and a screwdriver. He would use everything he could get his hands on. The result might not look pretty but it would work. So whenever we got stuck designing props for chapter 3 we'd ask ourselves: "Well, how would Bob build it?"

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=== The Eye Has It ===

| How do you make a giant mechanical eyeball express life and emotions, let alone give the impression that he's talking when he has no mouth? The animator's understanding of human behavior came in handy for bringing Wheatley the personality sphere to life. Talking is so much more than just moving a character's mouth. You have to use body language, head attitudes and rhythm of movement and eye focus to indicate a character's feelings and motivations. Slow, smooth head moves, a steady gaze and a relaxed eye aperture indicate that Wheatley is calm. Short, sharp head turns, rapid blinks and glancing around indicate nervousness or deceit. Add a tightly constricted eye aperture and a little shiver to show fear. Tilting the body away while keeping the eye focused on the player signals an attempt at cleverness that ultimately only fools Wheatley himself. Suspicion is communicated by squinting his eyelids and handles, which function as very expressive eyebrows and cheeks. It's also fun to remind the player that Wheatley is a machine. When hacking, his eye and body segments become perfectly centered and spin mechanically, inspired by the spinning tape reels on old Univac computers. And when he wants to look far in front, he flips his eye all the way over to the other side of his head. This animation approach combined with the writing and vocals makes Wheatley quite a unique and entertaining character--part human, part machine, all eye, and no brain.

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=== Elevator Fatigue ===

| We found that playtesters were getting fatigued at solving so many complex test chambers in a row. So, instead of a routine elevator ride to the next puzzle, we added a long funnel ride with some destruction to give players a short break while reminding them of the facility's state of disrepair.

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=== Catapult Intro ===

| This was the first test map we created when we started to experiment with the Aerial Faith Plate puzzle element. The map underwent many visual refinements, but it's one of the few puzzles that remained almost completely unchanged from its first form.

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=== Reference Materials ===

| While making Portal 2, we explored our way through vast quantities of reference material. Inspirations included photos of NASA’s Apollo and Shuttle programs, CERN’s particle accelerators both modern and obsolete, industrial robots, derelict Soviet space shuttles, overgrown temples, Brussels metro stations, seedy American motels, junkyards filled with rocketry equipment, Chinese apartment blocks under construction, Polish shipyards, neutrino detectors deep underground in nickel mines, corporate headquarters from a variety of eras, commercial nuclear reactors, experimental fusion reactors, rain-sodden book depositories in Detroit, peculiar cameras, forgotten space probes, you name it.

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=== Kill Your Television ===

| In each of Wheatley's test chambers there is always a monitor with Wheatley on it. While placing the monitor in this level, one of our designers thought it would be funny if the monitor was the target of the faith plate and would get broken if the player or the box flew into it. We thought the gag worked well and decided to make every monitor breakable.

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=== Nonlinear Progression ===

| The original layout of this chamber started out much more linear; essentially a sequence of rooms that the player had to progress through somewhat blindly – not knowing what the next goal might be until they got there.  Early versions contained an extra puzzle beyond the reflector cube, but due to the linear path, it took players so long to get to it, that they were confused about which elements were still relevant. This drove us to make the level nonlinear.  To make it easier for players to visualize the puzzle, we condensed the overall test space and moved the exit near the start. This helped the players see where they had to go and which objects would help them get there.

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=== Blobulator ===

| The first implementation of the blob was integrated in the Source engine back in 2007. Over the years, the code has been significantly optimized, but was still way too slow to run on game consoles. The blob was a key feature of Portal 2, even though we did not know if we could make it work for consoles. In summer 2010, we were still considering using a completely different tech for consoles--one that would certainly not look as nice. On the 360, even with a very low quality blob, we were barely within our performance budget. But we really wanted to have the same high quality blob among all platforms. Meanwhile, the code was poorly suited for PS3 SPU. We ended up re-writing all the blob code so it would take better advantage of multiple cores and SPUs, giving us quality blobs on all platforms while staying within performance and memory constraints.

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=== Flight Paths ===

| The catapult trajectory lines seen here allow us to visualize where the catapult will deliver a player or a physics object.  We can differentiate the speed and trajectory for players and other objects.  The yellow lines are for physics objects, and green is the player's trajectory.  Sometimes we need to have a different value to accommodate the shape of the objects being catapulted.  What works for the player may not work for an object, and vice versa.  For instance, it was common for a box to make it to a ledge while the player would smack into the side and then fall into the slime. The visualization tools helped us debug these types of problems

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| GLaDOS originally was a lot more cutting in these opening rooms, given that she’s talking to someone she perceives as her murderer. Playtests revealed, though, that it was a bit grueling getting brow-beaten by GLaDOS this early in the game, so her arc was rewritten to give her more of a slow burn towards the player.

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=== Many To One ===

| Wheatley was originally envisioned as a group of spheres that you’d discover as you explored the facility behind the scenes. We ditched this idea for two reasons. For one thing, ‘behind the scenes’ levels were required to highlight the introductions of each of these new spheres and these levels have their own unique logic.  The number of spheres we wanted would have made for far too many of these types of levels, resulting in a very un-Portal-like game. Also, we were spending so much time introducing these new characters that we had no time to get to know any of them before they were swept offstage for the next one. Eventually we realized it’d be a lot more satisfying to really get to know one sphere instead of briefly meeting six.  Some of these characters were eventually recycled as corrupt cores for the finale.

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=== Horrible Accents ===

| The breakout sequence here was originally a lot longer, involving Wheatley talking to you in a horrible American accent, assuming GLaDOS can't hear him. Simultaneously, we'd have GLaDOS commenting on the entire ridiculous exchange, because of course she can hear him. When we playtested the concept, every player made a beeline for the opening. So we either had to ditch all the dialogue or figure out a reason for the player to stand around for five minutes even though they could escape at any time. We ditched the dialogue.

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=== Caroline ===

| The character of 'Caroline' came about because we wanted somebody for Cave to play off of.  Though we had originally envisioned a put-upon Scientist character called Greg, it would have been wasteful to hire an actor for just one or two lines.  Instead, we hit upon the idea of economizing by using GLaDOS-actor Ellen McLain.  Out of nowhere, we suddenly had an opportunity for a GLaDOS origin story.

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=== Potatos ===

| The character of PotatOS was actually the hardest one to crack for us, and was the last character to get recorded. We’d always wanted to switch things up for the sequel, so that GLaDOS would become your unwilling buddy cop partner against a new threat, but this ended up being far more entertaining as a concept than in execution. It’s one thing to have an omnipotent villain chastising you while you’re testing. It’s quite another to have a little potato on your gun doing the same. Playtesters wanted to tear her off the gun, and we didn’t blame them. So we were faced with the unsettling prospect of making dry, robotic supervillain GLaDOS more human and relatable. This ended up being one of the hardest writing jobs in the game.

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=== Birdbrain ===

| One of the larger plot holes that PotatOS introduced was: She’s your buddy now. She’s got the same goals as you. So why isn’t she helping you solve the tests? The real answer is, obviously, that if she did help you solve the tests there’d be no game. One solution we we came up with was for the bird from Act 3 to keep swooping in and pecking bits of her off your gun. As the bird kept eating the part of her that knew how to solve the tests, PotatOS would actually get dumber over time. For technical reasons, this ended up being impossible to execute, so we ended up finding another solution. Some of us though will always have a place in our heart for the bird solution.

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=== Evil Wheatley ===

| Finding the right balance for Evil Wheatley was difficult, because we still wanted him to be the bumbling idiot from the first half of the game, but at the same time, there had to be some sense that he was dangerous now, otherwise there wasn't much tension for the big finale. Fortunately, Stephen Merchant did a great job of intercutting funny bumbling Wheatley with occasional outbursts of power-mad, villainous Wheatley.

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=== Decorating Aperture ===

| This chapter gave us a great opportunity for visually telling the backstory of Aperture Science. We accomplished this with signs, props and materials. In this area, we get a glimpse of what Aperture Science must have been like in its heyday. We used rich, warm colors and materials like carpeting and marble to indicate that Aperture had a lot of money at one time. Cave Johnson and his staff were just starting out in their enterprise and everyone was eager to do science. This stands in contrast to the stark, cavernous environment outside and the materials you see in the Aperture Labs from later decades. As the player makes their way through more recent areas of the lab, the materials become cheaper, with an abundance of plastic and linoleum showing that Aperture had fallen on harder times and could no longer build high-quality offices for its workers.

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=== New Sounds And Old ===

| The newer and older versions of Aperture show their distinct personalities in sound as well as visuals. The doors, floors and buttons, as well as soundscapes, reflect the aging, outdated 70’s feel. The sounds contain hints of the decaying metal and wood. The newer but unstable Wheatley chamber soundscapes become more foreboding and perilous the further you venture into them. The atmosphere of uncontrolled destruction continues to intensify till the end.

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=== Gel Sounds ===

| With the gel sounds for Portal 2 we wanted to create something whimsical that would add to the player’s enjoyment of the mechanics, without crossing over the line into ludicrousness.  For example, our initial pass at the blue gel 'bounce' sound included a rubber playground ball, a pitch-bent harp string and a processed mouth harp.  The resulting sound captured the idea of fun, but was off the charts on the goofy scale.  After several iterations we settled on the current, less over-the-top sound which features a piece of metal bar bouncing like a diving board and a heavy dose of synthesis.  It’s not as wacky, but hopefully it’s still fun.

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=== Turret Building Machine ===

| We felt that most players of Portal, ourselves included, wanted more opportunities to look behind the scenes of Aperture--and not only into deserted crawlspaces, but into the vital heart of the factory.  The turret factory was a way for us to satisfy this desire, while also answering the nagging question of where all the stuff in the facility came from.  Because we constantly allude to the turret creation process throughout the game, it is satisfying from a story standpoint, to finally stand before the machine you've been hearing about.  By showing how turrets are made, it's easy enough to extrapolate a similar creation path for all the other items that Aperture generates only to be consumed by the endless process of product testing.  We designed an entire life cycle for the poor doomed turrets, from creation, product testing, error detection, packaging, and their ultimate unpackaging prior to being recycled.  In fact, the turrets never make it to shipping.  As soon as a turret is completely finished and packed in a box, it is immediately sent to the un-boxer, where it goes on to recycling and begins its life anew.  Thus we show Aperture continually building and repurposing its items in the most inefficient way imaginable.  We never got around to building the actual unboxer, but what we pictured was that it was located immediately below the boxing machine.  And while the turrets would be reduced to their components, the boxes would be discarded and end up in a steadily growing mountain of unrecycled packing materials.

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=== Frankenturrets ===

| The Frankenturrets were an attempt to show one of the ways Wheatley has been spending his time since he threw the player down into the Underground. Using his limited brain, it didn't seem like he could have come up with a lot, so the idea of using objects he'd have access to seemed appropriate. The turret and the cube are the two most iconic portal objects and the frankenturret is little more than a crude combination of those two objects.  The hermit crab animation when you pick the cubes up began as a necessity because we really needed to make them act like cubes when you held them. It ended up being so cute that it became a simple job of making the turret widen its eye and shake its head a little, to convey to the player that these things were disrupted, and had no idea who or what they were anymore, and also to make the player feel sympathetic towards their plight. We used a combination of  in game physics pushes and canned Maya animation to allow the player freedom to move them wherever they wanted, line up races between them, or even set them up so they would walk, inevitably to their doom, into a fizzler.

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=== Wheatley Model ===

| The Wheatley model was designed as a mechanical version of the original Portal 1 personality sphere. Originally they filled a very similar role to that in Portal 1,  so we needed one base model which could hold a lot of different expressions. Experimenting with different rigging ideas we came up with the onion skin design where a number of spherical plates could slide around inside each other all supported on a small motion platform mounted on a gyroscope. This meant that no matter what expression Wheatley was pulling, he always retained his spherical shape. The modelers and the animators collaborated closely on these early tests to make sure the design supported the range of expression needed to satisfy any personality sphere that got designed. Lots of ideas were thrown out, such as a small internal robot arm that Wheatley could pull out of one of his ports and pull himself around with. We were careful to make the mechanics look plausible, but we had to cheat the eyelids, since they ended up being a physical impossibility.  There was no way all that geometry could fit into the space around his eye without clipping out the other side, but they were such an essential feature of the model that we resorted to crushing them up inside the eye where the player can't see them.

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=== Vacuum Transport ===

| Vacuum pipes cropped up occasionally in the original Portal, but this time we wanted to show that this was the main way that Aperture transported all of its supplies about the facility. It felt very true to Aperture, in that it seemed like an inefficient and ridiculously expensive solution to their transport problems. We also wanted it to feel more violent and physical than before, with objects constantly ricocheting against the sides of the pipes.  It was as if Aperture had no real control over the system, and no real care for the things they were transporting. After all, they have thousands of the things.

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=== Arms Asleep ===

| When the player first encounters the robot arms, we wanted to convey that they were still coming back online.  The idea was that GLaDOS was just waking up and hadn't yet fully regained control of them. Slowly, over the course of the first few levels of this act, she gets more sure of herself, and her ability to alter and mess with the lab increases. The arms presented a number of challenges, the key one being interaction with the player.  It was easy for the player to get stuck behind or inside of the models if they did something too complex. So we had to limit most of the arm action to the walls or ceilings of the test chambers, and we restricted their use on a larger scale to areas where we could be sure of the player's location.

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=== Elevating Videos ===

| With the vacuum tubes such a big part of Portal 2, we designed the new elevators to work within them. We liked the idea that this made the player feel about as important to Aperture as the cargo moving through the tube, and it also gave us plenty of opportunities to show how the system could go wrong, such as when the tube gets blocked, or when cargo rains down on the elevator. The videos began as attempts to visualize some of GLaDOS's dialogue, but evolved into a means of relaying information about the larger world of Aperture. It seemed very likely to us that Aperture would boast to the test subjects about the devices they were testing, and show them the clever ideas they had put into the products. The videos also serve as a reward for completing the test chambers, and a way to make the elevators visually different from one another to prevent repetition.

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=== Faith Plate ===

| The faith plate was originally a robot arm model which we hurriedly placed into the maps to see if the gameplay was fun.  Over time it became apparent that playtesters were struggling to tell the faithplate apart from the standard arm, so we replaced it with a new design. It was meant to be a simple heavy weight which was flung upwards, propelling the player. The length is meant to imply a direction, so the player knows the intended flight path before they step onto it. We experimented with foot marks and treadplates on the design, but it quickly became confusingly busy, so we kept the design simple.

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=== Stalemate ===

| The stalemate resolution button is the earliest configuration of the robot arms we tried. Playtesters enjoyed it, but it took us a long time to find the right place for it in the game. It clearly needed to be defending something, and for a while it defended a paranoid personality sphere who had built a huge encampment of defenses to stop you from getting to him. When the idea for the stalemate button came up, we knew it had finally found its home as part of GLaDOS's last desperate attempt at self-preservation.

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=== GLaDOS Wakes ===

| Originally GLaDOS was built to curl up and disguise herself as one of her rings, potentially explaining how she had survived the explosion at the end of Portal 1.  But this wasn't a very dramatic reveal, so we threw it out in favour of spreading her out over a greater distance. This also made her more recognizable as GLaDOS when you initially crossed the room. The actual wakeup animation was a combination of simulated animation with a layer of hand keyed animation over the top.  A two-stage model was created for this scene. The first stage had separate pieces and connecting cables that would be drawn together by running a physics simulation so that the pieces would interact with the environment. Physics simulations were also used to break apart the objects GLaDOS crashes into while she writhes around.  At the point where GLaDOS rises free of contact with the ground, she switches instantaneously to a fully connected model with controls for hand-keyed animation. From this point, the animator enhanced GLaDOS' awakening by hand, choreographing the violent chaos of her re-emerging consciousness while at the same time conveying the weight of a machine the size of an airliner. Once the hand-keyed animation was done, a final simulation pass was run to animate the cables and dangling parts of GLaDOS' body. The scene was produced very rapidly for an E3 deadline, and a traditional rig for the sequence was never fully realized. This made it difficult when we extended the sequence after E3 to add further animation, but we accomplished it by bearing in mind that GLaDOS herself is pretty broken at this point.  The last part of the sequence requires the player to lose control of their view while being immobilized by a giant mechanical pincher. Once the controlled camera takes over, a careful alignment and time synchronization was required to make all the hand-animated models and camera interact with each other. Each of the stages in this wakeup scene contain a variety of processes that are very challenging to achieve live in a game engine.

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=== Tag: The Power of Paint ===

| Similar to the way the student game Narbacular Drop became the original Portal, the paint mechanics in Portal 2 come from a student game,  Tag: The Power of Paint.  The repulsion gel in Portal 2 is modeled after the bounce paint from Tag, but was redesigned to fit better within Portal.  The original bounce paint always bounced the player at a fixed height and activated whenever the player touched the paint.  We changed the repulsion gel to reflect the player's velocity, such that they will bounce back up to the height that they fell from.  This mechanic lends itself better to puzzles involving portals because players have to think about gaining and preserving height.  We also changed the repulsion gel to only activate if the player jumps off of, or falls on to the gel.  This was done because players would often accidently walk onto repulsion gel they didn't see and then trigger an unwanted bounce.  This was a particularly nasty problem in Portal 2 because the player couldn't get rid of paint once it was applied; whereas in Tag the player can erase paint at any time they want.

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=== Porting Paint ===

| While re-implementing the paint mechanics from our student game, Tag: The Power of Paint, in the context of Portal 2, the biggest change we made was to exclude the paint gun. In Tag, our paint gun allowed the player to paint the environment freely in an abstract outdoor environment, but in our gameplay experiments, that was very difficult to constrain without contrivance in Portal 2's indoor spaces. It also changed the game's pacing significantly, since being able to run at high speed around a level covering everything in paint is lot more fast paced, energetic, and often scattershot than Portal's more cerebral gameplay. Perhaps most importantly, there's a certain elegance in the simplicity of manipulating all the game elements using only the portal gun. Adding a new gun would inherently add complexity and force us to start from square one training the player how to use this new tool, instead of focusing on the game's namesake. Instead, we decided to use the established mechanism of the delivery tubes and have players redirect the flow of the paint with their portal guns. This felt like a good compromise.

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=== Fizzling Out ===

| We needed a puzzle that would demonstrate the different effects that the fizzler has on the game. This map was consistently the one that most of our playtesters would get stuck on and we tried various things to make the puzzle easier to understand. Originally this room had 2 fizzlers in it and was divided up into three distinct areas. This proved to be too complicated and almost none of our playtesters could solve the puzzle. We removed the second fizzler and simplified the layout of the room quite a bit but most of our playtesters were still getting stuck on it. We identified the problem to be the space above the fizzler. Originally this space was completely open, but that didn’t effectively convey to the players that they needed to shoot a portal above the fizzler. We then tried putting glass with several holes in it above the fizzler. This was slightly more effective as players would know that the holes are there for a purpose and would try to solve the puzzle by shooting portals through the holes. The map was still not testing well though, as players could not figure out which side of the fizzler they needed to be on when they shot their portals. We then changed it to have only a single hole through the glass, moved down to the eye level of the player, so that shooting the portal from either side of the fizzler would be a valid solution. This change tested really well and we started seeing most of our playtesters make it through the level without getting stuck on it for a long time.

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=== Emancipation Grid ===

| We originally planned to use the same emancipation grid effect we'd used in Portal 1.  We were surprised to hear during several of our early playtests that players thought this map was the first time they'd encountered one. Players walk through at least one emancipation grid in almost every map.  Playtesters also weren't able to report the grid's properties.  That indicated to us that we needed to better communicate when an interaction was occurring.  Our challenge was to create an effect that was more noticeable to players, but didn't look so solid or so threatening that players wouldn't attempt to walk through it. We chose to keep the cool color scheme, and reinforce the non-threatening nature of the field by mimicking the kind of water caustics you'd find in a shallow swimming pool.  To communicate that the grid blocks portal placement, we added flashes whenever the player shoots one.  To warn players that the grid will destroy objects brought through it, we added a vortex effect that increases in intensity as objects get near. Once these changes went in, playtest feedback demonstrated that players noticed the emancipation grids earlier and had a much better understanding of their function.

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=== Speed Paint ===

| Propulsion gel carried over almost exactly the same as the speed paint in the student game, Tag: The Power of Paint, except that it is slightly more than twice as fast. Propulsion gel combined well with the existing mechanics of Portal, such as flinging, and it also went well with the repulsion gel for long jumps. We had to tweak the player's control on propulsion gel to feel right in the Portal universe, and also added a slight funneling effect to help guide the player when they are speeding into a portal.

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=== Crazy Box ===

| One of the things that the student game Tag: The Power of Paint didn't allow was painting of other objects, since this would have been too trivial in that game.  In Portal 2, however, moving paint around became a puzzle in and of itself, so we began to create puzzles that depended on painting objects. Bouncy boxes and turrets were an obvious choice, and adding this mechanic extended our toolbox to include objects whose basic properties of movement could be changed by the player.

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=== Portal Paint ===

| Portal paint was the last paint we added to the game, and for a long time we weren’t sure of the best way to use it. We experimented with the delivery method and found that it was most effective when it was deployed in large quantities.  Another important factor was the angle of application. Dropping the paint at an angle allowed the player to play more freely with the paint, which gave them the liberating feeling of breaking the rules by being able to place portals where they couldn’t before.

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=== The Ascent ===

| The lake map marks a total reset to the aesthetics and scale of the environments up to this point in the game. You come into the underground cave compressed and as you progress further into the map, your eye is drawn upwards by the elevator tower, sparking cables, falling debris, and finally the test spheres which recede vertically into nothingness. This looking upwards gives the player sense of the vastness of Aperture before GLaDOS and a visual sense of the daunting climb they will have to make to get back to Wheatley. The open areas encourage the player to explore their surroundings and take a break from the intensive puzzle solving of the test chambers.

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=== Project Lil ===

| Project Lil is our codename for an internal push to make our comments more accessible to the whole Valve community.  It was pointed out to us in mail from a fan that in some of our previous commentary, the designers referred unfailingly to the gamer as a 'he.'  Although in natural speech, most of us normally tend to say "they" and "their" rather than "he" and "his," some stuffy overactive minion of the grammar police went through and revised all those usages to make them conform to an oppressive gender-biased rule.  However, research shows that "they" and "their" is a perfectly acceptable and even older form, and we are happy to fall back on it and let people talk the way they normally talk, and screw the so-called rules that alienate our fans.  Thanks, Lil.

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=== Wheatley's As Level Designer ===

| Wheatley's first test was really fun to make because we wanted it to feel like he was a first-time level designer. We see a lot of maps where people try using different textures or lights to write words or put their names on the walls.

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=== WheatDOS ===

| Our initial idea for this version of Wheatley was to replace GLaDOS's eye with Wheatley's, but it wasn't a big enough change to see the difference. Instead we put Wheatley onto GLaDOS's rig, and gave him a puffed out look, like he's trying to make himself look big, using wall tiles.

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