GDC - Physics in Half-Life 2 93
Their high-level strategy was to invest in gameplay. They decided not to start with a simulator, and to not add features to simulation (until it became necessary). They set out to make HL2 stand apart with the depth and quality of gameplay, as opposed to just 'cool simulation'. This would require a lot of engineering work on tools and design.
A timeline for HL2 Physics:
- They looked into physics demos.
- Demos generated ideas.
- Looked into licensed physics simulators.
- Internalized physics into their design ideas.
- Built a bunch of prototypes and tools.
- Gameplay mechanics experiments.
- Solved technical issues.
- Focused design and tech.
- Solved more problems on the technical side.
- Incremented to deliver a stable system (with valuable features at each deliverable goal).
- A long polish stage before shipping the game.
- Zombie basketball -Satchel charge, trying to explode zombies into nets.
- Watermelon skeet shooting - Watermelons loaded up into an ejector, tossed into the air to be shot.
- Glue Gun - Trying out 'building things' within the game. A gun that placed glue on objects, glue attracted itself to make constructs.
- Danger Ted playset - Glue a model of a designer to a car, glue propane canisters to the car, launch the designer strapped to the car into the air.
- Toilet Crossing - Build a zipline construct with junk to cross a chasm, extra points if you rode on the toilet during the experience.
So, how can they make the gameplay more focused? What ideas are good? How many ideas do they need? How can they measure the difficulty of the gameplay? And, of course, how are the prototypes going to be turned into shippable gameplay?
They reduced design to 'training and testing'. Game design is a set of player experiences that trains the player, allows them to demonstrate a learned skill, and is presented with style. With this criteria, they had an easy way to judge ideas for merit.
Design is also engineering. Defining success, identifying constraints, generating ideas, analyzing solutions, building prototypes, testing results, measuring success, and then re-examining your constraints. Distill out the elements of game design, be creative, but you want a way to analyze your solutions and measure your progress.
This allows you to reverse engineer your experiences. I want them to do 'X'. Okay, what do they need to know before they can do X? Training skills in isolation allows the player to be prepared for future gameplay elements. When something went badly in playtesting, they could look back and see if they'd prepared the player adequately for the experience. If something isn't eventually used, or isn't working, it becomes obvious and can be cut.
Training can have obstacles, though. If the player is in combat or in peril, they're probably not learning. To improve the training experience, you make it clear it's okay to experiment. Sell forced choices tot he player with style. Suggest experiments with the the gameworld. Story should not be an obstacle to training, it should enhance the experience. It's also not distracting like combat. Players can play attention to both. (He uses the example of the sawblades in Ravenholme to chop Zombies in half.) Player value as a metric for skills and knowledge. Each piece of skill must have value, or it gets cut from the game. There is a limit to the total number of things you can teach in a game. You want to cull skills down to the fewest required. Having skills interact makes them both more valuable. Requiring skill from a player makes the skill more valuable to the player. These relationships form a sort of economy, which they refer to as 'design economy'. Allowed a framework for discussion about the process.
Of course, every design has constraints. Objects have to be breakable, with the quintessential crowbar. Physics have to interact with the core combat gameplay. Collisions should cause damage, objects should be used as cover. Physics need to extend the core puzzle gameplay.
Integrating physics turned out to be kind of difficult. Physics are kind of intuitive, but it doesn't "just work". Most designers don't completely understand the technology. Taking the design to the fullest required understanding the simulation. Game logic may place impossible requirements on the simulation. Some elements have to be one part physics and one part game design, fudging the edges.
So, they took on the design interface for the physics. They need to teach the designers about the system (decomposing machines into physics blocks). They needed to become proficient with unfamiliar units and tuning parameters, dealing with a complex set of variables that imply calculations. So, to deal with this they delivered technology incrementally (ramping up the learning curve). They needed a physics expert to support designers.
Some other problems came up, especially in the early days. Many physics engines interact with the game in discrete steps of time. Changes to the state of the system are often queued. Game rules are often discontinuities in state. They also needed to reserve space for 'inventory items' (grenades, etc.) Motion planning is a problem as well (will I hit anything when I go over there?). Collision detection without physics was a required - especially for AI. They ended up building a collision speculator for themselves so the AI would behave intelligently.
This then becomes an over-determined systems, with simulation variables, design variables, and design criteria. The 'Superman problem' - Beating people to death with tin cans. They fixed this by making the mass of gravity gun held items very low, so that you couldn't destroy a car with scrap metal.
Simulation failure also was a problem. Objects get stuck in each other, they don't settle, something that is valid for physics becomes invalid for the design. Simulator 'explosion', game design constraints that can't be satisfied, and creating objects in solid space. Plan for the simulator to fail, and be flexible with your expectations. realize you're going to need to fudge.
To sum up: Engineer to solve gameplay mechanics. Use analysis and design economy to intentionally improve the design. Tech problems remain with phsyics. Some can be solved with design, put plan on investing in the technology. Plan for failure cases and be sure to ask "is this failing as a result of bad design?"
I ranted about this (Score:5, Insightful)
Re:I ranted about this (Score:5, Funny)
No, but you are alone in thinking that someone might read your Slashdot journal (which I imagine is very interesting, insightful, informative, funny, and unread.)
Re:I trolled about this (Score:2)
Even though it takes the same amount of time to do as to post? It's certainly your right to criticize, but if you're not willing to even become part of the community you're critizing, then I can certianly understand why your criticism is consistently criticized.
Plus, if you make an account, you can spend that extra 5 seconds foeing me and never having to see me again. ;-)
Re:I ranted about this (Score:2)
Or at least two of them ;-) Mianly I was lazy and didn't want to spend a lot of time posting something that I had already written, but on the off chance that someone cared, well, maybe they'd share their lottery winnings with me, too. Same odds and all that.
I was there... (Score:3, Interesting)
He then talked about Metroid Prime: Hunters, and again had a live deathmatch between some of the devel
Re:I was there... (Score:2)
Re:HL2 Physics (Score:1)
Re:HL2 Physics (Score:4, Insightful)
Re:HL2 Physics (Score:2)
Atomic-powered torch (Score:1)
Re:HL2 Physics (Score:2)
Like you, the first 10 times you get scared by monsters popping out of the darkness scares you. After that, you start becoming resigned to the fact that the game spawns creatures in areas you've already cleared, making the tactical aspects of the game frustrating.
When I play a FPS, I clear an area, move into that area, and from cover clear the next area, and so forth. Which is worthless when the game just arbitrarily spawns monsters behind you.
Re:HL2 Physics (Score:2)
Re:HL2 Physics (Score:5, Interesting)
The worst part, and what really killed any suspension of disbelief, were the "monster closets". Rooms whose doors look just like a wall, but which open up when you walk by, revealing a tiny room filled completely with as many monsters as it can hold (in the original Doom games, this was sometimes a dozen monsters. In Doom 3 it was usually one or two.) Not just closets, either--these are rooms that could not possibly serve a purpose, other than to hide things to pop out and scare you. It's like they're trying to remind the player that it's just a game.
Also, every out-of-the-way spot in a room contained a monster. ALWAYS. Walk in to a new area, no enemies. Huh. Oh, there are two pillars on the other side. Two zombies behind them, guaranteed. Might as well fire somethign with an area effect at the walls behind them, and get this room over with, even though I havn't "triggered" them yet. Done, next room, same fucking thing. BORING.
Just enough to throw any sense of suspense or anticipation right out the window, but not enough to give me any of the fun 100-on-1 scenarios that made the original Doom so much fun.
Re:HL2 Physics (Score:2)
Re:HL2 Physics (Score:1)
Yeh but I doubt in realy life you'll clear out a supply closet, walk 5 meters, and turn around to see 10 more living guys appeared in the supply closet out of nowhere and are readdy to mess you up something fierce.
I'm sure the occasional room migh
Re:HL2 Physics (Score:1)
i have played it on a freinds computer with normal suround sound.. it isn't the same..
only with quality audio do you realy get that i am scared as shit feeling
Re:HL2 Physics (Score:2)
It seems that with the low framerate I had to kind of "creep" through the game... which, I think, is what they really wanted you to do.
With the high framerate (pretty much replaced most of my computer) I felt free to kind of "run-and-gun" and it lost a lot of the suspense factor.
Friedmud
Re:HL2 Physics (Score:2)
My favorite part is the beginning, up to about 15 minutes' of play past when everything gets zombified. The rest was mind-numbingly dull. Hell was OK, I guess.
Half Life II, which I never expected to be remotely scary, managed to have more and bet
Re:HL2 Physics (Score:3, Insightful)
* Audio work does not require the game engine.
* Modelling the objects and maps does not require the game engine per-se.
* Aspects of the engine can be coded without the physics engine - AI, weapons, Player->NPC interaction, etc
* Other things were going on behind the scenes at Valve besides HL2 - Steam, Creating DOD:S, CS:S, HL:S, etc
Of course, we can't deny that they probably took a
Re:HL2 Physics (Score:2)
And yeah, the gravity gun being a weapon that wouldn't exist without Havok physics.
And, ok, sure. They probably could have done the dialogue without the Havok engine. =)
Re:HL2 Physics (Score:2)
I guess I played a different version of Half Life.
Re:HL2 Physics (Score:2, Funny)
You did. He was talking about Half Life 2.
Re:HL2 Physics (Score:1)
It's 5am, so sue me.
got modded over-rated (Score:1)
Mod-points aren't meant for giving your opinion, replying is for that, mod points are just for trying to get the "better" posts to stand out more.
in the faq [slashdot.org]
Btw I admit this post wasn't so great, but choose the reason for modding me down better!
Re:What the... (Score:2)
Re:What the... (Score:1)
My wife enjoyed it more than I did, she would beg me to play just so she could watch. She said it was like an interactive movie for her, where she could "help me" try to figure things out.
Drunken GDC folks singing karaoke (Score:1)
Winamp compatible stream here [205.188.215.229]
--toq
Re:Hmmm, interesting (Score:1)
There's lots more information at the developer wiki [valvesoftware.com].
You can also get a free version of the modeling/animating software they used, which is called XSI.
http://www.softimage.com/community/xsi_mod_tool/de fault.aspx [softimage.com]
You can't own it (Score:2, Insightful)
You can only rent it, using Steam to grant you permission to play it.
Steam sucks.
Re:You can't own it (Score:1)
I sincerely doubt you are a "legitimate, paying customer," so it really doesn't matter. I refuse to buy games with StarForce attached, because it's genuine malware that treats the customer like a criminal. In contrast, I've found Steam to be incredibly convenient for content delivery --
Re:Hmmm, interesting (Score:1)
I know, I'm mean.
Re: (Score:1)
Failing the leaning tower test (Score:4, Interesting)
Re:Failing the leaning tower test (Score:2)
A five-pound chunk of styrofoam should shoot up above you if you release it while falling. A 5-pound grenade should not.
Maybe (Score:2)
Re:Failing the leaning tower test (Score:1)
Re:Failing the leaning tower test (Score:5, Interesting)
Re:Failing the leaning tower test (Score:1)
Air resistance, anyone?
Re:Failing the leaning tower test (Score:3, Informative)
Re:Failing the leaning tower test (Score:2)
The grenade would fall faster than the person, but not because of density - density doesn't play into it. It's because of less air resistance, which may have a little to do with the density, but a lot more to do with the shape.
Reply:
A grenade made of aerojel [wisc.edu] will fall much slower than one made of steel with an explosive core. Sure, shape is a factor. So is density. Gravity dosen't give a squat about density. Unfortunately the ability of a projectile to penetrate a fluid (like air) does depend greatly up
It's even in Q3 (Score:1)
Projectiles will spawn with the same speed and direction you have when firing them.
It's not on by default though, and I don't think people enable it because it seriously messes up aiming with the rocket launcher.
Things like this... (Score:3, Interesting)
Oh, what a good game programmer could do with an easily scriptable physics engine. Imagine WoW when the spells have effects on the physics, or interact with each other based on their level and element and alignment... I dream of a combination of Mage: the Ascension and Dungeons & Dragons... tell me I'm not the only one.
Re:Things like this... (Score:1)
http://physx.ageia.com/titles.html [ageia.com]
"Warhammer MMORPG"
Its got the MMORPG part, but if you want the magical part you want:
http://www.mightandmagic.com/us/darkmessiah/teaser
FPSRPG Might and Magic game powered by an enhanced version of source, anyone?
Re:Things like this... (Score:2)
Re:Things like this... (Score:1)
There's a reason why the "physics" of WoW, and MMORPGs in general, are very simplistic; synchronizing complex HL2-class (full rigid-body simulation) between several computers in an ordinary multiplayer game is NOT simple... Now try to do it in a game like WoW, where thousands of clients need to have their physics synchronized. It's a daunting task to say the least. The thing
Re:Things like this... (Score:1)
Motion and path simulation (Score:1)
Getting around tended to be more difficult than I'd like to see in a FPS. Part of it was overambition in striving for a truly 3D physical environment, replete with small ventilation ducts and bizarrely slanted ceilings, but I rather frequently found that I needed to jump to get over a 1" ledge or duck to get under a certain threshold, and sometimes both, sadly.
Hopefully this is still a work in process in game physic
Re:Motion and path simulation (Score:2, Insightful)
You realize the fall rates are largely independent of the weight, right Gallileo?
Re:Motion and path simulation (Score:3, Interesting)
If motion in free flight looks wrong, that's probably intentional.
But if big objects bounce as if they're very light, that's a fundamental limitation of impulse-constraint physics engines. All bounces occur instantaneously in such systems. (That's what an "impulse" means; an infinite force applied for zero time with finite energy, leading to an instantaneous chang
Re:Motion and path simulation (Score:1)
"main: no suitable decoder module for fourcc `IV50'. VLC probably does not support this sound or video format."
Re:Motion and path simulation (Score:2)
I've seen this in movie CGI as well as games, so it can't be just down to realtime computational constraints. Most recently in Serenity (the docking clamp on Beaumonde and the final crash sequence both made the ship look far too light).
Re:Motion and path simulation (Score:2)
Yes, and you can also see a helicopter bounce badly in Charley's Angels.
Interesting. So (speaking as a physics illiterate), what is it that's not being modelled by impulse-constraint engines? Compression?
Yes. If you do strict rigid-body physics, bounces take zero time. That's not realistic. There's always some compression. To look right, some compression needs to be simu
Re:Motion and path simulation (Score:2)
Valve created no 'Physics' in HL2 (Score:1)
Re:Valve created no 'Physics' in HL2 (Score:2, Informative)
Re:Valve created no 'Physics' in HL2 (Score:1)
Re:Valve created no 'Physics' in HL2 (Score:1)
HL2 physics is priceless... (Score:2)
Re:HL2 physics is priceless... (Score:1)
Oh, and BTW, I loved the scripted events is HL1, too!
Not so much. (Score:2)
Magic (Score:4, Funny)
Re:HL2 physics is priceless... (Score:2)
Spirit of HL1 (Score:1)
# Watermelon skeet shooting - Watermelons loaded up into an ejector, tossed into the air to be shot.
These remind me of a map I made years ago for the HL1 community project called 'The Spirit of Half-Life'. The map had a number of different 'sport' type activities, including a basketball and skeetshooting games using snarks. Heck I even made it keep score correctly...Ahhh those were the days...
Rube Goldberg© device (Score:1)
Re:Rube Goldberg© device (Score:2)
Re:Rube Goldberg© device (Score:1)
Re:Chaos (Score:2)
My only complaints about halflife 2 ... (Score:1)
If you're going to have an environment where physics are supposed to play into the game, you shouldn't prevent the level completion with invisable walls. If they get there t
New technology? (Score:2)
That's odd, given that Trespasser was released in 1998.
http://en.wikipedia.org/wiki/Trespasser_(game) [wikipedia.org]
Sadly, about all it was used for was naff box-stacking puzzles, with an interface that made stacking boxes extremely hard.