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Deus EX: Invisible War - Dev Diary#2 Feature
Chris Leyton
13/02/2004
Brian Sharp, Sound Programmer on Deus Ex: Invisible War explains the concept of sound and physics integration...
Following on from last weeks first Developer Diary, Eidos and Ion Storm have once again provided us with a new diary; this time around focusing on what goes in to creating the music score and sound engine within a game like âDeus Ex: Invisible Warâ.
Brian Sharp is the man responsible for bringing the sound to life in âDeus Ex: Invisible Warâ, in his piece we learn about how sound is created and more importantly how it merges with the in-game action.
The DX:IW Sound Engine
There are upsides to being the sound engine programmer. I get a nice surround-sound system in my office, an office that I have to myself most of the time, because my testing often involves loud placeholder sounds, honking noises, screeching static, or the same 3 seconds of dialog played, back-to-back, for ten minutes straight, until it doesnât even sound like human speech anymore.
But, alas, it was not all peaches and cream and ear-damaging static. We had some challenges to tackle: Notably, we used the physics engine Havok, and needed our physical interactions to sound as good as Havok made them look. Also, we had a legacy to live up to â“ Looking Glass Studiosâ legacy with the original Thief sound engine. So we put a lot of time and energy into making sure that the sound engine for Invisible War (and Thief 3) was up to the challenge.
Physics-Sound
Our Havok-powered physics in Invisible War are a pretty big step from what weâve had in the past. Objects can spin and slide and roll and bounce and clatter and, generally, interact in far more elaborate ways than ever before. But it begs the question: what do all those interactions sound like? Havok does a lot of stuff, but this particular question it leaves unanswered.
A crucial component of our physics-sound system was giving as much control as possible to the sound designers. Theyâre the ones who will be putting the sounds in and tweaking them, after all. So, our final system gave them the abilities to hook up different sounds for objects sliding and rolling and bouncing and crashing against one another, and to differentiate the sounds based on the two objectsâ materials & weights. Furthermore, they could special-case sounds for specific objects, if they wanted, since a bullet hitting a wall doesnât really sound like a generic âlight metal objectâ hitting the wooden wall. Then, finally, we had knobs to adjust the pitch and volume of the sounds based on how hard objects hit each other, how fast they were rolling, and a host of other parameters.
For the first implementation of this system, I got our sound designers to record themselves just speaking the words âBounce!â and âCrash!â as well as âRollâ and âSlideâ, with the âoâ and âiâ looped, respectively, so I could draw them out for particularly long rolls and slides. The end result was a great proof of concept and also pretty hysterical, as youâd knock over a barrel and hear a cacophony: âBounce! Bounce! Crash, crash, crash! Rooooooollllllllllll⦠Sliiiiiiiiiiiiiiide!â Surreal.
When I handed the reins over to the sound designers, they were rapidly able to plug in sounds that sounded fantastic â“ much better, unsurprisingly, than the spoken placeholders. Empty metal kegs were the favorite early test object, since they made great hollow, reverberant banging and rolling noises as you threw them around a little test level. With time, we plugged in sounds for all the different kinds of collisions that occur during the game, and in the end, it worked out fantastically. Throw a heavy metal chair against the wall and youâre rewarded with a great solid âthunk!â and a grinding noise as it scrapes the wall as it falls to the floor. Throw an unconscious guardâs body down a flight of stairs and wince as he thuds and thumps realistically all the way down.
Propagation
So now we had our collisions making noise, but how does that noise reach your ears? How does that noise reach guardsâ ears? The original Thief games made use of Looking Glassâ proprietary sound engine, which modeled propagation, the effect of sound moving through the world in an accurate manner. Many games, including the original Deus Ex, allow sound to go straight through walls, and just get quieter over distance. So when you, the player, close a door, it doesnât actually affect your ability to hear that guard, the one on the other side of that now-closed door. And, significantly, it also doesnât affect his ability to hear you. Sound goes both ways, after all.
Well, we wanted to make sound a more important part of the gameplay this time around, so that wasnât going to cut it. So a big part of the sound engine for Invisible War is a propagation system very similar to the one used in Thief 1 & 2. If youâre standing directly above a guard on a floor below you, and you say something, your speech has to make it down the hall, down the staircase, and back up the hall on the next floor down if that guard is going to hear it. Sound can pass freely through open doorways, but if you close a door, the sound on the other side suddenly gets much softer, if itâs a solid door. Frail or battered doors wonât block as much sound, and solid metal doors might block all sound entirely when theyâre closed. Windows block less sound than doors, generally, but if a window is shot out, well, sound passes through unabated. The point is, it works the way youâd immediately expect it to work.
The important thing is that a player is provided with enough information and consistency to be able to make intentional choices that the game doesnât thwart. If youâre going to blow open a chest with a grenade, you know the guard nearby will hear you, because grenades are loud. If you shut the door and itâs a good, solid door, you have a good chance of blowing that chest open without alerting the guard. Plus, if youâre not sure how solid the door really is, you can close the door and listen for the guardâs footsteps or speech, and you know that if you can still hear him clearly, he can hear you clearly, too.
A nice side-effect of propagation is that the sound follows a real path through the level, so if youâre listening for someone saying something, you hear the sound coming from its âlast bounce,â so to speak â“ if the sound path goes through that doorway over there before hitting your ears, you hear it coming from the doorway. I had some fantastic experiences playing Invisible War in my office at night with the lights off and the sound cranked where I would stealthily lie in wait in a dark corner of a room, listening for an enemy to make some noise, and follow the sound to find her â“ or run the other way if I was trying to avoid her!
In one particularly spooky experience, I thought I had cleared out all the enemies on a level, and I was making my way back out by climbing around through the ceilings. Suddenly, I heard the clanking sound, far in the distance, of someone walking on the metal floor in boots. The slow pace of his footsteps told me that he wasnât alert â“ he didnât know I was there. Otherwise he wouldnât have been strolling around so casually. So I crept slowly around the pipes and upholstered ceiling, following the sound of his footsteps through the vents connecting the rooms, making sure to creep so slowly as not to make any sound. Gradually the sound got louder and closer, until I crept into a room and saw a parka-clad Templar guard pacing slowly around on his patrol. I pulled out my sword, dropped behind him like a silent, deadly ninja, and dispatched him in one quick swipe. He never even knew I was there.
Remember to keep an eye out for next weekâs Developer Diary, when weâll bring you further insights into the creation of a landmark title such as âDeus EX: Invisible Warâ.
âDeus Ex: Invisible Warâ is scheduled for a European release on March 5th, 2004.
