Two weeks ago we we posted some screen shots of the new marines in Natural Selection 2. We were really happy to hear the overwhelmingly positive response to the new marine design.
There were a lot of comments and questions about the renders we posted, so this week I put together a video to show all of the components that make up the rendering system in our engine.
Here's what you're seeing in the video:
Wireframe – This shows the geometry that make up the objects visible in the scene. Here you see about 100,000 triangles. Each marine has over 13,000 triangles!
Normal Map – In addition to all of the geometric detail in the models, we get even more detail by using a normal map. The normal map causes flat triangles to be lit as if they were actually more complicated surfaces (here's a good explanation from our friends at Wolfire). For our models, we generate the normal maps from incredibly high polygon meshes.
Texture Map – The texture map is a hand painted image that specifies the color of the models.
Specular Map – The specular map is also hand painted and tells the rendering engine how shiny the surface is and what color the reflected light should be. For metals this is typically similar to the surface color. For the skin, we use a blue tint to counteract the warm tones of the texture and give the result cool white highlights. The cloth parts are completely black so that they won't be shiny in the final image.
Gloss Map – The gloss map also helps define the shininess of the surface, but in this case it's how smooth the material is. For a really smooth surface – like a pool ball – the highlights will be very tight, but for rough materials it will be broad. There isn't too much detail in the gloss map because this effect tends to be fairly subtle.
Lighting – To determine how bright each pixel in the final image will be, the rendering engine computes a number of lighting passes. Each pass uses the normal, texture, specular and gloss maps to figure out how much light is reflecting off the surface and entering the camera's lens. Here we're just showing the lighting passes without the influence of the texture map for clarity. Shadow maps are also used to determine which parts of the scene should be in shadow, although not every light casts a shadow for efficiency.
Ambient Occlusion – The rendering engine applies a screen space ambient occlusion technique to add even more shadowing detail. Ambient occlusion is a measure of how much light from the environment is blocked by nearby surfaces. We use a simple approximation to darken the crevasses that aren't handled well by the shadow mapping system. The ambient occlusion is applied as a darkening effect over the final lighting; this isn't physically based, but gives us the results we're after.
Combined – Here the lighting and texture mapping are shown combined. In practice this is actually done during the lighting passes.
Atmosphere – The atmosphere pass simulates the effect of light hitting tiny particles in the air (here's another example). This has become one of the "signature" effects of our rendering and you can see it put to extensive use in our other videos.
Color Grading – Also called color correction, color grading is the process of adjusting the brightness, contrast, color levels, etc. of the final image. This gives a lot of control over the scene that can be difficult or impossible to achieve by tweaking the lighting and texture maps.
We hope you've enjoyed this "under-the-covers" look at our engine. You can also see our rendering engine at work (with motion blur!) in the teaser video we released on the main site.
We have our heads down around the office here, cranking away on some important deadlines, but we wanted to give you guys a little something while you wait. So, here's an environment concept painting put together in wallpaper format. In it you can see the central drilling room, one of the landmark areas in a mining map currently being worked on. This is one of several maps in the overall Refinery themed set.
Enjoy!
We decided we wanted to try motion-capturing the marine animations in NS2 because there are tons of them to make and because they are very time-consuming to create (because the human eye is so familiar with how humans move). Colin Knueppel is one of two animators on NS2 and has done motion-capture before (unlike the rest of us). He wrote up with this set of guidelines to help us get started. We thought this might be helpful for other game developers and interesting for everyone.
Check with the mocap studio
Motion capture most often uses a myriad of cameras to catch reflective balls sticky taped or velcroed to an actor's body. If you bring something similarly reflective.. well, it can cause issues. Discuss what you'd like to bring with you to the studio with the studio. Ask them what you can do to minimize any conflicts your props may cause.
Have some masking tape
Hopefully they'll have it there, but if they don't, have your own tape. Putting down a target from start to finish helps. We animators can dampen or ramp up motion to make a target move X far or turn Y more, but the closer to the mark they get, the less work we animators will need to do.
Send the actor lots of Marine concept work with notes
The better the actor understands what his character is wearing and what restrictions he may have, the better the performance will be.
Bring the material with you
Unfortunately many actors have been disappointingly unwilling to read material sent to them, preferring to "wing it." Setting aside 45 minutes before you're on the mocap clock with the actor to make sure they understand what they'll be doing is preferable to arguing it out while the machines are running. If you can set aside an afternoon to plan through moves with him or her before the mocap, even better. Inside the mocap studio your on an expensive clock. A parking lot with coworkers to get down the gist of motions is a great start. Getting time with the actor to convey what you learned will cost you the actors wages, but the motion capture session will go many times smoother.
Proper weight
A marine tends to carry something akin to 60 lbs of gear, ammo and armor. Weighting the mocaper down correctly will keep him from doing unrealistic motion, give his foot steps proper weight and dampen the slight dancey tendencies that come with mocapers. It's not their fault, usually. It's human nature. When you don't properly weight a character, the actor often hams it up to "act" bigger or more impressive. It may work on film, but the cruel eye of the motion capture cameras will make every odd mannerism twice as goofy. Ask the motion capture studio what you may be able to use to properly weight the character. A belt with some sand bags attached to it, a shoulder straps with some weights, some ankle or wrist weights. Get or make a well-weighted weapon. Find out if there's a color you should use that wont throw off the capture.
With each of these, we don't necessary want to go realistic but light of realistic. Ask the actor what he'd be comfortable with. Test it ahead of time when practicing with the actor, if you can.
Recoil
An innovative approach to motion capture was tested by my lead at Bioware, Shane Welbourn, and it worked fairly well. Gun recoil comes from the gun, not the marine shrugging spasticaly. When the actor is "firing" have someone strike the rifle's end. This makes the motion driven by the gun, not by muscle contractions in the actor.
Make it as realistic as you can
Ultimately the less the actor has to guess, the more realistic the motion will likely be. If you can restrict his spine movement, he'll compensate for the marine's rigid outfit. If you tape a mocap friendly ruler to his forearm, he wont have to guess where the pad will be. If you give him a nicely weighted weapon that's approximately the right size, he'll wield it right.
Experience
Find someone that has "been" what you want to mocap. Finding an actor who was a marine, he'll bring his experience to the session. When you get someone that isn't familiar with appropriate motions, they sometimes bring their other non-related experiences to play. We had a martial artist being dual-booked for our sci-fi game that could not, if his life depended on it, make a kick that didn't go at least a foot and a half off the ground by the time it was finished. That flourish took hours of animation and creative camera work to tone down.
Getting an appropriately experienced actor is not without pitfalls. Sometimes what actual marines do is less interesting then what we think they do, and even a hardened marine can come across with oddly consistent emotional gestures. Meeting the actor is a good way to pick up on problematic gestures, and practicing and discussing the moves ahead of time is a good way to avoid uninteresting motions.
Do what looks right, not what is right
This is a huge, but sadly not well known, rule of animation. The human mind has expectations, some of which are not always true. When confronted with whether to do what looks right or what is right, always go with what looks right, because an audience is not going to have the benefit of an explanation. They will cock their head and say, "that's odd." We want to keep the player in the game focused, not educate them.
We hope you found this interesting and helpful and we're hoping to share with you some footage of our motion-capture session!
As the third part in our alien "reveals", we give to you, the Gorge!
The Gorge probably has the most character of any of the aliens and we knew we wanted to preserve is his slightly pitiful, hard-working and heavyset character (never say fat, it's rude).
Being the main builder/healer class and without much offensive power, we thought his pudgy visage needn't say "I want to eat you" but instead, "No one appreciates my slime-piles". Hence, the defeated look of his half-closed eyes. His semi-awkward face armor implies that he needs to stay safe more than he needs to attack fast-moving targets and the upturned armor "ears"...well, they're just cute.
His glowing spare tire ties him into the hive somewhat, in that both play a key role in the team's abilities and advancement. Here's the finished model and texture:
Here's a video showing him in all his swollen glory:
Spit
As in NS1, the Gorge can spit a projectile that does damage to marines and structures. It makes a sizzling sound on enemies and glows, doing damage over time. It also obscures marine players' screens a bit and slows marine movement for a short time. It shows up as a bumpy infestation on its target. Spit alt-fire is a shorter-range, slower speed, more potent version especially suited for structures.
Health Spray
We're keeping the healing spray from NS1 as well. This creates a cloud of healing bacteria that will heal all friendly players and structures within it. Using this he'll be able to keep his teammates and precious structures alive and healthy. The area effect also means he won't have to move his corpulence unnecessarily.
Damage Soak
One new ability we're giving the Gorge is a armored protection ability (name pending). By holding crouch, he can drop his cushy paunch to the ground, extend the armor plates on his back. Doing so will mean that he takes damage off his energy instead of health, as long as he can do so! Energy is like the equivalent of alien ammo, but it never runs out and is always replenishing itself. So if he goes immobile, he can soak quite a bit of damage without getting hurt. At some point though, he'll run out of energy and he'll need to be saved by other players or will need to get up and shuffle away. You can see this ability at 0:32 in the Gorge video.
Geeky gamedom anecdote: if you played the celestial Star Control ][, you'll recognize this ability as similar to Utwig's special ability. We are toying with having the ability give you energy when it soaks damage as well, and reducing energy when using it without actually taking damage. I think it could an interesting Yomi layer.
Chambers
Chambers and how they relate to alien upgrades represent the weightiest change for the Gorge in NS2. Now there is an Alien Commander building technology structures, so Gorge-created structures won't unlock upgrades or abilities for other players. The unctuous chambers that the Gorge spits up will be purely tactical. These include the familiar Defense Chamber (automatically heals players or structures nearby) and the Offense Chamber (a kind of organic turret that shoots spikes, possibly renamed to Spike Plant). His overabundance...of abilities mean we'll probably limit his structures to these two.
One last ability we're considering is one suggested by the community - by holding shift he could Belly Slide along slick or downhill surfaces. Maybe as a quick escape down a ramp or just for fun?
We're hoping that these abilities will make the Gorge a fun class that straddles the line between attacker and defender and gives him lots to do near combat and in alien bases. He'll never be much of an attacker, but this butterball is the team medic and engineer and thus, deserves to be loved (by anything with slime on it at least).
Next up is the Lerk!