Star Citizen Live: Let There Be Light

The cubemap or the environment probe is the absolute fundamental part of our lighting workflow. Without it, we've just got basically a pitch black interior. It's pitch black because it's all interior and hidden away using vis areas and stuff, which basically means that you start from absolutely zero lighting. And what an environment probe does is you place kind of like an area of effect. In this case, these are all kind of cubes with a little bit of softness on them. And what they do is they capture what's called a cubemap, which is just a texture which is captured from, imagine that each one of these has a little camera pointed in all six directions of the cube. It takes a screenshot and then reprojects that ambient light into all four directions. So the more that you have, theoretically, the more detail you can get in your ambient lighting. These are generally approximations. So for example, on this side of this bed over here, it's actually receiving the light from this cubemap. So if I turn that one off, then it gets more lighting from this cubemap and vice versa.

Well, without them, and unfortunately still not having any ray tracing or something like that, you need ambient lighting in the game. A long time ago, you would just have a consistent ambient value, which would be some kind of gray or blue or taken from the sky color, so I don't know, some kind of orange. And that would just be projected throughout the entire world in a uniform way. But cubemaps allow us to account for occlusion based on the window, for example, or the ceiling or the floor, which makes things then appear darker, which gives you more depth of contrast between the interior, which is nice and dark here, versus the exterior out there. And the brighter it gets outside, I'm not sure how easily some of this will pick up on stream, but the brighter it gets on the outside, the cubemaps will recapture. And then you'll get even more light spilling in. So if we don't have any lights at all, you get already this nice base ambient lighting look. And if you want to actually see the cubemaps, I can turn on this little debug mode and I'll turn off the screen space reflections. So this is basically all of the materials just turned into a glossy kind of chrome mirror, for example. And this shows you what each of the cubemaps' reflection maps are picking up. So obviously towards the windows, you're getting a lot of this exterior lighting. And that's getting reprojected into the room. So when I turn it back on, you can see these highlights coming in on the more reflective surfaces. And this is without any additional lighting whatsoever. So this is just the base kind of ambience.

Yes, exactly. So for example, especially for demonstration purposes, we want it to look as good as possible. So I'm turning on shadows quite often. But probably, I guess, 80% of the lights that we're placing generally don't cast shadows. And the basic thought process there is that if it's some kind of ambient light or it's just acting as a fill for the environment, you don't always need to have shadows turned on. For example, let's say that this was quite bright. Let's make it a little bit brighter. This is again one of those things where, when you don't have ray tracing and the methods that offline renderers use, you have to fake a lot of things. In this example, there's no bounce light coming from this light here hitting the floor and then shining back up. If I turn it off and on, there's no difference in this part of the frame. What we'll do sometimes is we'll add a bounce light or a fill kind of light. And in this case, I'll just extend the bulb a little bit so it's a bit softer. I'm thinking that I want the light source to be about as big as the cone of this light hitting this pile of dirty laundry on the floor. So I'll bring that down to about there. And then lighting is pretty much all about ratios. So it's all about how bright is your key light and then how bright are the subsequent bounce and fill lights and that kind of stuff to create contrast in your scenes. So right now this fill light is just way too bright. So I'd bring that way down, and probably even more than that. And so now it's very subtle, but it just adds a little bit of that greenish light bouncing up into the ceiling and against these areas. And this light, because it's so subtle in the grand scheme of things, it doesn't need shadow casting, to go back to your initial point. Key lights, shadow casting. Fill lights, no shadow casting.

It's always a hard balance, because in an ideal situation, of course, every single light would be shadow casting and ray tracing would be on everything. You take it to the point of looking awesome, and then you often have to scale it back by degrees to get to the point where it's performant.

Yeah, exactly. I mean, obviously, we try and replicate the real world as much as possible. And in the real world, I'm not sure I've heard of a light source that doesn't cast shadows. That would be interesting. So that's obviously the goal. But then the realities of computer graphics tend to get in the way of that sometimes.

From an artist's perspective, we don't control the exposure itself directly. We control the exposure through how bright we make our lighting. In the background, we have this auto exposure system, which has a maximum brightness range and a darkness range, and then it tries to strike a balance in between. So I've got these buttons up here which will let me force the exposure to a certain, almost like an f-stop, but it's actually an EV value, an exposure value. So this, for example, I've got it locked to an EV of 10, which works fine outside, and then once you get inside, the darker areas start getting really, really dark, almost pitch black. And so without it, the auto exposure can kick in and then lift those areas. That's how you get blown out outdoors. Then when you're outside looking in, you'd get darker looking interiors from a distance until you enter them. That's how we work with our dynamic range, but we don't actually have any individual control, like say if I wanted this room specifically to be a certain exposure brightness, I don't have that control. Which is fine because we have so many locations in our game. Having that extra level of control just means more time tweaking, more opportunities for bugs to appear, that kind of stuff.

Yeah, exactly. I mean, in this case, maybe I'm doing something for a cinematic. So the pipeline or workflow for lighting a cinematic is very different from what we would do in the PU. What we try and do is make our characters look as good as possible all the time, but the difference between a movie and a game, the primary difference obviously, is that you can move around, you can come at a character from any angle, and therefore the artist doesn't really have any true control over how the character looks. In a movie, everything is set up very, very specifically in every single shot, and lights don't generally make sense. They're just placed in space around, reflected, that kind of stuff. For lighting a game, if this was a game character that we were doing, this light rig probably wouldn't work, and I would have to unfortunately kill everything I've just done, weep a little bit and then start again. And in this case I would try and find a way to motivate that light from the scene, so I'd pick a direction, so maybe he's got some lights hanging off of his thing here, and then I'll try and see if I can make something like that work. This gives him a bit of a mysterious, don't-want-to-mess-with-him vibe. And then again, luckily, because it's a sci-fi game, we can justify having lights in places where most people wouldn't actually put lights. So if I put a light on the floor, like how I had in the original lighting setup, you can have something down here, and now, if this was in-game lighting, it would be a little bit closer to something like this. And then we can tweak things a little bit more. We just have a little bit less of that really fine control. Specifically with putting in an eye catch light for the specular highlights on his eyes, that's a lot harder to motivate in an actual level design sense of lighting.