Lighting La Ruelle - Chapter 1 (3ds max & v-ray): Fog/Mist at Nighttime
Before placing a single light in 3d software, it's good to spend a while, looking at the scene, and thinking, imagining a bit. The assignment is pretty clear - fog/mist (damp), at night - that's the 'prime directive'. But that is not all that matters. Composition of the image is important, regardless of the lighting scenario we have to achieve - and that too can influence light placement, strength and color. Visual style and art direction is important also - is it supposed to look real, photo real, stylized? Finding some reference can suggest a few ideas about how to achieve our task. It's also good to think about the technical aspects - is it going to be a still image, or is it for animation, should it render really fast, or maybe we have some computing power at our disposal? But nowadays, when the computers are fast, it's not always that important.
So how does all that theory work in a real life case? Let's take a look at the viewport capture (Fig.01) of our scene. First important things I noticed, were the lamp (marked red), and cobbled street surface (marked red, as well). The street would be a great tool to suggest the dampness, while the lamp would make a nice main light source, especially if it could cast a highlight on the road surface. That lamp would not be enough, so I've decided to suggest more lamps along the street, just behind the archway (that should give us a nice depth in the image), marked blue. Also, I decided to light up some windows. But which ones should I choose? The square one facing the camera (green), or one of the two on the right side (orange)? I don't want any lit windows on the walls facing the camera (marked violet) - that would break the composition that's starting to form in my head, by leading the eye towards the edges of the image.
That still does not cover all the light that should be in the scene. We need some ambient lighting, to suggest we are outdoors. I don't mean ambient settings in the 3d software, but rather the light coming from the environment: sky, moon, distant city lights, that kind of thing. In our case, it should come from above, and slightly from the front. The way I see it, artificial lights should be warm, the ambient neutral, or slightly cold/blue. The final tuning of that balance will be handled in post-production. And we need the fog - this is crucial, without fog all the above would give us a clear night after the rain.
To render the scene, I'm using 3dsmax with Vray. Recent releases of Vray contain a very nice tool - VrayEnvironmentFog. Its main advantage over standard max fog is that it reacts to the light sources, just like real life fog. That means we won't have to fake it by using volume lights and old-style fog - we will work with lights, and let Vray handle the heavy lifting of providing the atmosphere. Note of caution here. While VrayEnvironmentFog can produce very nice images, it also can take a long time to render, especially when there are a lot of light sources, not mentioning the GI. For now in the initial steps it can stay off, we will add it later on.
First thing I usually do, is set the Color Mapping to Exponential (Fig.02). While this isn't probably the most physically correct way, it has some advantages. The way it works, is by preventing over bright 'hotspots', and oversaturated color transitions. It's also very tolerant - it's really hard to whiteout the image, and the lights have a very wide range of usable multiplier/strength settings (but that range often ends up being pretty high, like 512 or so, especially with the fog on). It has downsides, too, making the colors look desaturated, and decreasing the contrast of the image. I actually like it that way, because I can easily bring back the contrast and saturation in post production, and for some scenes it just fits - but if you don't like it, there's HSV exponential mode, which better retains the color. Generally though, I mainly use the default setting with Linear Multiply for rendering some additional passes such as masks.
Next thing was to set up the road surface (Fig.03). A simple Vray material, VrayDisplacement modifier, and we are good to go.
First light I've placed was the spherical Vray Light in place of the main lamp (Fig.04). I started with a very, very saturated orange. I actually did it with the all other lights as well - I have a tendency to use strong, colored lights that sometimes get the better of me. That usually gets fixed in later stages. That first light was duplicated along the stairway, lighting up the way into the image. It took some tweaking of their placement and strength - finally I decided to place them on the left wall, and add one on the right (Fig.05).
Now it's time for the windows. I started by placing a Plane (default type) Vray Light in place of the closer window on the right wall (Fig.06) - kind of by accident really, as it was supposed to be the other window. But that placement gave me a nice illumination of the left building, picking up the bump detail there, so I decided to keep it. I did try the other window, but didn't like it as it lit the arch wall way too much. The same way I lit up the little square window above the arch (Fig.07). A little trick here. As you may have noticed, I use double-sided lights. It's just for preview purposes, as it illuminates the window behind it, giving me a clue that the window is bright - without me having to do it 'the proper way'. It looks wrong, but good enough to experiment with placing window lights, and will be fixed shortly.
Somewhere at this stage, I've turned the fog on. It took me a while to find the right settings - it's good to know general scene dimensions, but it's a case of trial and error (Fig.08). It's worth noticing, that the fog absorbs quite a lot of light, making the image darker than before - and requiring some adjustment to the lights - main light intensity was bumped up to 700.
Another solution is to adjust the exposure. To do that in Vray, we need to use VRayPhysicalCamera, which allows us to work in a photographic manner - setting f-number, ISO, and shutter speed, among others. I aligned it to the original camera using the Align tool - but it still needed some offset to match. After some attempts, I settled on the settings pictured in (Fig.09).
VRayPhysicalCamera also provides the settings for vignetting, very handy even if it will be finely tuned during post production. While playing with exposure, we may continue with a more photographic approach, and change the white balance. When doing night photography, playing with WB can give nice, rich colors in seemingly plain light (Fig.10). I took these photos using Shaded / Cloudy settings, and tried to achieve some of that look in the scene, even if it was a starting to look bit too warm.
To illuminate the fog a bit, we need more light - we need the aforementioned ambient light. But we are not going to use the Ambient setting, nor will we use a Skylight solution. Sky will be handled by a big Vray Light above the whole scene, colored teal (Fig.11), and one smaller Vray Light, angled slightly towards the camera, placed just above the roof. Moonlight will be done using a standard Max Directional light, placed above the camera. Because I don't want the front facing walls to be lit too much, I built a simple shadow-caster object, simulating the other side of the street (Fig.12). For placing such lights, where shadow is even more important than the light, it's good to use viewport shadows display. I use it for almost all lights in the scene, but it really works well with one or two as with any more they tend to cancel each other out.
I didn't want any direct light on the front facing walls, but I wanted to suggest some world off screen. I used three Omni lights, projecting a quickly stitched image of tree branches, to simulate some streetlights hidden behind the trees (Fig.13).
At this stage with the main light sources in place, I took the low quality rendering into Photoshop, and started tweaking a bit. I quickly confirmed that most of the colors were way too saturated, producing an image that was way too warm. Quick try with Adjustment Layers provided the direction I should try (Fig.14). I also noticed that the side walls could use some specularity to accentuate the damp feeling and that there was no nice main specular on the street...
I proceeded to fix those things. Light colors got desaturated and even turned slightly blue. The light coming from the sky was now almost gray.
The lack of specular on the street was fixed by duplicating the main light, turning off Affect Diffuse option, and using the Place Highlight tool to position it in the right spot (Fig.15). Fake? Sure, but looks good, and I couldn't achieve it with the main lamp placed where it's placed in the scene. If it was a real life movie set, it would probably be handled in a similar way by placing a light source just so.
The whole composition was starting to look unbalanced, gravitating towards the right side. I therefore added a light in the doorway down on the street level to the left in order to balance it a bit. There's also an angled box, invisible to the camera, shaping the hotspot to resemble an open door - yet another trick here (Fig.16).
The walls were turned into a Shellac Material, with a VrayMtl in the shellac slot (Fig.17). After some tweaking, I achieved a nice looking, damp wall, catching the highlight from that little square window.
The image was starting to look quite good now but a few tweaks were still required. The metal railings needed a reflective VrayMtl, the little metal roof high above the street needed to look wet, too. But the main problem was my 'preview' windows. I solved that by turning the lights to be single sided, and duplicating them. The duplicate is way weaker, as it serves only to illuminate the wall recession around the window. Now what's behind the window is another fake - it's simply a self-illumination map, using a photo of a window from the outside, at night (Fig.18). It'll do for a still image, but it won't hold up for camera movement - we would need at least some simple interior then. Fortunately we are working with a still this time.
A few more slight tweaks remained - I constantly find something to tweak, even if those things are too small to write about, they are always there. Change the hue here, by a tiny bit, tweak the material there, that kind of stuff. When that's done, we can try to finally render the image at higher resolution. This scene is quite time-consuming to render, due to the fog - overnight is a good idea. For test renders, I use low resolution, fixed image sampling, and lowered subdivs in the fog.
Again, note of caution - Fixed sampling produces a lot of bright noise in specular areas appearing as though there should be nice, crisp detail when you do a full render. Much of this disappears and gets filtered down and smoothed, providing a much softer looking result in the end. This is something to bear in mind and so be prepared to do more than one higher quality render. The image took 22 hours to render, but I used a 3-year old machine.
Most of the post-production I had already sorted out, throwing my test renders into that first PSD test-image. I used a few radial gradients to enhance the atmosphere, some color corrections to bring back the cold, blue hues, upping the gamma a bit, overlaying some photographic smoke images, some subtle chromatic aberration - simple things, really, but as always, crucial to a good looking image. (Fig.19) shows most of the things I added. The final image is on (Fig.20).
I'd like to point out that this image does not use GI. Sure, it wouldn't do any harm but it works quite well even without it, mainly due to the fog which adds some bright fill to the scene. Apart from this it's nighttime whereupon the bounced light is way weaker than during the daytime (no sun, no bright sky).