Before we begin we need to setup the lwf.
Go to “Customize”, “Preferences” and click the “gamma and lut” tab.
Check “Enable gamma /lut correction”, type 2.2 in the field next to “Gamma”.
Under “Materials and Colors” check both “Affect Color Selectors” and “Affect Material Editor”.

Don’t forget that for every texture that you use you need to override it’s gamma like in the screenshot bellow:

If you need a more in depth explanation regarding linear workflow, check out my lwf tutorial that I have posted some time ago. However, the steps above pretty much cover the essential.

1)    Click the “create” button and select “cameras”. From the drop down menu select “vray” and click on “vray physical camera”. You can now create and place the camera wherever you want in the scene.
2)    Now we will create the sun. Click again on “create” and choose “lights”. Again, from the drop down menu select vray and click on Vray sun. You can now place the sun and it’s target in your scene.
When you will be asked if you would like to “automatically add a Vray Sky environment map”, click “yes”.

The position of the sun source is directly related to the time of the day. Bellow are 2 examples of renderings with different sun positions (while keeping the rest of the settings identical).

VraySun parameters

1) -turbidity
This parameter affects the color of the sky and overall atmosphere in a way the dust affects atmosphere. A higher turbidity value simulates a larger amount of dust and makes the rendering look more yellowish. See examples bellow:

2)  -ozone – ranges from 0 to 1. Lower values are supposed to make the sunlight look more orange, while higher values should make it bluish. I always prefer to leave this as default.

3) -vray sun size multiplier – a value of “0” produces very sharp shadows, while higher values makes them softer.

4) -shadow subdivisions – if you are using a higher value for the vray sun size you will need to increase the shadow subdivisions as well, otherwise the samples will be visible.

5) -Intensity multiplier – needless to say that higher values results in higher sunlight intensity

Having this said, the settings that I usually use for creating a day rendering are:
-intensity 1
-turbidity 4
-size multiplier 5
-shadow subdivisions 9

If you don’t like the vray physical camera, you can use a standard one as well, but you need to decrease the intensity to somewhere around 0.01

Bellow is a rendering that was done using the settings above.

As you can see, at the moment it looks a bit dark and washed out. You can either play with the curve in vray virtual frame buffer, or start tweaking the vray camera settings.

Vray camera parameters
I always prefer to further adjust the image from the vray camera parameters.
There are 3 main parameters that affect the lighting/atmosphere: F-number, shutter speed, and film speed.

1) F-number
This parameter determines the width of the camera aperture and therefore it affects exposure. Higher values produce darker images, while lower values brightens the images

2)Shutter speed
This parameter determines the amount of time the film is exposed to the light. It is calculated in “inverse seconds” therefore higher values produce darker images.

3)    Film speed
This parameter determines how sensitive the film is to the light. Higher values produce lighter images, but the downside is that the higher the sensibility the more “grainy” the image will look.
For daylight exterior renderings it is recommended to keep this at 100.

There are several other parameters that you can touch (like custom white balance, vignetting, etc) but you can have more control if you do this in photoshop.

In conclusion, even though there are no “universal settings” for the vray camera, whenever I do an exterior daylight rendering I start with the following settings, and depending on the scene I may need to tweak them a little further.

F-number – 7
Shutter speed – 120
Film speed – 100
Rest of the parameters – default.

Bellow is the rendering done using these parameters.

In the next part of this tutorial we will talk about image based lighting, so stay tuned.

Background image
1)    For the first step of this tutorial you need to choose a photo for the background. Try to find a picture that is rich in colors, with shades of blue for the sky instead of black.
2)    Create a plane and place it at the exterior, perpendicular to the camera, like in the picture bellow.

3)    Apply a vray light material, and map the photo to it.

You may ask why you need to map the image on a plane and not simply drop it in the environment slot.; the answer is simple… if you do that, all the reflective materials in the scene will look transparent, unless you use a spherical environment, and not a planar one.

General Vray Settings
Before starting to place lights in the scene, I usually make general rendering settings.
1) Check “on” in the vray global illumination rollout
2) Chose irradiance map with low preset for the primary bounce (you will keep this only for test rendering; this should be changed to “high” before hitting the high resolution rendering) and lightcache for the secondary bounce.
3) Chose “Reinhard” in the v-ray color mapping rollout, with the multiplier to 1.5 and burn value to 0.8

Natural light
The key to obtaining a realistic architectural rendering of an interior at night is the color variation in the light. Many would be tempted to say that an interior scene at night time doesn’t receive any natural illumination; that couldn’t be more false.  Natural light that comes through the window, although it has a lot less intensity than at day time, it is considerably more saturated (in shades of blue).

In order to mimic that effect, the first thing to do is to check the “GI environment (skylight) override”, leave the multiplier to “1” and chose a dark blue for color.
If you do a test rendering at this point, you should obtain a result similar to the one bellow.

As you can see, that is by far not enough. If we increase the GI multiplier we will end up with areas that receive too much illumination for a night rendering. What we need to do in this case is to place a light that will affect ONLY the ambient, without affecting the diffuse or the specular.
We can achieve this by placing an omni light just outside the windows, with inverse square as decay type, and “ambient only” ticked in the “Advanced Effects” rollout.
Use the scale (and non-uniform scale) tool until the gizmo spreads to about ½ of the room, like in the screen capture bellow

For the intensity multiplier, you can choose a value around 0.35, depending on the scene. Regarding the color of the light, choose a hue that is predominant in the color of the sky of your background image, so that it will blend well with the rendering.
After doing these steps, I ended up with the following image:

Artificial Lights
At this point we have enough natural light in the scene, so it’s time to go to the next step. In this interior I will use 3 types of artificial lights: spotlights – that will give a sharp shadow, indirect light (where the wall meets the ceiling) and a smooth light coming from the large pendant in the ceiling.

1) For the spotlights I almost always use photometric lights, so this will be no exception. I started with a “recessed 75 W wall wash” template that comes with 3ds max kit, but you can use any IES file you like and tweak the parameters until you like what you see. In this particular case I have changed the color temperature to 4950 K in the “Intensity/Color Attenuation” rollout and obtained the following result:

2) In the next step, we will add light to the pendant in the ceiling. Since in real life this type of lighting fixture casts a subtle area shadow, the most suitable for the job is a planar vray light. For this interior, a multiplier of 4 and a pale orange hue for color where all what I needed.
I got a bit lazy and did not model this lighting fixture entirely, and I just assigned a vray light material to the part that is emitting light; if I wanted to do everything from a to z I should have modeled the inside of a lamp and use a translucent plastic material for that part in order to obtain a more realistic result (like in the vray lampshade tutorial I have written sometime ago)

3) For the indirect lighting above the wall just model a thin box, assign a vray light material to it and place it above the geometry at the top of the wall. While you are doing this, you may want to “turn on” the monitors by assigning a vray light materials to the screens with a “desktop” map, like in the image bellow:

4) We are almost done and ready for the final touches! If you analyze the rendering carefully, you will notice that it still looks a bit cold, and lacks the “yellow/orange” that is specific to artificial lighting. We can correct that by creating another omni light, similar to the one placed just outside the windows that you have created at the beginning of the tutorial, only this time you need to use an orange tint instead of the blue one.

Here is the final result:

If you have any kind of comments or questions feel free to use the form bellow, and I will be more than happy to respond.

1) Natural light
The first step is to choose a background image of a sky.
For this tutorial I have used the image bellow:

Now put the desired image into the environment slot (3d max’s environment slot, not in vray’s).
In the vray settings, check global illumination, select lightcache for secondary bounces, irradiance map for primary (you could also use brute force, but it will take longer to render).
In the global switches tab, make sure that “default lights” is unchecked.

Last but not least go to the vray environment slot and check “GI environment (skylight) override. In the slot right beside put a gradient (dark blue in the upper slot, a lighter blue in the middle and a pale orange or purple in the lower position)

If you hit render, you will end up with something like this:

2) Adding artificial lights inside
As you notice, it is starting too look like a night rendering, but at the moment it lacks artificial lighting so the spaces look deserted.

We will begin by adding vray lights inside the house, to simulate artificial lighting.
The important thing to keep in mind at this point is that artificial light can look different from one case to another depending on many factors (intensity, color temperature, size of the space that is actually lit, etc.) so you shouldn’t put a light source and instance it all over the place. Be creative and play with parameters like intensity multipliers, filter colors, etc.
For this scene I have used spherical vray lights with intensity multipliers varying from 1 to 2, filter colors with orange, yellow and blue tints and different a radius for each one.

If you hit another render you will end up with something very similar to the following.

3) Simulating artificial light “spreading” from inside
Now we have light inside the house, but the light doesn’t seem to “come out” enough. Therefore we will place vray planar lights just in front of the windows, pointing towards the exterior, like in the following image.

Hit another test rendering and you should have something similar to the render bellow:

4) Adding artificial lights in the courtyard
We are getting closer. What doesn’t look right at the moment is the fact that the courtyard is too dark. Depending on your scene, you may have exterior lighting fixtures (like the lighting posts that I have in this scene), or even exterior spotlights that illuminate the building.  If you don’t have specific instructions for these, you could place lights somewhere behind the camera, so that you give the impression that the space is receiving illumination from neighboring sources (street lights, car lights, or even other buildings).

In this particular scene, adding lights to the lighting small garden lighting posts should be enough.
First I have assigned them a vraylight material with a gradient map; than I have placed vray spherical lights over each one. For each vray light in the courtyard I have excluded the lighting post bellow it. This is kind of a fake, but in the end it looks right, and that’s all that matters. (If you want to do it more “accurate” check out the lampshade tutorial as well).

Hitting a test render at this stage you should obtain something like this:

5) Photoshop touches
a) Add a subtle glow effect to the visible artificial light sources (in this case, the small lighting posts). You can do this using the diffuse glow filter.
b) In a new layer, add a linear gradient from bottom to somewhere at the middle from orange to transparent. Put the layer on “color” and play with the transparency until you like the result. If you are feeling creative, you can also try some subtle brush strokes, with different tints of red, yellow or orange to create diversity.
After having done all of the above, here is the final image.

(CLICK THE IMAGE TO VIEW A HIGH RESOLUTION RENDERING)

Conclusion
Rendering an exterior at night can be very tricky. The best approach in my opinion is to take it systematically by starting with natural light, and adding artificial lights one by one during the process. Otherwise, you may find yourself lost not knowing where you did something wrong.
I can not stress enough how important is to have a few examples of professional architectural photography at hand and look at them at every stage of the process.
Here are some general guidelines that I always keep in mind when I’m doing a night rendering:

1) Even at night time the skylight still casts a subtle shadow.
2) Never make the sky 100% black; it should have either a blue or a purple tint.
3) If there are no artificial lights on the ground, the sky will always be brighter and the ground would “borrow” a bluish or purple tint from the sky
4) The lighting is a mixture of dark purple/bluish tints at the upper part and orange/yellow on the ground and on the building(s). That is because the natural light blends with artificial light sources placed on the ground.
5) The colors are more saturated in a night rendering that in a daytime one.
6) Artificial light sources have a subtle glow around them.
7) If you have “moving objects” in your scene, don’t be afraid to use motion blur. If you know a bit about photography, you are aware that at night time photographers use high exposure times when they target architectural subjects; this causes all moving things around (cars, people, etc) to appear with motion blur.

If you think that I have missed something, feel free to post a comment and let me know.