This is a follow-up of the Night Exterior Rendering Tutorial that I have written a while ago, so if you haven’t checked that one already, I advice you to read it before this one.

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.