Cinema 4D / BodyPaint 3D Program Documentation Tutorials Light and Shadow Tutorial Lighting Fundamentals Visualizing Interiors
Function available in CINEMA 4D Prime, Visualize, Broadcast, Studio & BodyPaint 3D

Lighting

Now that the materials have been created and assigned we will illuminate the scene. Since this is a day scene and no interior lights will be turned on, the main light source will be the sun, whose light will shine through the window. We will begin by creating the sky and the sun, after which we will simulate the dispersed sunlight by creating additional light sources.

You can either continue working with your own room scene or use the already textured scene provided with the tutorial:


Physical Sky

Almost all exterior and even some interior scenes require the use of sunlight and the depiction of a Physical Sky. For the latter we could, of course, use a simple image but a more practical method of creating a sky is to use the Physical Sky object, which lets you define season, time of day and even the type of weather. The Physical Sky object also envelopes the entire scene, giving you the freedom to view the scene from any direction. Create a Physical Sky object by selecting it from the Create | Physical Sky | Physical Sky menu. As is shown in the image below, this object offers numerous options in its Basic menu alone. You can also load presets for sky or weather types. The options at the bottom of the menu can be enabled or disabled, depending on the properties you want to include.

For our scene, we will only enable the Sun and Sky options. The settings in the Time and Location tab let you define the time of day, season and even your location on the earth! These settings will affect the sky’s gradient colors and the location of the sun. You can also rotate the Physical Sky object around its Y axis in the Viewport in order to position the sun to better match your scene. Configure the Physical Sky object in such a way that the sun shines through the room’s window at a steep angle onto the floor. Use the image below as a reference:

You will surely have noticed the blue tint the room now has. This is due to the color of the "sky light", i.e., the light generated by the sky sphere itself. This light casts no shadows and permeates all areas of the room. This can be very useful for exterior scenes but creates an unrealistic look in interior scenes. This light’s brightness can, however, be adjusted via the Sky tab’s Intensity. For our scene we will reduce the "sky light’s" intensity completely to 0%. As can be done with the Sky, the sun’s intensity, color, shadow type and other properties can be adjusted using the settings in the Sun tab. The image below shows the setting for the Sky and Sun tabs:

The next image shows what the scene looks like after the Sky intensity has been reduced to 0%. Here you can clearly see how important the reflective properties of a material can be. Even though only a small area of the floor receives light, several scene objects contain reflections, which help us determine which surfaces are smooth or matte and helps us better differentiate objects.

Sunlight reflected from the floor

Next we have to disperse the sunlight reflected from the floor throughout the room. We must also simulate the light from directly outside of the window that is also reflected into the room. These additional light sources should cast no shadows and should not generate any specular highlights. First, create a new light and position it beneath the floor where the sunlight hits the floor. Since this light will cast no shadows it will also illuminate the room through the floor. Positioning the light in this manner will automatically widen the light’s cone into the room letting us, for example, also illuminate the walls directly above the floor. If we instead used an Area light and placed it slightly above the floor we would not be able to illuminate the walls because this light that this type of light emits falls off very quickly at its sides.

Set the Type option of the light you just created to Area, place the light just below the floor and orient its Z axis towards the center of the ceiling. Use the image below as a reference:

The Contrast value in the Details tab can be adjusted to make the shadows softer and more diffused, independent of the illuminated objects’ material settings. This should generally be done in situations in which multiple light sources are used within a small area. The result is shown in the image below. Although the light primarily illuminates the ceiling above the window, the light also reaches areas throughout the room, making almost the entire room visible. Modify the brightness and color of this light to match that of the sunlight hitting the floor.

Light reflected from the ceiling

Next, we will again reflect the already reflected sunlight - this time from the ceiling deeper into the room. Create a new Area light - again without shadows or specular highlights - and position it above the ceiling. Angle the light so it points towards the floor in the area of the camera. Use the image below for reference:

We will give this light source a slight red tint, which will help accentuate the light reflected from the numerous red surfaces in the scene. This light’s Intensity should also be much weaker than the previous light or the sun itself. The intensity of the light reflected from the walls of the room will steadily decrease the farther it is from the window. The remaining settings can be taken from the sample image above. We are mainly concerned about the size of the rectangular Area light - use the handles to scale the light to match the size of the room. Adding this light has diffused the room’s overall illumination.

The second window

If the model of the room is viewed from outside you will see that a second window is located on the wall opposite the window through which the sunlight is shining. Of course sunlight cannot pass through this second window like it does through the first but dispersed light from the sky can. We will use two light sources to simulate this light. The first will be an Area light positioned under the floor at the end of the room at which the camera is located. This light will be given a light blue color with a low Intensity value and will be angled towards the ceiling. This light can be seen at the left in the following image - its settings in the General tab are also shown in the screenshot below:

In addition to brightening the ceiling, the surfaces facing the viewer, e.g., the sofas, are now illuminated as well.

An additional light source will now be added to simulate the light that runs parallel to the floor on the same side. This light will penetrate deeper into the room and will have a greater intensity. You should be familiar enough with the light settings to make a detailed description of them redundant by now. Use the image below as a reference for positioning the light and modifying its settings. At the bottom right of the image below a rendered version of the scene with the new light source is shown.

The region around this brightly illuminated window now appears a little too bright but we will take care of this later. What is important now is the positioning of the lights to avoid any unnatural-looking or incorrect shadows.

Light reflected from the walls

Currently the light is emanating vertically between the walls that contain the windows. In order to include walls with no windows in the lighting equation we will add two more Area lights that will be positioned outside of and parallel to the windowless walls. The image below shows one of these lights after being brought into position. Position a second light identical in size and intensity outside of the opposite wall.

These lights will also be given a slight red tint and will not generate specular highlights. Since these lights only server to create diffuse light in the room, set their Intensity to 50%, as shown in the image below:

As the test rendering below shows, parts of the room are far too brightly lit. This is a typical result of using numerous light sources to illuminate a scene such as ours. We could remedy this by reducing the intensity of each light source accordingly but Cinema 4D offers its own solution, which we will demonstrate later.

Shadows

Due to the fact that our scene contains so many lights pointing in different directions we have purposely not cast any shadows - yet. Parts of the image, though, do not look realistic without shadows. For example, the column in the center of the room and other objects that lie in the path of the sunlight should cast shadows. Since the room is already too brightly lit we will not create an additional light to create these shadows. However, none of the existing lights is positioned correctly to cast shadows in the right direction. In such an instance a light source can be defined to serve as a "shadow caster" only. Such a light will not illuminate the scene but will only cause shadows to be cast.

Create a new Area light and position it between the window through which the sun shines and the column. Angle the light slightly towards the ceiling. Set the Shadow type to Area and enable the Shadow Caster option in the light’s Details tab. Also enable the Z Direction Only option, as shown in the image below, which will ensure that the light will not illuminate any objects behind it.

Because the room is still so brightly lit you should turn off some of the existing light sources when making test renders. At the top of the image above an example is shown for the placement of the shadow-casting light; at the bottom of the image is a rendered version of the room, including shadows cast by the new shadow-casting light. Wen done, don’t forget to turn on any light sources you turned off for test rendering.

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