En:Daylight

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This article should gives some help how to create realistic looking daylight.

Inhaltsverzeichnis 1 Introduction 2 Properties 2.1 Sunlight 2.1.1 Type of light source 2.1.2 Strength 2.1.3 Color 2.1.4 Shadows 2.2 Skylight 2.2.1 Without radiosity 2.2.2 With radiosity

Introduction

Creating a lighting situation that looks natural and communicates the feeling of being outside is not the easiest excercise for a 3D artist. But it's also not as hard as you probably think.

In the course of this article, we will try to create good sunlight by just using stochastic Radiosity. Therefore, no plugins or modules (except AdvancedRender) will be needed. We will also *not* use CINEMA 4D SKY for this, since users of older versions should be able to use this technique, too.

Properties

Good daylight consists of the following elements:

Sunlight

It is obvious that you'll need a light source for the sun. Without sun, there will be no daylight.

Type of light source

The sun is extremely far away from earth, so it is recommended that you don't use a normal point light source, but a Distant light source. This will create parallel shadows, while a point light source would create shadows that allow the observer to locate the position of the light source (making it obvious that it's just a few meters away, instead of some thousand miles).

Strength

Sunlight is bright. Compared to the intensity of other light sources you normally use in your scenes, it probably should be even brighter than 100%.

Color

Sunlight is of a very high energy. Therefore, it should be slightly blue. But since we will also create skylight (which is in fact blue) in this article, it would be better to make the color yellow. Not very yellow, just a bit. Let's say RGB=(255,254,252). Sometimes it's good to disobey reality in order to achieve a realistic impression.
Note that the sun's altitude affect it's light color in reality. The lower the sun stands, the more yellow or even red the light becomes. Try to match your sun's color to the lighting conditions you want to simulate. You can also create a certain mood by selecting the right color: The more yellow/red (warm color) your light is, the more friendly your scene looks. Take a slightly blue sunlight to make your scene look hard and cold.

Shadows

Since the sun is very far away, it is logical that we'll use hard shadows. In fact, it would be more realistic to use area shadows with a very small radius, but in most of the cases you won't see any difference, so it's often not worth spending the render time to area shadows when creating sunlight.
If you don't want direct sunlight, it's different. Image a day with bright sun, but a slightly cloudy sky. The sun would appear diffuse through the clouds, if you look at it. Of course, this also changes the style of shadows from hard to more soft and diffuse shadows. In this case, it's better to use area shadows or soft shadows.

Remember: The more clear the sky is, the sharper your sun's shadows should be.

Skylight

A very imporant but often totally underrated element of realistic light is the light that is emitted from the sky. The sky is blue, therefore it emits blue light. Normally, we don't notice that outside, but you can see it very good in the snow on clear winter days: All shadows are blue. This is because of the blue sky light filling the shadows thrown by the sun.

Without radiosity

If you don't want to use radiosity, you can simulate the sky light as follows: Create a light source (type: Omni) and give it a sky-like blue color. To get a correct blue, it's a good idea to take a photo and pick the sky's color from it. Deactivate the light source's specular light (Light attributes > Details). Then create an Array object and put your light source into it. Increase the array's radius so the light sources are located around your scene. Increase the number of copies to about 12 (or higher) and decrease the light source's brightness. That way (and with a bit more tuning) you can get pretty nice daylight

Anyway, it will look better with radiosity.

With radiosity

The nicest way to make an easy skylight is to create material with only a gradient in its luminance channel. The gradient should go from dark brown to a light brown in the middle. Then go from a bright blue-gray over a greenish blue to light blue, and then to dark blue.

Map this material on a sky primitive (or simply a large sphere surrounding the scene) and switch on Global Illumination. Switch to Stochastic radiosity and set the diffuse depth to at least "2".

You will probably need some test renders until you have to look you like. Control the lighting by adjusting the brightness of the gradient in the sky material, and by changing the brightness of the sun light source. To speed up test rendering, decrease the Stochastic Samples.

After Rendering, you may get a result that looks like the image shown below.