We can also use the Sky Dome Light to light the interior. However, this light is designed for outdoor scenes that require illumination from multiple directions. It assumes a spherical dome in the horizon of the scene and the objects will trace rays to sample the light. In an interior most of these rays will hit an object, getting no contribution at all. If using it to light an interior you will get a lot of indirect noise in the scene and therefore it is not advisable in most cases.
This light is designed for outdoor scenes and is represented by a spherical dome in the background. Multiple importance light sampling will trace rays to specific directions of this dome. However, in an interior scene most of these rays will hit an object, getting no contribution from the light at all and thus creating noise. In this situation, adding light portals to the windows will help to reduce noise in an interior scene when using Skydome lighting.
- Create a Sky Dome Light.
The following images show the Sky Dome Light with the Color set to white. With the Sky Dome light samples set to 3 and the GI Diffuse samples set to 8, we get a cleaner image.
We can also light the room using a HDRI. This can give a feeling of natural lighting in the room. Some HDRI's work better than others in this type of interior lighting situation. You are better off using a HDRI that has strong sun light in order to give you better directional light coming through the window.
- Create a file texture and open the HDRI. In this case a HDRI with a strong directional sun light has been used. This will give us stronger, sharper directional shadows through the window. Connect the HDRI to the Color attribute of the Sky Dome light.
Increasing the Diffuse samples reduces noise in the image, however, the render times become more costly and even with 8 Diffuse samples the image is still noisy.