Lighting with the Physical Sky

 

The Physical Sky is a very easy way to get accurate lighting in your scene. Simply by adjusting the 'Elevation' and 'Azimuth' settings it is possible to create an interesting 'golden hour' lighting effect. This can be achieved very simply by going through the following steps.

It is not recommended to use a skydome_light for interior scenes. 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, quad lights or directional lighting would be a better option.

Scene lit with a Physical Sky node connected to a Sky Dome light

 

  • Start off by creating a Physical Sky shader.
  • Create a SkyDomeLight and connect the Physical Sky to the color attribute of the SkyDomeLight.
  • IPR render the scene and adjust the Elevation and Azimuth settings so that the sun is shining through the window and hitting the far right wall and floor. In this case, the Elevation is quite low (15), and the Azimuth has been angled so that the sun light hits the far wall (143). 

Atmosphere Volume

The SkyDome light will not contribute any volume/atmosphere scattering effect. However, we can cheat this by adding a spotlight to the scene

  • Position a spotlight so that it points through the windows. Rotate it so that it matches the angle of sunlight from the Physical Sky. Be aware that we now have two lights representing sunlight in our scene. This will create two types of shadows which we do not want (the spotlight is only being used to create a volume scattering effect). If this effect is apparent, you could try to disable 'enable_sun' in the physical_sky shader and use the spotlight to simulate the direct sunlight.

Spotlight pointed through window

 

To achieve a 'god ray' effect, we can add a Gobo filter to the spot light. 

  • Select the spotlight and connect a Gobo filter to it.
  • Select the gobo and connect a noise map to the Slide Map.
  • Enable Atmosphere Volume and increase the Density to 1.
  • Finally, change the Color Temperature of the spotlight to around 4500 to get a nice warm sun light effect through the windows.

Spotlight with Atmosphere Volume added to scene

 

 

Further example of an interior lit with a Physical Sky connected to a Sky Dome light

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