Indirect lighting of interior scenes can be a challenge, but there are some things you can do. In this post, we’ll give you some quick tips, but you can find more detailed information on support.solidangle.com, both for interior lighting and for troubleshooting noise.
Avoid the Skydome and use a Sky background and Quad lights
Instead of using a Skydome light, use a Sky for the background and quad lights for the light coming in through the windows. The quad lights should just barely cover the entire window.
If there’s anything visible outside the window, you may want to put a spot light on them. Just be careful not to let the spot light go into the room.
Use a distant light to simulate beams of light coming into the room
A distant_light is an easy-to-use option that perfectly matches sun light.
Spot lights don’t produce realistic sun beams since the beams look like they’re expanding, which sun beams don’t do. Moving the spot light further back, and also making sure it’s no larger than it needs to be to illuminate the window, will reduce noise and make it look more realistic.
Don’t put lights too close to the windows
If a light is too close to the window, that means the light hitting the window area is significantly more concentrated and so much brighter than the light hitting the far side of the room and so this produces more noticeable noise.
Make sure your materials are physically based
For example, don’t shade the room Standard shaders with a Diffuse weight of 1, and Diffuse color full white (1 1 1). I don’t think there’s any material known to man that is this reflective. Lowering the Diffuse weight to 0.7 will roughly match white paint and it will also get rid of noise. If it’s too dark, then try increasing the intensity of the lights, increase the number of diffuse bounces, or increase the camera’s exposure.
For a richer look, avoid fake lights inside the room
Consider getting rid of any fake lights you may have inside the room, and instead increase the number of diffuse and glossy bounces in order to get an even more realistic look, not to mention make the lighting easier. Doing that does increase render times, unfortunately, but does give a richer look.
hat tip: Thiago