ab 0, why does the sun illuminate the surfaces in the room (i.e. sun patch), but not the sky, although I can see both through the opening?
This has to do with the way Radiance works with different types of light sources. The sun is modeled as a “source”, which is dealt with by Radiance’s direct lighting calculation. It turns out to be very easy to determine whether or not a surface is directly illuminated by a source, so this is done very quickly. This is done even with -ab 0. The sky is modeled as “glow”, so it will only take part in Radiance’s indirect lighting (i.e. interreflection) calculation, which is only performed for values of -ab greater than zero. This involves the process of generating extra rays at each intersection of a ray with a surface and checking if any of them will hit the “glow” source (or any other source, or an illuminated surface). The higher the value of -ab, the more subsequent reflections will be considered.
Related Questions
- ab 0, why does the sun illuminate the surfaces in the room (i.e. sun patch), but not the sky, although I can see both through the opening?
- Has Sun already started to reap the benefits of opening up this technology to the open-source community?
- How long does it take to paint a Dark Sky Mural in an average size room?
