Lighting an Exterior Daylight Scene - Photographic Rendering with V-Ray for SketchUp - page 125

Note
Just in case we are not entirely certain about what is meant by the term occlusion
shadows, here is a brief explanation. In computer graphics, the term ambient oc-
clusion is used to describe the shadowing effect seen on any portion of an ob-
ject's surface that is not visible to the environment (or as it is often called), ambi-
ent lighting found in a scene.
In the following screenshot example, we have one of the tables from our exterior en-
vironment being lit by nothing more than a V-Ray Sky map that has been placed in
the GI (Skylight) slot. Our Skylight is not a direct light, but rather an example of in-
direct environment or ambient lighting. So, the dark area we see beneath the table
isn't being created by any kind of directional shadow but is instead an example of
occlusion shadows at work, albeit in this case fairly weak ones.
Occlusion shadows are often referred to by animators as contact shadows due to
the fact that they clearly show when two objects are either in close proximity to or
actually in direct contact with one another. We see an example of this in the objects
sitting on the table as well as the table and chairs themselves as they sit on the floor
geometry.
Making certain that we are creating occlusion shadows in a scene that looks appro-
priate for the type of environment and lighting conditions that we are using will for a
certainty go a long way towards giving our image believability. Again, this means we
need to pay close attention in the reference gathering and observation phase of our
work so as to discern just how occlusion shadows ought to be working.