Lighting an Exterior Daylight Scene - Photographic Rendering with V-Ray for SketchUp - page 140

Filling in with skylight
Before going ahead and starting work on the skylight, however, this would seem like a
good time for us to go back and consult the lighting definition that we have written for
the scene and see if we can get a sense of what we may want or need our skylight to
do. The problem we have of course is that I didn't really add anything to the definition
that specifically outlined the type of fill or skylight required.
Could we go ahead and do that now even though we are well under way with our
lighting creation? Well the simple answer is yes, we should never feel that it is too late
to improve any of the scene definitions that we create. If we get to a point in our pro-
ject where we realize that our blueprint is missing even a single piece of information,
something we feel would be useful to us, taking the time out to add it in can only be
beneficial in the long run.
We do have a bit of a starting point in that our current definition mentions that we
wanted the occlusion shadows in the scene to be fairly strong. This in and of itself
would seem to suggest that we want a fair amount of illumination to be coming from
the sky. It perhaps naturally follows then that as well as receiving a good level of il-
lumination, our shadowed areas should also be receiving a fair amount of coloration
from sky. At the suggested time of the day, that would mean seeing quite a noticeable
blue tinge in the shadows.
Of course, the big question is which of the skylight options available in V-Ray should
we make use of in order to accomplish our stated goals? Given that we already have
the TexSky map in place, we could for instance simply turn on the indirect illumination
systems and make use of the V-Ray Sky. The problem with this default daylight setup
however, is that the default Irradiance Mapping and Light Cache GI engines aren't in
all honesty tremendously good at producing the kind of strong occlusion shadows we
are looking for. Their strength, as you have already seen, is their ability to bounce light
around interior spaces very quickly while at the same time still producing very natural-
looking lighting solutions even when using low quality GI settings.
Using the V-Ray Sky
This doesn't mean we couldn't make use of the V-Ray Sky if we really wanted to. It
just means that we would need to make better use of the GI engine options available