4. Global illumination with internal lighting,
HDRI, and other methods
The ubiquity of the floating-point pipeline allows for HDR texturing and
global illumination with HDRI maps, as well as the pushing of ranges
using completely internal systems. For example, LightWave 7’s
Radiosity Intensity feature would allow for a setting such as 1000%.
Adding an object to such a blinding environment would normally give
you a render that is flat white (or deceptively speckled). Using exposure
adjustment settings (in this example: white point set to 10.0 and black
point set to 1000%) compresses that information down into a displayable
bit depth, giving you an image very similar to one rendered with 100%
radiosity. As mentioned in the section about curves above, the black
point could then be pushed even higher, adjusting the tonal range of an
image that was previously completely white.
A. Light is light (HDRI or not)
If you were to make an array of lights with the same placement, inten-
sity values, and colors as individual areas of an environment-wrapped
HDRI map, you could conceivably get results similar to radiosity ren-
ders — though the results might not be as convincing without a huge
number of lights. Who has the time for that, and who has the patience to
use as many “lights” as LightWave can generate automatically? You
might be able to accurately represent a simpler environment with a few
well-placed area lights, or you might need to capture all of the subtle col
-
oration, shadow density, and shadow shaping that would be provided by
using an HDRI map captured from a real location. You may even choose
to combine the two. In this respect, each facet of the LightWave system
allows you to choose where to expend your time. You do not have to use
HDRI to take advantage of this data.
B. Mixing it up
I. Using familiar controls — LightWave’s renderer is “full precision” at
its core. Any surface can generate a 1000% luminous glow, for example,
and lighting can range from tremendous subtlety to overpowering
brightness. The resulting render can be adjusted by the same means
mentioned above. Even Skytracer renders skies with FP ranges, so you
can easily use it directly as a “light source” in your radiosity scenes, or
“bake” the sky in an HDR file format so that you don’t have to recalcu
-
late it for every frame.
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LightWave’s “Full Precision” Renderer and You
555
II. Using images only — Thanks to LightWave’s radiosity features, you
can light a scene entirely with images. By surrounding your scene with
an image map, the subtle colors and intensity values contained in the
image map are used to trace light “sources” from their relative locations,
as recorded in the map. This process — a subset of what is referred to
as “global illumination” — is an accurate way to match CG elements
with real environments, and imparts a range of hues and intensities into
your scenes that is difficult to reproduce with internal lighting. These
images can actually be any image that you produce, with any range of
data, including any type of image that LightWave can load. You can use
24-bit images, but the range and precision of the color values will not be
as great.
III. Combining images and internal stuff — LightWave provides the abil
-
ity to “bake” radiosity calculations into image maps. You can choose to
bake everything that you see (other than camera-relative properties like
specularity and reflections) into image maps so that you do not have to
recalculate the radiosity solution. In many cases, you can choose to bake
only your diffuse shading into image maps, then combine the baked
radiosity with rendered lighting to either provide the major lighting for
the scene or augment the shading produced by the baked solution. You
can also choose to use HDRI as the global light source, and place item
lights in order to generate a more specific lighting direction, generate
caustics, or provide different shadows than those which are based
entirely on your maps. The following images show the same scene lit by
different HDRI maps, one of which gets a nudge from a placed light
source:
Images courtesy of Terrence Walker of Studio ArtFX
A. Skull lit with a desert map and a strong
light source to the right.
B. Skull lit entirely with an HDRI map and
radiosity.
IV. Other methods — In addition to the many tools available inside
LightWave, there are a few external options for adapting HDRI maps for
use in LightWave. At the time of writing, there is only one solution for
editing of HDR images, that being HDRShop. There is also a process
Appendix
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