process, so each frame of an animation can generate visibly different
results — this is one reason that Monte Carlo is preferred. These set
tings can be fine-tuned for different situations however, so it can be used
to generate faster renders than Monte Carlo, while providing a real
bounce, unlike Backdrop Only.
IV. gMil — Though not radiosity, much less a radiosity mode, gMil
should be mentioned in context with the other global illumination
options available to you. gMil is a shader-based third-party solution (by
Eric Soulvie) for generating global illumination effects. It is an “occlu
sion” shader, which means that it searches for how accessible to lighting
the geometry might be. Its results are similar to the Backdrop Only
radiosity mode, but it has specific controls for determining where the
illumination effects are applied, as well as more options for determining
what is affected. As it is a shader, it can be applied on a per-surface basis,
which can save time when you do not need to generate radiosity for an
entire scene.
Hydrant geometry courtesy of MeniThings
I. Backdrop Only
radiosity - Notice that
there’s no color “bleed
ing” between the
objects in the scene.
II. A Monte Carlo ren
der of the classic “Cor
nell box.” There is no
noise, but the render
time was considerable
when compared with
the Interpolated
III. Interpolated
Radiosity - The settings
used for this scene
cause it to render much
faster than a Monte
Carlo version, but the
splotching has been
retained to show the
IV. gMil - This scene dif
fers from image (I) only
in that gMil was used
for all shading. Notice
that the darks are
darker with default
B. Ambient intensity and radiosity
This comes directly from Arnie Cachelin: “When Radiosity is enabled,
the ambient light value is added only to the indirect diffuse lighting of
surfaces, not to the direct lighting. This means that the ambient level
functions as the sum of all the higher order diffuse light ‘bounces.’ This
little-known solution provides adjustable levels of higher order lighting,
which is generally a very subtle effect, while avoiding the exponential
increase in the number of expensive ray-trace operations otherwise
required by multi-bounce global illumination solutions. Contrary to your

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