Autodesk LIGHTSCAPE, Manual

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Radiosity Processing 11
186
Lightscape
In this example, no light beam is visible because the
maximum sample spacing is set too high (larger
than the surface itself) and none of the original
sample points fall within the beam of the light. There
are no original sample points in the light beam, so no
adaptive subdivision is triggered—in a sense, the
light beam “falls between the cracks.”
This demonstrates the significance of the maximum
setting. It is important to select a value that ensures
that at least one initial sample point falls within each
light beam. The default is a good starting point, but
if you find that certain light sources do not seem to
be illuminating the intended surfaces, it may be that
the initial mesh parameter is too large.
Mesh Spacing Example 2: Coarse illumination
Receiver Mesh Sample Spacing
Min: 300 mm; Max: 1000 mm
Subdivision Contrast Threshold: 0.4
In this example, the maximum setting is decreased
but the result looks crude because the minimum
sample spacing is not small enough to sufficiently
capture the shape of the light beam. Notice the adap-
tive subdivision around the light.
Mesh Spacing Example 3: Refined illumination
Receiver Mesh Sample Spacing
Min: 100 mm; Max: 1000 mm
Subdivision Contrast Threshold: 0.4
The result in this example looks much better,
although the number of mesh elements generated is
greater. The mesh is well shaped, the adaptive subdi-
vision is triggered only where desired—near the
light beam.
Mesh Spacing Example 4
Receiver Mesh Sample Spacing
Min: 100 mm; Max: 1000 mm
Subdivision Contrast Threshold: 0.1
The only difference between this example and
Example 3 is that the Subdivision Contrast
Threshold is changed to make it more sensitive to
adaptive subdivision.
The final image looks the same as the one in
Example 3, but the mesh display shows that the
whole surface is unnecessarily subdivided to the
Minimum Sample Spacing. Although the display
results are the same, this example generated a
considerably larger number of mesh elements, most
of which were unnecessary—wasting processing
time and memory.
Example 2: Display Example 2: Mesh
Example 3: Display Example 3: Mesh
Example 4: Display Example 4: Mesh