Download Multi-Scale Extreme Simplification and Rendering of Point Sets

number of points, so that the threshold can be the same for most models and
AMG scales.
Figure 4.11: If two domains are considered neighbors even when they only share
one point, artifacts may occur.
In figure 4.12 we visually compare the dark back-face method to the overlapping domains method. When using the dark back-face method we see areas
that are too bright, because there are too much fragments in the prefix. This
problem does not occur when using the overlapping domains method. Instead
we see some dark silhouettes, for example around the tail, that do not occur in
the dark back-face method.
Figure 4.12: The bunny model is rendered using the dark back-face method in
a and the overlapping domains method in b. We see areas that are too bright
encircled in a, caused by an incorrect prefix (defined on page 37).
This problem of the overlapping domains method is caused by the fact that
the depth buffer is used to protect pixels from being overwritten. All pixels that
a domain primitive occupies are locked, also the pixels for which the fragment
has a low alpha value, meaning that the influence of the domain primitive is
small. This may result in a black silhouette around domain primitives. This
effect can be diminished by increasing the minimum alpha value for which pixels
are locked, by using an alpha test. In figure 4.13.a the balljoint model is rendered
by using point primitives. In figure 4.13.b the domain primitives are rendered
using the overlapping domains method. A dark silhouette around the ball is
clearly visible. The alpha test reference value is increased to 0.1 in figure 4.13.c,
and the black silhouette is clearly thinner. Of course, the reference value may
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