Graphics Reference
In-Depth Information
Figure 14.18: Left: The water surface heightfield in CryEngine2. Right: Real-time render-
ing of the dynamic heightfield [Mit07]. (Credit: Courtesy of Tiago Sousa, ©Crytek)
sets and use the most efficient interpolation scheme available. This is a particularly
good approach for measured shapes, where the dense point sets naturally arise
from the measurement process.
Point-based modeling often stores points at densities so high that the expected
viewpoint and resolution will yield about one point per pixel, as shown in Fig-
ure 14.19. The interpolation thus need only cover gaps on the order of a pixel.
Splatting
is an efficient interpolation scheme under these conditions: Each point
is rasterized as a small sphere (or disk facing the viewer) so that the space between
points is covered but the overall shape conforms tightly to the point set. This
is simply a form of convolution, and it is also equivalent to an implicit surface
defined by a radial function that rapidly falls to zero (and is therefore trivial to
evaluate). One can thus also directly ray-trace a point set, using the associated
implicit surface.
Because they are a natural fit for measured data but present some efficiency
challenges for animation, modeling, and storage, point representations are cur-
rently more popular in scientific and medical communities than entertainment and
engineering ones.
Objects that have a small screen-space footprint or that are sufficiently distant that
parallax effects are negligible present an opportunity to improve rendering perfor-
(a)
(b)
(c)
Figure 14.19: (a) A point set, with attached surface properties. (b) The gaps between points
when rendered at this resolution. (c) The surface defined by splatting interpolation of the
original points [PZvBG00]. (Credit: courtesy of Hanspeter Pfister, An Wang Professor of
Computer Science, © 2000 ACM, Inc. Reprinted by permission.)
