Biomedical Engineering Reference
In-Depth Information
material points can be tracked over time and local me-
chanical properties (e.g., strain) can be computed. The
visualization method presented here utilizes the simi-
larity between the B-spline representation of the motion
fields and the graphics hardware support for non-uniform
rational B-spline (NURBS) display with texture mapping
to achieve high-performance visualization of
transformation computations associated with the verti-
ces, while the pixel filling operation for the small tri-
angles would be fast. The opposite is true when the
number of triangles is few but their size is large. Thus, an
optimal balance between the two factors yields a good
overall system performance. Another factor that affects
speed is the geometric technique used in visualization. A
simple technique may execute much faster because of its
use of instruction and memory cache, whereas a more
intelligent and elaborate technique that does not make
effective use of instruction and memory cache will be
slower. Since biomedical images are usually large, effi-
cient use of cache capabilities of
these
parametric fields.
6.6.8 Discussion
6.6.8.1 Speed issues in visualization
systems
the hardware is
essential.
6.6.8.2 Future issues in visualization
Speed issues often become the essential factors that
determine the usefulness of a visualization system. Vi-
sualization involves two types of basic graphic operations:
One is related to the geometry, such as the trans-
formation of the vertices of a polygon, and the other is
associated with displaying pixels. In the graphics
processing pipeline, the overhead can happen in either of
these two operations and adversely affect the speed of
the entire system. Thus, for instance, drawing a large
number of small triangles would cause overhead in the
Many potentially important visualization concepts did
not develop successfully in the past because of the lack of
proper systems. These concepts had memory and pro-
cessor speed requirements that were then considered
unreasonable. This led to the development of logically
more complex systems, which, in turn, created several
other diversions. With processors and memory becoming
more efficient and less expensive, and with the rapid
Figure 6.6-22 Visualization of the displacement field during heart motion. (Left) Triplanar view of a 3D parametric map (top) used
for the 3D texture mapping of a NURBS representation of the displacement field (center) and modulated with image data (bottom).
(Right) Cine-frames of volumetric rendering of the NURBS generated displacement fields during the full cardiac cycle, starting
from end diastole at top left. (Frame order: left-to-right, top-to-bottom.) (Images courtesy of M. Solaiyappan, Cengizhan Ozturk,
Elliot McVeigh, Albert Lardo.)
