of silhouette, contour, discontinuity .... silhouette edges in a connected mesh by simply taking the dot product of the transformed view ... in sign between adjacent.
J /,
NASA
Contractor
ICASE
Report
Report
201610
/
/
/ [
/
No. 96-60
ICA EXTRACTING FEATURES FROM 3D UNSTRUCTURED MESHES FOR INTERACTIVE VISUALIZATION
Kwan-Liu
Ma
Victoria
Interrante
NASA Contract No. November 1996 Institute NASA
for
Operated
National Space
Computer
Langley
Hampton,
NASI-19480
VA
Applications
Research
and Engineering
23681-0001
by Universities
Aeronautics
Space
and
Administration
Langley Hampton,
in Science
Center
Research Virginia
Center 23681-0001
Research
Association
Extracting
Features from for Interactive
Kwan-Liu Institute
for Computer
3D Unstructured Visualization
Ma and
Victoria
Applications
Meshes
Interrante
in Science
and
Engineering
Abstract This paper describes techniques, the visualization and interactive
based on the extraction manipulation of the
of geometric features, for facilitating typically very large and dense three-
dimensional unstructured grids used in aerodynamics We discuss the difficulties that scientists currently
calculations. face in efficiently
and
effectively
dis-
playing
geometric
lines
to clearly
and
these
concisely unnecessary
meshes
indicate
We describe discuss
ing these
features
the
the
visual
features,
performance
and
propose
essential
methods
structural
for using detail
of the
model
feature while
eliminating
much
of the
clutter.
the perceptual the
practical
(taking of each
importance implementation
into consideration proposed
technique
of specific
viewpoint-dependent
of simple both
local
on various
but
effective
and global types
and algorithms
criteria),
of data
and
view-independent for identifydemonstrate
sets.
tThis research was supported by the National Aeronautics and Space Administration under NASA contract NASl-19480 while the author was in residence at the Institute for Computer Applications in Science and Engineering (ICASE), NASA Langley Research Center, Hampton, VA 23681-0001.
1
Introduction
The
three-dimensional
generally
very
renderings
large
of many
workstation,
and structure
a typical
rendering
are
skipping
(These
every
nth
By directly features
from
considerably
the
When
time
improve time
with
underlying
2
use
long
history
in this certain They
lines
to stress
show
faces,
but
do not discuss
how
images
resembling
of first calculated scene. narrow
feature
and
they
enhancing
time
on an average
desktop
perceive
1 gives
relevant
an example
of
consisting
of
mesh,
grid containing
4,607,585
techniques
required
for the
gridpoints
of the
of perceptually
that
display
surface
significant
of the
of
mesh,
full model
geometric we may
to all of the above-mentioned of the
presented
it can
data the
simplest
of the standard
in place
concern,
visual
both
methods
data.
be useful
to highlight
to display essential
prominence
for
feature
lines
structural
of the
detail
flow information.
how
standard
[12] demonstrates in the
surfaces
use
of such
and
they
of polygonally
sphere
lines. with
in a complex
model.
Robinson
Saito
objects
can that
sur-
[13] show digital
enable
and
improved
Takahashi
representing how
to a two-dimensional
modeled
overlapping
can
these
[15]
the lines
depth
be used tend,
in
to successfully
two-dimensional
lines
first
and,
and
describe
accessibility
the
a
discontinuity
multiple
from
has
among
be used
Pearson
data
models
operators
tangent
been
representations
low speed
discontinuities,
how
containing
be identified.
of polygonal
gradient
can
can be computed
across
renderings depth
the
have
structure
illustration
models
information
contour,
geometrical
of CAD
line drawings
[4] may
of silhouette,
technical
lines may
of geometrical
Cohen
clarifying from
how such
order
and
importance
lines in images
describe
communication
Dooley
communication
by applying
recesses
the
techniques
shaded
second
Miller
these
preserving
lines
artists'
for visual
and
while
the
grid.) set
compared
of critical
volume
only the
comprehensibility
graphics.
various
these
propose
latency
Figure
some
a coarser
Even
a surface
rendering
a small
displaying
the perceptual
represent
bandwidth
and
the
isoparametric how
photographs
lines.
rendering
of 3D flow are
to adequately
illustrates
the
extracting
to enhance
in computer
cases,
include
resolution.
to compute
2-4 illustrate
to decrease
simulation
Work
of feature
field
picture
or volume-rendered
geometry
and
from an unstructured Figures
is not
surface
Previous
The
mesh
shape
of overlapping
or substituting and
numerical
it can be difficult
This
the rendering
rendering
in conjunction of the
element,
surface
same
tangle
grid.
techniques
decrease
at the
the
points.
identifying
in both
is produced
in practice
for the
can be time-consuming
was extracted
804,056
used
datasets.
and
through
used
irregular
meshes
of a CFD
across
grids
and
an image
that
commonly
such
of these
triangles,
tetrahedra
in size
once
geometric
127,544
unstructured
locus can
map
of the
to identify
on actual
be
the
objects,
_'"
Figure aircraft.
1: A surface
Figure
mesh
for the
2: The
same
numerical
dataset,
simulation
with
only
i
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of airflow
the
gridpoints
._,_._ t
over
_
a low-wing
displayed.
transport
Figure
3: The
same
dataset,
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with only
every
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