NAME
ContourNaN
DESCRIPTION
This module generates contour geometry for a 2-D lattice. It can create
the basic contour lines over a particular data range like the Contour
module, but it also adds many other options. ContourNaN provides
tube contours as well as real filled contour bands with optional face or
vertex normals. ContourNaN can remove special values by the grid
point or by the whole lattice cell. ContourNaN also includes all the
options found in NCSA's Contour2 module. These include optionally
showing the zero contour, dimming the colors of negative contours,
setting the contour range to be data dependent or fixed, and specifying
the contours by a number of levels or an exact interval. A final
significant feature is the ability to create unevenly spaced contours
with a configuration string (typically from the ColorBands module).
INPUTS
Input -- Lattice
(2-D, 1-vector, float, perimeter..curvilinear).
This is the lattice used for contouring.
Transform -- Lattice (Opt.)
(2-D, 1-vector, float).
This is an optional 4x4 transformation matrix (typically from
TransformGen) that allows rotation and translation operations to be
applied to the resulting geometry.
Colormap -- Lattice (Opt.)
(1-D, 4-vector, float, uniform).
This is an optional lattice used to color the contour values.
Configuration In -- Parameter (Opt.)
This is an optional configuration string (typically created by the
ColorBands module) that can be used to create unevenly spaced
contours with particular colors. If valid configuration data is present
then it will override and disable the settings of the widgets that deal
with specifying the contour values ("Range Type", "Contour Method",
"Range Start", "Range End", "# Levels", and "Interval"). It will also
override any connected colormap lattice.
WIDGETS
Contour Type -- Option Menu
This determines the style used to draw the contours.
Filled - Draws solid bands between the contour levels. The color of
a band is determined from the middle data value between the levels.
Line - Draws regular line contours.
Tube - Draws line contours but using tubes instead of plain line
segments.
Capped Tube - Draws the contours as tubes with spheres at the ends
of the tubes in order to give them a smoother appearance.
Dimension -- Radio Box
This selects how the contour geometry is to be drawn based on the
setting of "Contour Type". It can be represented as points, lines, or
shaded polygons. Lowering the dimension will speed up rendering for
better interactive manipulation. However, it will not increase the
dimension beyond what "Contour Type" specifies.
Use Normals? -- Option Menu
This selects whether normals will be added to the geometry. The
default is no normals, but if the geometry looks oddly colored (i.e.
containing erroneous dark patches) in Render then using this option
will fix the problem at the expense of some extra memory and
processing time. Normals can be applied on a per-face or per-vertex
basis. Using face normals may result in the geometry having a faceted
appearance since for each triangle the lighting is the same at all of
its vertices (and consequently over the entire triangle). Using vertex
normals allows each of the vertices of a triangle to have different
lighting resulting in smooth shading between triangles that share
vertices. There is no difference between using face normals or vertex
normals when the geometry is completely flat.
Line Width -- Slider
This sets the width of the contours when they are drawn as line
segments by either setting the "Contour Type" to "Line" or setting the
"Dimension" to "1-D".
Tube Scale -- Dial
This is the scaling factor to be applied to the radius of the tube and
capped tube contours.
Complexity -- Slider
This is the complexity to be applied to the geometry when contours are
drawn as tubes or capped tubes. The larger the complexity, the more
polygons are used to create these objects. The range is from 0.0 to 1.0.
A value of .5 generates about 200 polygons for a sphere. Larger
complexity values can SIGNIFICANTLY reduce rendering speed when
there are many objects.
Range Type -- Option Menu
This determines how the contour range specified by the "Range Start"
and "Range End" widgets is used. It can be data dependent (the
default), whereby the starting and ending range values are always set to
the minimum and maximum data values of the input lattice. The range
can also be fixed so that any starting and ending value is possible.
Range Start -- Dial
This is the lower bound of the contour range.
Range End -- Dial
This is the upper bound of the contour range.
Special Value -- Text
This is data value that should be treated as "special" according to the
setting of the "Special Value Type" widget.
Special Value Type -- Radio Box
This determines how special values will be treated. The default is to
keep them and include them as part of the geometry. Special values
can also be removed by eliminating their grid points or the entire
lattice cells that they are a part of. Choosing "Remove special value
grid points" results in a smoother appearance since it tries to preserve
as much of the lattice cells as possible while removing the points
without interpolating around them. Choosing "Remove special value
cells" not only removes the special value grid points, but also all
adjacent ones resulting in a course appearance that reveals the size of
the lattice cells in the grid.
Contour Method -- Option Menu
This determines how the contour values are chosen. If "# Levels" is
selected (the default) then the specified number of levels will be
generated over the the entire contour range using an appropriate
increment. If "Interval" is selected then the specified value will be
used to increment from the "Range Start" to the "Range End". Both
methods will create evenly spaced contours. The "Configuration In"
port in conjunction with the ColorBands module can be used to create
unevenly spaced contours.
# Levels -- Slider
This is the number of evenly space contour levels covering the entire
contour range. It is directly used when the "Contour Method" is set to
"# Levels".
Interval -- Dial
This is the data increment for calculating evenly spaced contour levels
beginning at the "Range Start" value. It is directly used when the
"Contour Method" is set to "Interval". The interval does not have to
divide evenly into the contour range; it will just fall short of the
"Range End" if it doesn't.
Show Zero Contour? -- Option Menu
This determines whether contours with a value of 0 are shown.
Dim Negatives? -- Option Menu
Setting this option draws negative contours with 50% intensity of
their original color.
Lighting Model -- Option Menu
This is the method used to light all the contour geometry. The default
is Phong lighting, but flat lighting can also be set, which is especially
useful for flat planes of filled contours so that they will be colored
exactly as specified and not modified by the scene's lighting. The
lighting model is meaningless for plain pixel-width line contours.
OUTPUTS
Output -- Geometry
This is the contour geometry.
Configuration Out -- Parameter
This is a string containing information about the contour levels and
colors created by ContourNaN when the "Contour Type" is set to
"Filled". It can be connected to the "Configuration In" port of the
ColorBands module in order to generate a color key that is actually
representative of ContourNaN's geometry in the filled case. It is only
necessary with filled contours since they use the middle value between
two contour levels for coloring rather than the values at the contour
levels.
KNOWN PROBLEMS
ContourNaN is a good deal slower than the Contour module when there
are many contour levels or when the input lattice is reasonably large.
Hopefully, the next version will be faster. Also, the geometry could
probably be optimized further to reduce its size. There are no known
bugs.
SEE ALSO
ColorBands, Contour, Contour2, LatToGeomNaN
-
Hans Vahlenkamp (Hans.Vahlenkamp@noaa.gov)
Geophysical Fluid Dynamics Laboratory / NOAA
Princeton University Forrestal Campus
http://www.gfdl.noaa.gov
