line probe - sample a 3D field along a line
Name
line probe - sample a 3D field along a line
Summary
Name line probe
Type mapper
Inputs field, 3D, any-data, any-coordinates
field, any-data, any-coordinates (optional)
colormap (optional)
upstream geom (optional, invisible)
Outputs field, float, irregular
geometry
Parameters
Name Type Default Min Max Choices
probe mode radio manual manual, mouse,
sample file,
sample field
all samples toggle off -
probe x float 0.0 unbounded
probe y float 0.0 unbounded
node size float 0.0 0.0, unbounded
probe values text_block - -
sample file browser $NULL -
sample choices browser $NULL -
Description
The line probe module can be used to sample a 3D field along one or
more lines or paths. The location of the probe may be entered manually,
indicated by pointing and clicking the mouse, selected from a file of
sampling locations, or determined by the sampling locations in a second
field. If either of the sampling options is used, one sampling location
may be selected, creating one probe, or all sampling locations may be
selected, creating multiple probes, one for each sampling location.
Except for the sample field mode, the probe will be a vertical line
running through the height of the data volume at a constant X and Y
position. By using the sample field mode, the paths of the probes may
be non-linear, like trajectories.
If the line probe module has created a single probe, the values found at
its intersections with each of the fields layers will be listed in a
text browser and output as a 1D field. If multiple probes are created,
the output field is 2D (one "row" for each probe) but the values are not
shown in the text browser. In either case, a polyline geometry object
is created for the line probe(s) and spheres may be used to show the
locations of the nodes (sampling points along the probe). If an
optional colormap is provided and the field consists of scalars, the
line probe and its nodes will be colored based on how the values along
the probe map into this colormap. If a colormap is not provided or the
contains vectors, the line probe and its nodes will not be colored.
Inputs
Input Field (required, field, 3D, any-data, any-coordinates)
The input data must be a 3D field of scalar or vector values in
3D space. Any data type in any grid configuration may be used.
Input Sample Field (optional, field, any-data, any-coordinates)
The optional sample field (computationally 1D, 2D, or 3D) may be
used to define the sampling locations of the line probe module.
Only the positions of the sample field's data points are used -- the
the data values are ignored. Each computational "row of the sample
field defines the path of a single probe. Consequently, a single
line probe module can be used to create any number of probes, each
probe following a predefined path which need not be linear -- like
trajectory. This sample field will be used only if the probe mode
is set to sample field. If the all samples toggle is off, only the
first probe path will be used. If the all samples toggle is on, all
of the paths defined by the sample field will be used, each path
defining a single probe.
Input Colormap (optional)
If the input data are scalars and an optional colormap is supplied,
the line probe geometry object will be colored according to the
data values found along the probe and how these values map into this
colormap.
Input Upstream Geom (optional, invisible, upstream geom)
To allow operation of the line probe in mouse mode, the Input
Upstream Geom port must receive upstream geometry data from the
the render geometry module. Among other things, this data contains
the location of the point clicked on by the mouse. AVS makes this
connection automatically when the line probe module is instantiated.
Parameters
probe mode
The probe mode parameter is used to select the method by which the
user intends to position the line probe. In manual mode, the user
enters the desired position through the probe x and probe y param-
eters. Mouse mode allows the user to position the probe by pointing
the mouse cursor at the desired point and then clicking. Sample
file mode allows the user to select a location from the list of
sample locations in the sample file (q.v.). If the all samples
toggle is off, only the one sample location will be used. If the
all samples toggle is on, all of the sample locations in the file
will be used, creating one probe for each location. If the sample
field mode is selected, the locations of the data points of the
input sample field will become the line probe sampling locations.
If the all samples toggle is off, only the first computational "row"
will be used, creating only one probe. If the all samples toggle is
on, all of the sample fields "rows" will be used, creating one probe
for each "row". In all modes but the sample field mode, the line
probes will be vertical (orthogonal to the computational "K" layers
of the data field). The sample field may be used to define probes
that are neither linear nor vertical.
probe x
probe y
These parameters are used to indicate the horizontal position of
the probe. In manual mode, the user types in the desired location
through these parameters. In all other modes, these parameters are
updated with the current location of the probe. When one of the
sample modes is used and all samples is on, the probe x and probe y
parameters are meaningless and are shown as zeroes. In sample field
mode, since a probe may define a non-linear, non-vertical, these
parameters will reflect the horizontal location of the first point
only.
node size
The node size parameter controls the radius of the spheres created
at each of the points along the line probe. A node size value of
0.0 disables this feature.
probe values
The probe values parameter is an output-only text browser and lists
the values along the probe. If multiple probes are created (one of
the sample modes has been selected and all samples is on) the probe
values will not be shown and the text browser will be blank.
sample file
sample choices
If the sample file mode has been selected, the file specified as the
sample file is read and its contents are displayed as the sample
choices. If the all samples toggle is off, the user may then select
one of the sample choices and a single probe is positioned at the
selected location. If the all samples toggle is on, all of the
choices will be used and a probe will be created at each of their
locations.
The sample file is an ASCII file, each record (line) of which
contains an X and Y coordinate pair, indicating the position of a
sample point. The X and Y values should be separated by white
space. The X value may be preceded by an optional non-numerical
label that may be used to identify the sample point to the user.
Outputs
Output Field (float, irregular)
The values found along the line probe are output as a 1D field if
a single probe has been created. If multiple probes have been
created, the output will be a 2D field, with one "row" of the field
for each probe. The grid configuration is always irregular and the
data type is always float, regardless of the grid configuration and
data type of the input field. The vector length of the output field
is the same as that of the input field.
Output Geometry
A geometry object that contains one polyline for each of the probes
is created. Its name is "line_probe". If the node size is greater
than 0.0, a second object containing spheres at each point along
the probe(s) is also created. This second object is named "line_-
probe_nodes" and is a child of "line_probe". Both of these objects
will be colored if the optional colormap is provided.
Example
This first example uses a single line probe to sample a 3D field through
a point identified on a slice of the field.
READ FIELD
|
|
|
| GENERATE COLORMAP
| |
+--------------------+
| | |
ORTHOGONAL SLICER | |
| LINE PROBE
FIELD TO MESH |
| |
+--------------------+
|
RENDER GEOMETRY
|
DISPLAY PIXMAP
This second example is similar to the first except that it uses a
second line probe in a second 3D field, collocated with the first,
to control the position of the first probe. In this way, two fields
may easily be probed at the same locations.
READ FIELD READ FIELD
| |
| |
| GENERATE COLORMAP LINE PROBE
| | |
+------------------------+ |
| | +-- | ---------+
| | | |
ORTHOGONAL SLICER | | |
| LINE PROBE
FIELD TO MESH |
| |
+------------------------+
|
RENDER GEOMETRY
|
DISPLAY PIXMAP
Limitations
The presence of spheres as the probe nodes may cause the render geometry
module some difficulty rendering polyline or label objects. If either
of these types of objects are to be used in a scene, it may be best to
disable the probe nodes by using a node size of zero.
This module has been used with uniform and "nice" irregular fields.
It has not been tested with anything really weird.
Author
Phil McDonald, NOAA/ERL/Forecast Systems Laboratory
NOAA/ERL/Forecast Systems Laboratory
AVS Modules line probe