StreamlinePlot (st) Resources

stArrowLengthF

This resource specifies, in units of NDC, the length of the lines used to draw the directional arrows that appear periodically along the length of the streamlines. At initialization or any time stArrowLengthF is given a value less than or equal to 0.0, StreamlinePlot calculates a value for stArrowLengthF based on the NDC size of an individual grid cell assuming a linear transformation from data to NDC space. Otherwise, when stArrowLengthF is not set explicitly, StreamlinePlot makes proportional adjustments to its value in response to changes in the assumed NDC size of the grid cell (resulting from changes to the viewport size and/or the number of elements in the data grid).

Default: <dynamic>

Default: 0.0

stArrowStride

StreamlinePlot draws directional arrows based on the data grid location. No more than one directional arrow can be drawn within each grid box. This resource allows you to draw fewer directional arrows by skipping grid boxes. If stArrowStride is set to 3, for instance, only every third grid box (along each axis direction) will be eligible for a directional arrow. Of course, the arrow will appear only if a streamline is actually drawn within the area of the grid box.

Default: 2

stCrossoverCheckCount

This resource specifies the number of iterations through the streamline-building loop between checks for streamline crossover, that is, one streamline growing closer than stMinLineSpacingF to previously created streamlines. A negative value causes Streamlines to check for crossover only when a new data grid box is entered. At each crossover check, the current streamline position is compared with a sampling of previous streamline positions retained in an internal circular list. This list is currently fixed to a length of 750. Since up to this number of comparisons are performed at each crossover check, the frequency with which these checks are performed can have a noticeable impact on the drawing time.

Default: -1

stExplicitLabelBarLabelsOn

This boolean resource allows you control the labels that appear in the StreamlinePlot LabelBar explicitly. When set True, StreamlinePlot does not block the LabelBar resources lbLabelStrings and lbLabelAlignment. Therefore you can directly control both the contents of the LabelBar's label strings and their alignment with respect to the label boxes. When stExplicitLabelBarLabelsOn is set False, StreamlinePlot sets both of these resources based on the values of the stLevels array resource and the value of the resource stLabelBarEndLabelsOn. If you set this resource True but do not set the lbLabelStrings array resource, StreamlinePlot will set it for you one time. This allows you to get an initial set of strings as a starting point for any customization you want to perform.

Default: False

stLabelBarEndLabelsOn

When this boolean resource is set True and stExplicitLabelBarLabelsOn is False, StreamlinePlot creates labels for the two ends of the LabelBar. The label at one end will be a string representation of a minimum value and at the other end will be a string representation of the maximum value. These values represent either a vector magnitude or, if stUseScalarArray is set True, some other scalar value. Both strings will be formatted according to the format specification in effect for the other labels provided by StreamlinePlot to the LabelBar.

Default: False

stLabelFormat

The stLabelFormat resource is a string that specifies a printing format for StreamlinePlot labels according to the HLU Floating Point Format Specification scheme. Currently, this resource controls the formatting of numerical values supplied to the StreamlinePlot object's optional LabelBar.

stLengthCheckCount

This resource specifies the number of iterations through the streamline-building loop between each check of the streamline growth. If the distance between the current position of the streamline and the position saved at the time of the previous check is less than a minimum amount, defined as stMinStepFactorF times stStepSizeF, then the current streamline is terminated and a new one begun if possible.

Default: 35

stLevelColors

The elements of this array of type NhlTColorIndexGenArray can be set using an array of color indexes, an array of named colors, or an array of RGB or RGBA values.

If stMonoLineColor is False, this resource controls the progressive step-wise coloring of the streamlines based on the interpolated magnitude or other scalar value at each step location.

Each element of stLevelColors specifies the color for locations along the streamline whose associated scalar data value is less than the corresponding element of the stLevels array. Note that there is always one more color than there are levels. The first element of stLevelColors specifies a color index for any location associated data value less than the value of stMinLevelValF. The highest currently used element of stLevelColors specifies a color for locations with associated data values greater than the value of stMaxLevelValF.

Although backwards compatibility is for the most part maintained, beginning with version 6.1.0, this resource supports the new 32-bit color model, as follows:

If stLevelColors is not set explicitly, its values are derived from the settings of stLevelPalette and stSpanLevelPalette, or, if stLevelPalette is not set, wkColorMap and stSpanLevelPalette. If stSpanLevelPalette is True, the values are distributed evenly through the range of colors available from stLevelPalette or wkColorMap. Otherwise, the values are sequential. If the colors are derived from stLevelPalette the first color comes from element 0, whereas if they are derived from wkColorMap, the first color comes from element 2. This is because wkColorMap contains special elements (0 and 1) for the Background and Foreground colors, whereas the palette-type resources do not. If some but not all of the available elements of stLevelColors are explicitly set, the remaining elements will be determined as if stSpanLevelPalette has the value False.

For backwards compatibility, colors set based on wkColorMap remain indexed to the current color map associated with the workstation. Consequently, if the workstation color map is changed prior to drawing the plot, the color indexes will map into the new color map. In contrast, color indexes derived from the stLevelPalette resource always refer to a specific color regardless of changes to wkColorMap.

Default: <dynamic>

stLevelCount

A read-only resource set to the actual number of levels chosen during the level selection process.

Default: 16

stLevelPalette

Available in version 6.1.0 and later.

This resource of type NhlTColorDefinitionGenArray allows you to set a color palette from which the values assigned to stLevelColors are chosen.

You can set this resource to the string name of a predefined color map, an array of named colors, or an array of RGB or RGBA values. If you set stLevelPalette using a predefined color map, it will have two fewer elements than if you set wkColorMap using the same color map. This is because the wkColorMap resource contains special elements (0 and 1) for the Background and Foreground colors, whereas the palette-type resources do not. Use stSpanLevelPalette to indicate whether to span the full color palette or to simply use sequentially increasing values.

Default: None

stLevelSelectionMode

This enumerated resource of type NhlTLevelSelectionMode provides four methods for selecting the levels used to color the streamlines:

AutomaticLevels

Ordinarily this mode determines levels by picking a spacing value from a set of relatively "round" numbers scaled by powers of 10 to the range of the data. This set of numbers is as follows: 1.0, 2.0, 2.5, 4.0, 5.0. The number of levels chosen will be as close as possible to the value of stMaxLevelCount without exceeding it. Once the spacing is chosen, the minimum level is set to the value of the least multiple of the spacing greater than the minimum data value. Likewise the maximum vector level becomes the greatest multiple of the spacing less than the maximum data value. Based on these values, StreamlinePlot sets the resources stLevelSpacingF, stMinLevelValF, and stMaxLevelValF appropriately.

On the other hand, if you explicitly set the resource stLevelSpacingF to a valid value greater than 0.0 and less than the range of the data, it will be used as the interval spacing. The minimum and maximum levels are calculated as before. If as a consequence, stMaxLevelCount is less than the number of levels so specified, it will be set to the number of levels actually needed. However, if the choice of spacing causes the absolute maximum number of levels (currently 255) to be exceeded, StreamlinePlot will issue a warning message and recalculate the spacing as previously described.

In any case, StreamlinePlot sets the elements of the array resource stLevels to the values of the levels chosen and the read-only resource stLevelCount to the number of levels.

ManualLevels

ManualLevels mode bases the choice of levels on the values of the resources stLevelSpacingF, stMinLevelValF, and stMaxLevelValF. Starting at stMinLevelValF, vector levels are created at intervals spaced by the value of stLevelSpacingF until stMaxLevelValF is reached. The final vector level will always be stMaxLevelValF. StreamlinePlot sets elements of the array resource stLevels to the values of each vector level chosen and the read-only resource stLevelCount to the number of levels. If the current value of stMaxLevelCount is less than stLevelCount, it is reset to the value of stLevelCount. However, if the level count would exceed the absolute maximum number of levels, currently 255, StreamlinePlot issues a warning and chooses a new value of stLevelSpacingF based on the value of stMaxLevelCount.

If you choose ManualLevels selection mode when the StreamlinePlot object is created, and do not set stMinLevelValF, StreamlinePlot will choose levels as if you had set AutomaticLevels mode. If you set stMinLevelValF only, a default spacing is used, and the value of stMaxLevelValF is determined as it would be for AutomaticLevels mode.

ExplicitLevels

This mode allows you to specify the value of each level by explicitly setting the contents of the stLevels array. If you choose ExplicitLevels selection mode when creating a StreamlinePlot object, but do not specify the contents of the stLevels array, StreamlinePlot will choose levels as if you had specified AutomaticLevels mode. Thereafter, when you set ExplicitLevels mode, StreamlinePlot uses the current contents of stLevels, whether or not you set it explicitly.

If the number of elements in stLevels exceeds the absolute maximum number of levels (currently 255), StreamlinePlot issues a warning and the mode defaults to AutomaticLevels. Note that StreamlinePlot always sorts the elements of stLevels into a monotonically increasing sequence. After sorting, stMinLevelValF is set equal to the value of first element of stLevels, and stMaxLevelValF is set to the value of the last element. stLevelSpacingF is set to the average value of the spacing separating each level.

EqualSpacedLevels

For this mode, StreamlinePlot divides the range spanning the dataset minimum and maximum values into stMaxLevelCount+1 equally spaced intervals. stLevelSpacingF is set to the value of this interval. stMinLevelValF is set to the value of the dataset minimum plus the value of stLevelSpacingF. stMaxLevelValF is set to the value of the dataset maximum minus the value of stLevelSpacingF. This results in stMaxLevelCount levels; therefore StreamlinePlot sets the read-only resource stLevelCount equal to stMaxLevelCount.

Default: AutomaticLevels

stLevelSpacingF

When the stLevelSelectionMode is ManualLevels or when the stLevelSelectionMode is AutomaticLevels, and stLevelSpacingF is explicitly set, stLevelSpacingF determines the spacing between vector intervals. Otherwise, the StreamlinePlot object sets the value of stLevelSpacingF based on the levels actually chosen. When the stLevelSelectionMode is ExplicitLevels, stLevelSpacingF will be set to the arithmetic average of the spacing between levels.

Default: 5.0

stLevels

An array of floats containing values that determine the color of incremental steps along each streamline when stMonoLineColor is set False. If stScalarFieldData is valid and the resource stUseScalarArray is set True, the level values are based on the scalar array data; otherwise the level values are based on the magnitudes of the vector elements in the vector field. If the stLevelSelectionMode is ExplicitLevels, you may set these values yourself. Otherwise, the StreamlinePlot object sets the elements of this array.

Default: <dynamic>

stLineColor

This resource of type NhlTColorIndex sets the color index used to draw the streamlines.

Default: Foreground

stLineOpacityF

Available in version 6.1.0 and later.

Sets the opacity of streamlines in a plot. Specify a floating-point value in the range from 0.0 (completely transparent) to 1.0 (fully opaque).

Default: 1.0

stLineStartStride

StreamlinePlot can start only one streamline within each data grid box. This resource allows you to define a sparser streamline plot by allowing only certain grid boxes to be eligible for starting a streamline. If stLineStartStride is set to 3, for instance, only every third grid box (along each axis direction) will be eligible for starting a streamline. A streamline will actually be started within an eligible grid box only if no previously drawn streamline passes through the grid box.

This resource is ignored if the resource stMinDistanceF is set to a positive non-zero value.

Default: 2

stLineThicknessF

This resource sets the thickness of the lines used to draw the streamlines and also the directional arrows. The value acts as a multiplier of a (device-dependent) unit thickness.

Default: 1.0

stMapDirection

This resource controls whether the streamline direction is mapped into the same coordinate space as the location of the vector data grid point, or whether it is rendered in a locally uniform Cartesian coordinate space. This resource has an effect whenever a non-uniform transformation is in effect. These include most of the MapTransformation transformations and IrregularTransformation transformations. Also included are logarithmic transformations provided by the LogLinTransformation and even linear transformations when the X and Y unit size is different.

Default: True

stMaxLevelCount

When the stLevelSelectionMode is AutomaticLevels and stLevelSpacingF is not explicitly set, StreamlinePlot picks a number of levels less than or equal to the current value of stMaxLevelCount. If the stLevelSelectionMode is EqualSpacedLevels, StreamlinePlot picks exactly stMaxLevelCount levels. If stMaxLevelCount exceeds the absolute maximum level count allowed by StreamlinePlot (currently 255), a warning is issued and the value is reset to this maximum. If stLevelSelectionMode is ManualLevels or ExplicitLevels or AutomaticLevels with stLevelSpacingF explicitly set, StreamlinePlot sets stMaxLevelCount to the number of levels actually used if this number is greater than the current value of stMaxLevelCount.

Default: 16

stMaxLevelValF

When the stLevelSelectionMode is ManualLevels, the value of stMaxLevelValF, if set, determines the highest level. Otherwise, StreamlinePlot sets the stMaxLevelValF to a value equal to the highest level chosen by the level setting algorithm.

Default: <dynamic>

stMinArrowSpacingF

This resource specifies an NDC minimum distance for adjacent directional arrowheads along a single streamline. If the data grid is transformed in such a way that adjacent grid cells become very close in NDC space, as for instance in many map projections near the poles, you can use this resource to help reduce the otherwise cluttered appearance of these regions of the plot. If stMinArrowSpacingF is less than or equal to 0.0, then no arrowheads are eliminated. When stMinArrowSpacingF is not set explcitly, StreamlinePlot adjusts its value in proportion to changes to vpWidthF.

stMinDistanceF

This resource specifies a minimum distance in NDC space that is to separate the grid boxes eligible for starting streamlines. Potential starting grid boxes are eliminated until no grid boxes remain that are closer than the specified value in NDC space to any neighboring grid box.

This resource should be considered an alternative to stLineStartStride especially applicable to situations involving non-linear transformations from grid space to NDC space. If stMinDistanceF has a positive non-zero value the stLineStartStride resource is ignored.

When this resource has its default value, 0.0, no starting grid boxes are eliminated.

Default: 0.0

stMinLevelValF

When the stLevelSelectionMode is ManualLevels, the value of stMinLevelValF, if set, determines the lowest level value. Otherwise, StreamlinePlot sets the stMinLevelValF to a value equal to the lowest level chosen by the level setting algorithm.

Default: <dynamic>

stMinLineSpacingF

This resource specifies the minimum distance in NDC that a streamline in progress is allowed to approach existing streamlines before being terminated. In general, giving this value a larger number increases the distance between streamlines, and has a tendency to create more, but shorter streamlines. The spacing is only checked at intervals, so streamlines can sometimes approach closer than the specified distance. The stCrossoverCheckCount resource determines the frequency with with the check is performed. At initialization or any time stMinLineSpacingF is given a value less than or equal to 0.0, StreamlinePlot calculates a value for stMinLineSpacingF based on the NDC size of an individual grid cell assuming a linear transformation from data to NDC space. Otherwise, when stMinLineSpacingF is not set explicitly, StreamlinePlot makes proportional adjustments to its value in response to changes in the assumed NDC size of the grid cell (resulting from changes to the viewport size and/or the number of elements in the data grid).

Default: <dynamic>

stMinStepFactorF

This resource specifies a multiplying factor for the stStepSizeF resource that determines the minimum amount the streamline must have grown each time the stream progress is checked in order not to be terminated. The stream progress is checked each stLengthCheckCount iterations through the stream-building loop. Points of convergence or divergence typically cause stream growth to diminish and the streamline eventually to be terminated.

Default: 2.0

stMonoLineColor

When this resource is set True, streamlines are colored using a single HLU color index, as specified by the value of the scalar resource stLineColor. When False, the elements of the array resource stLevelColors are used to set the colors of each step along the streamline based on the interpolated value of the magnitude or associated scalar quantity.

Default: True

stNoDataLabelOn

This boolean resource, when set True, causes a label to appear when StreamlinePlot is drawn without any data having been provided. Except for the label string, all attributes of this label, including its position, are set using resources belonging to the zero field label. When set False, no such label appears.

Default: True

stNoDataLabelString

This resource contains the string that appears in the 'No Data' label if you draw a StreamlinePlot object without providing any data. No substitution substrings are allowed in this label, since all the substitutions depend on data being available. Except for the boolean switch that turns it on and off, all attributes of this label, including its position, are set using resources belonging to the zero field label.

Default: "NO STREAMLINE DATA"

stScalarFieldData

Specifies the id of a ScalarField data object. If this resource is set with a valid ScalarField object and the resource stUseScalarArray is set True, StreamlinePlot will use the scalar array data for coloring the streamlines. In order for StreamlinePlot to consider the ScalarField object valid, it must find that it has the same number of elements along each dimension as are found in the VectorField object.

Note that currently the number of elements is checked only after strides and subsetting are applied. The data coordinate extents set for the ScalarField object are ignored. For now, the data coordinate extents of the processed ScalarField data are assumed to coincide with the data coordinate extents of the VectorField data.

Default: none

stScalarMissingValColor

When stUseScalarArray is True, this resource sets the HLU index of the fill or line color used to draw portions of a streamline where an interpolated scalar value cannot be determined because of missing data in the scalar field.

Default: Foreground

stSpanLevelPalette

Available in version 6.1.0 and later.

If set to True, and if stLevelColors is not set using explicit values, then StreamlinePlot automatically spans the stLevelPalette resource to determine color index values for stLevelColors. If stLevelPalette is not set then the wkColorMap resource is spanned instead. If set to False, then StreamlinePlot uses consecutively ascending values to populate stLevelColors.

If the colors are derived from stLevelPalette the first color will be determined from element 0, whereas if they are derived from wkColorMap, the first color will come from element 2. This is because wkColorMap contains special elements (0 and 1) for the Background and Foreground colors, whereas the palette-type resources do not.

Default: True

stStepSizeF

This resource specifies, in NDC, the basic step size used to build the streamlines. Where the flow direction changes rapidly, the step size is scaled down from the basic step size in order to retain accuracy. Smaller step sizes produce a more accurate plot at the cost of a longer drawing time. At initialization or any time stStepSizeF is given a value less than or equal to 0.0, StreamlinePlot calculates a value for stStepSizeF based on the NDC size of an individual grid cell assuming a linear transformation from data to NDC space. Otherwise, when stStepSizeF is not set explicitly, StreamlinePlot makes proportional adjustments to its value in response to changes in the assumed NDC size of the grid cell (resulting from changes to the viewport size and/or the number of elements in the data grid).

Default: <dynamic>

stStreamlineDrawOrder

This resource of type NhlTDrawOrder determines when the streamlines are drawn relative to the drawing of other elements of a composite plot. There are three choices:

PreDraw

Draw the streamlines before the standard draw phase; the arrows will be overlaid by any subsequently drawn elements.

Draw

Draw the streamlines during the standard draw phase; the arrows will overlay any elements drawn during the predraw phase, but will underlie elements drawn during the postdraw phase.

PostDraw

Draw the streamlines after the standard draw; the arrows will overlay any elements drawn during the predraw and draw phases.

Default: Draw

stUseScalarArray

If this boolean resource is set True, the resource stScalarFieldData is set with a valid ScalarField object, and the appropriate StreamlinePlot resources are set to enable multi-colored streamlines, then the ScalarField data are used to select the level (and hence the color index) assigned to each glyph. Otherwise, when multi-colored streamlines are enabled, coloring will be based on the interpolated vector magnitude at each step location along the streamline.

Default: False

stVectorFieldData

Specifies the id of a VectorField data object. There is no default for this resource; it is the only resource that must be set in order for the StreamlinePlot object to draw a plot. You may create a StreamlinePlot object without setting the stVectorFieldData resource, and auxiliary annotations such as tick marks and titles may appear as the result of a draw, but the StreamlinePlot itself will not show up. The VectorField object can provide either regularly spaced or irregular rectangular gridded data to the StreamlinePlot object, and the VectorField object provides a number of resources for controlling the ingestion of the raw data.

Default: <none>

stZeroFLabelAngleF

This resource specifies the angle, in degrees, of the zero field label text and its surrounding box.

Default: 0.0

stZeroFLabelBackgroundColor

This resource sets the background color used to fill the box surrounding the zero field label. If you do not want the box to be filled at all, set stZeroFLabelBackgroundColor to Transparent (-1).

Default: Background

stZeroFLabelConstantSpacingF

Normally when stZeroFLabelFontQuality is set to High, the StreamlinePlot object writes zero field label text with proportional spacing. Setting the stZeroFLabelConstantSpacingF to a value greater than 0.0 overrides this behavior. Instead, the distance from the start of one character to the next is computed by multiplying a single standard character width by the value of stZeroFLabelConstantSpacingF. When stZeroFLabelConstantSpacingF has a value between 0.0 and 1.0, characters will overlap. A value of 1.0 implies, on average, no space between characters, while values increasing from 1.0 cause the space between characters to grow. This parameter is ignored when stZeroFLabelFontQuality is not High. Values less than 0.0 result in an error and are replaced with the default value.

Default: 0.0

stZeroFLabelFont

This resource of type NhlTFont specifies the font used to render the zero field label.

Default: 0

stZeroFLabelFontAspectF

This resource determines the shape of the zero field label characters. Values increasing from 1.0 result in characters that appear thinner. Values decreasing from 1.0 make the characters appear wider. Values less than or equal to 0.0 result in a WARNING message and a restoration of the default value.

Default: 1.3125

stZeroFLabelFontColor

This resource specifies the HLU color index used to render zero field label text.

Default: True

stZeroFLabelFontHeightF

This resource controls the height in NDC of characters used in the text of the zero field label. The character width scales proportionally, unless you also modify the aspect ratio using the stZeroFLabelFontAspectF resource. The zero label text height scales with changes to the viewport width, unless you explicitly set stZeroFLabelFontHeightF during the same call.

Default: <dynamic>

stZeroFLabelFontQuality

This resource of type NhlTFontQuality determines the quality of the font used to draw the StreamlinePlot zero field label.

Default: High

stZeroFLabelFontThicknessF

Sets the thickness of the line used to draw zero field label text. The value acts as a multiplier of a (device-dependent) unit thickness. This resource is ignored when the stZeroFLabelFont specifies a filled font (font indexes 21-22, 25-26, 29-30, and 33-37).

Default: 1.0

stZeroFLabelFuncCode

This resource of type NhlTCharacter sets the function code character that the low level utilities will use when parsing the zero field label string.

Note: the default function code was a colon (:) in NCL Versions 6.0.0 and earlier.

Default: ~

stZeroFLabelJust

This resource of type NhlTJustification, after constraint to an appropriate value based on stZeroFLabelSide, sets the justification of the zero field label annotation with respect to its base location. The PlotManager Location Control Model requires this resource to allow control of the zero field label consistent with other annotations.

Default: CenterCenter

stZeroFLabelOn

The StreamlinePlot object draws a zero field label annotation only when stZeroFLabelOn is set True and the ScalarField data are determined to consist entirely of zero magnitude vectors within the limits of the available precision.

Default: True

stZeroFLabelOrthogonalPosF

stZeroFLabelOrthogonalPosF sets the coordinate of the base location of the zero field label annotation orthogonal to the current stZeroFLabelSide and directed away from the center of the viewport. The PlotManager Location Control Model requires this resource to allow control of the zero field label consistent with other annotations.

Default: 0.0

stZeroFLabelParallelPosF

stZeroFLabelParallelPosF specifies the coordinate of the base location of the zero field label annotation parallel to the current stZeroFLabelSide and directed toward increasing NDC values. The PlotManager Location Control Model requires this resource to allow control of the zero field label consistent with other annotations.

Default: 0.0

stZeroFLabelPerimColor

This resource sets the HLU color index used to draw the perimeter of the zero field label box.

Default: Foreground

stZeroFLabelPerimOn

stZeroFLabelPerimOn is a boolean resource that determines whether StreamlinePlot will draw an outline around the perimeter of the box surrounding the zero field label. If set False, no outline will be drawn.

Default: True

stZeroFLabelPerimSpaceF

stZeroFLabelPerimSpaceF determines the spacing or margin between the text of the zero field label and the edge of the zero field label box as a fraction of the current label text height.

Default: 0.33

stZeroFLabelPerimThicknessF

This resource determines the thickness of the perimeter line around the zero field label box. The value acts as a multiplier of a (device-dependent) unit thickness.

Default: 1.0

stZeroFLabelSide

This resource of type NhlTPosition determines where to place the zero field annotation in relation to the sides of the plot object. The PlotManager Location Control Model requires this resource to allow control of the zero field label consistent with other annotations. Its value determines a coordinate system origin and the direction of the positional resources, stZeroFLabelParallelPosF and stZeroFLabelOrthogonalPosF. It also constrains the value of the stZeroFLabelJust appropriately. There are four settings, which behave as follows, unless stZeroFLabelZone is set to one of the special zones (0 or 1):

Top

The PlotManager locates the zero field label annotation relative to a line paralleling the top viewport boundary. stZeroFLabelOrthogonalPosF increases in the direction of increasing NDC Y-Axis values and is constrained to positive values. stZeroFLabelParallelPosF increases in the direction of increasing NDC X-Axis values. stZeroFLabelJust is constrained to BottomRight, BottomCenter, or BottomLeft.

Bottom

The PlotManager locates the zero field label annotation relative to a line paralleling the bottom viewport boundary. stZeroFLabelOrthogonalPosF increases in the direction of decreasing NDC Y-Axis values and is constrained to positive values. stZeroFLabelParallelPosF increases in the direction of increasing NDC X-Axis values. stZeroFLabelJust is constrained to TopRight, TopCenter, or TopLeft.

Right

The PlotManager locates the zero field label annotation relative to a line paralleling the right viewport boundary. stZeroFLabelOrthogonalPosF increases in the direction of increasing NDC X-Axis values and is constrained to positive values. stZeroFLabelParallelPosF increases in the direction of increasing NDC Y-Axis values. stZeroFLabelJust is constrained to TopLeft, CenterLeft, or BottomLeft.

Left

The PlotManager locates the zero field label annotation relative to a line paralleling the left viewport boundary. stZeroFLabelOrthogonalPosF increases in the direction of decreasing NDC X-Axis values and is constrained to positive values. stZeroFLabelParallelPosF increases in the direction of increasing NDC Y-Axis values. stZeroFLabelJust is constrained to TopRight, CenterRight, or BottomRight.

If stZeroFLabelZone is set to 0, The PlotManager locates the zero field label annotation relative to the viewport center. If stZeroFLabelZone is 1, the direction of the stZeroFLabelOrthogonalPosF is opposite to the specification given above. Also if the stZeroFLabelZone is either 0 or 1, stZeroFLabelJust is not constrained, and stZeroFLabelOrthogonalPosF may take on negative values.

Default: Bottom

stZeroFLabelString

Specifies the string to use when drawing a zero field label. The string may contain function codes.

Default: "ZERO FIELD"

stZeroFLabelTextDirection

This resource of type NhlTTextDirection specifies the direction of the text in the zero field label. There are two choices:

Down

Each character is placed below the previous character in the text string.

Across

Each character is placed to the right of the previous character in the text string.

These descriptions apply before rotation due to stZeroFLabelAngleF.

Default: Across

stZeroFLabelZone

StreamlinePlot implements the zero field label as an embedded annotation. stZeroFLabelZone specifies the PlotManager zone assigned to the zero field annotation. The PlotManager Location Control Model requires this resource to allow control of the zero field label consistent with other annotations. If stZeroFLabelZone is set to 0, the positional origin is the center of the plot viewport; otherwise it is on or outside one of the sides of the viewport.

If you create a StreamlinePlot object without an active PlotManager by setting tfPlotManagerOn False, then StreamlinePlot manages the zero field annotation by itself. In this case, the stZeroFLabelZone resource is not as meaningful.

Default: 0