StreamlinePlot class resource descriptions

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>

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

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

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>

stMinLineLengthF
THIS RESOURCE IS NOT YET IMPLEMENTED.

Default:

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

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

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

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.

Default: 2

stArrowStartStride
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 stArrowStartStride 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

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>

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.

Default: 0.0

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

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

Default: Foreground

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"

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

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 stZeroFieldAngleF.

Default: Across

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>

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

Default: 0

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

Default: True

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

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

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

Default: High

stZeroFLabelConstantSpacingF
Normally when stZeroFFontQuality 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 stZeroFConstantSpacingF. When stZeroFConstantSpacingF 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

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

Default: 0.0

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.

Default: :

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

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

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

Default: Foreground

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

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

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

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

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

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


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$Revision: 1.9 $ $Date: 1998/08/19 01:09:20 $