NAME ucd streak - generate surface constrained stream lines An experimental upgrade to the AVS5 "ucd_streamlines" module, Generate surface constrained stream lines stream lines / stream ribbons for a UCD vector field structure SUMMARY Name ucd streak (surface constrained streamlines) Type mapper Inputs ucd structure colormap field irregular 3-space float upstream transform Outputs geometry Parameters Name Type Default Min Max Node Data choice N Segment integer dial 16 2 64 Sample Style choice point N Steps integer dial 2 2 10 Integration choice 1st order Backward boolean off Color Streams boolean off Ribbons boolean off Ribbon Angle float dial 0.0 0.0 360.0 Ribbon Width float dial 0.1*max dim 0.0 20*default Interaction Mode choice Immediate Start Streams boolean off Max Steps int upper limit of steps per stream Boundary Constrain int stream or streak mode control Show Markers toggle show internal diagnostic markers for integration Boundary Only toggle show boundary flow without internal streamlines DESCRIPTION The ucd streak module is an advanced variation of the ucd_streamlines module in AVS5. It contains an optional mode where the streamlines follow the boundary of the flow domain, tracking along the surface, as long at the velocity field is into the boundary surface, and are not displayed when they leave the surface. This simulates oil drop streak lines from exterior flow wind tunnel tests. The flow is integrated through the 3D boundary elements, and optional integration step markers can be shown. Although the streamlines are only displayed at the surface, the whole interior 3D streamline calculation is taking place, so this method is quite different from a 2D surface only particle track algorithm. Any velocity component going into the boundary surface is projected back inside boundary cell a small fraction of a cell size away from the boundary, and another full 3D integration step is performed. The projection is performed normal to the boundary surface geometry. The zig-zag markers illustrate the boundary tracking algorithm, and show the last interior point, the integration step point outside the domain, the internal projection of cross-over, and the vertices of the cell face used in the projection. Additional controls allow the integration to be halted at a preset number of steps. No options have been removed from ucd streamlines, however the new boundary following algorithm and "ribbons" are mutually exclusive. StreamLine Basics: The ucd streak module generates colored stream lines or stream ribbons based on the vector node data in a UCD structure. The stream lines are generated at selected sample points. For every time step, ucd streak advances each sample point through space, based on the interpolated value of the node vectors surrounding the point. The result is a set of stream lines showing the progress of massless particles moving under the influence of the vector field at the nodes of the UCD structure. Stream ribbons behave similarly, except that their width and rotation also reflect the divergence and rotation of the flow at each point. The sample points can be any scatter field. Usually, they come from two sources: from a sample probe generated by the ucd streak module; or from arbitrarily-placed points defined by a field generated interactively by the create geom module. ucd streak's sample probe places a sample of points at a starting location in the UCD structure. The number of points is parameter- controlled. The sample probe's points can be moved around in space like any other geometry object, using the "virtual trackball" paradigm. To move the probe, select it by clicking on it, or by entering the Geometry Viewer and making it the current object. There are three different modes to initiate the calculation of stream lines: Immediate, Wait, and Button Up. In Immediate mode, any change to a parameter or probe displacement will cause stream lines to be calculated immediately. In Wait mode you must press the Start Streams button to initiate streaks calculation. This mode is useful when the streak calculation requires a long time and you want to change a parameter or move the probe without immediate calculation. In Button Up mode, you can move probe with the mouse, keeping the button down. When you set the probe in a proper position and release the button, the module will then calculate streaks. This mode can be useful when the streak calculation requires a long time and you want to move the probe without immediate calculation. A UCD structure consists of cells with nodes at their vertices. Each node may have data associated with it. Ucd streak only works with structures that have a vector component in their node data, thus it complains if the input structure has only scalar values at the nodes. (Scalar components can be converted to vector components with ucd extract vector.) If the nodes of a structure have more than one 3- vector component, use the Node Data radio buttons to select which component to use in calculating the stream lines. INPUTS UCD structure (required) The input structure is in AVS unstructured cell data (UCD) format. It must have at least one node component which is a 3D vector, representing the components of a velocity vector. colormap (required; colormap) An AVS colormap that is used by ucd streak to associate colors with vector values. Note that this is a regular AVS colormap, and not the color field output by ucd contour and ucd legend. Data Field (optional, field irregular 3-space float) ucd streak generates its own data sampling probe that is manipulated from the geometry viewer module. Optionally, one can also input a field that defines an arbitrarily-placed set of sample points. This field is usually created interactively with the create geom module, but can be saved and reused as an AVS field. Upstream Transform (invisible, optional, autoconnect) When the ucd streak module coexists with the geometry viewer module in a network, geometry viewer feeds information on how the point, circle or other sample probe has been moved back to this input port on the ucd streak module. The two modules connect automatically, through a data pathway that is normally invisible. This gives direct mouse manipulation control over ucd streak's sample probe. PARAMETERS Node Data Selects which of the node's data components to display. A set of radio buttons shows the label attached to each node data component. Before the module receives data, the default ", , ..." is displayed. If there are no vector components of the node data ucd streak complains. If there are several vector data components, these buttons let you select which component to use in calculating the stream lines. If there is no node data in the structure "" is displayed on the button. N Segment Integer dial that controls the density of points in the sample set. Sample Style (radio buttons) Specifies the configuration of points from which stream lines are drawn: point, line, circle, or plane. N Steps Integer dial that specifies the number of time steps for which stream lines are computed within each cell of the UCD structure. As the number of time steps increases, so does the accuracy of the stream lines. Integration Method Selects the integration method used to advance sample points through space: 1st order uses an euler integration method, 2nd order uses a 2nd order Runge-Kutta method, and 3rd order uses a 3rd order Runge-Kutta method. Backward (boolean) If Backward is selected, stream lines are extrapolated in the opposite direction that the UCD structure's vectors are pointing. By default this switch is off. Color Streams (boolean) If Color Streams is selected, the stream lines are colored based on the magnitude of the interpolated vectors used to generate the stream lines. By default this switch is off. Ribbons (boolean) A toggle switch that turns on stream ribbons rather than stream lines. The default is off. Ribbon Angle (float dial) This control only appears if Ribbons is selected. It controls the initial angle at which the ribbon is drawn. By default, ribbons are drawn with their width parallel to the X axis. The range is 0 to 360; the default is 0. Ribbon Width (float dial) This control only appears if Ribbons is selected. It scales the width of the ribbon. The range and default shown on the dial is calculated based on the size of the UCD structure. The default is 0.1*the maximum dimension of the structure. The minimum is 0.0. The maximum is scaled to be 20 times the default. (Ribbon width will vary along its length according to the divergence of the flow at each node.) Interaction Mode (radio buttons) Selects a mode to initiate the calculation of stream lines: Immediate, SWait or Button Up. In Immediate mode, any change to a parameter or probe displacement will cause stream lines to be calculated immediately. In Wait mode you must press the Start Streams button to calculate streaks. In Button Up mode you can move the probe with the mouse, keeping the mouse button down. When you set the probe in a proper position and release the button, the module will calculate streaks. Start Streams (boolean) A boolean switch that initiates the calculation of stream lines in Wait mode. This button allows you to manipulate the sample probe until you are satisfied with its position, or change other parameters and only then begin computing stream lines. OUTPUTS Stream Lines, Sampling Object (geometry) ucd streaks outputs two geometries: a set of colored disjoint lines or ribbons, and the sampling object. EXAMPLE 1 The following network reads in a UCD structure with a 3-vector float value as one of the components of the node data. ucd streak displays colored stream lines. Note that the module ucd to geom is used to provide a frame within which to view the streaks. To do this, select the "External Edges" parameter in the ucd to geom module GENERATE COLORMAP READ UCD | | |---------------| |-----------| | | | UCD STREAMLINE UCD TO GEOM | | |--------------| | | GEOMETRY VIEWER EXAMPLE 2 This network is identical to the first, except that the sample points are taken from a field that was originally generated with the create geom module. This field could have been saved with write field, in which case read field would replace create geom in the network. GENERATE COLORMAP READ UCD | | |-------| |-----------| | | | CREATE GEOM | | | | | | | |----------| | | | UCD STREAMLINE UCD TO GEOM | | |-----------| | | GEOMETRY VIEWER RELATED MODULES Modules that could provide the UCD structure input: read ucd field to ucd Modules that could provide the Colormap input: generate colormap Modules that could provide the Data field input: create geom read field Module that perform the same basic integration: ucd streamline Modules that can process ucd streak's output: geometry viewer ucd_particle