Barbs Overview:
The Barbs tab provides for the placement of an array of arrow glyphs in the scene, pointing in the direction of a specified vector field.
Vector field: The user must specify X, Y, and Z components of a vector field. These are all either 2D or 3D variables in the VDC, based on a 2D or 3D selector. The constant zero (0) is selectable as a component. Each arrow glyph has length and direction determined by the value of the vector field at the start of the arrow.
Barb Layout options:
- The barbs are arranged on a 0, 1, 2, or 3-dimensional grid, with dimensions specified by the X, Y, and Z dimension parameters. (Use 1 as the dimension if you do not want the grid to extend in that direction).
- The position of the grid is determined by the Barb rake which has center and size in user coordinates indicated in the Barb Layout Options. The grid will be centered within the extents of the rake with the edge barbs 1/2 grid cell from the edge of the rake, provided "Align to XY grid" is not checked.
- If Barb rake mouse mode is enabled, the Barb rake is visible and can be manually resized and repositioned.
- If the VDC is geo-referenced, the latitude and longitude of the lower-left and upper-right rake corners are displayed.
Barb Appearance options:
Users may select Barb color, thickness and length.
- By default, the Barb color will be a constant color. Starting with VAPOR 2.5, the Barb color can also be specified using a transfer function, applied to any variable of the same dimension as the Barb field variables. The Barb will be shown with the color and opacity determined by the transfer function of the selected "Mapped Variable" at the 2D or 3D coordinates of the Barb.
- The diameter of an arrow is the thickness parameter times the horizontal size of a voxel in the data.
- The length of a barb is determined by multiplying the magnitude of the vector field at the origin of the arrow times the barb length scale factor specified in this tab. By default the length scale factor is set so that the longest arrow is no longer than 0.1 times the horizontal extents of the scene. Move the length slider or set the scale factor to obtain the desired barb lengths.
