![[A Sphere Selector with Marked Particles]](figures/figure_5_1.png)
Figure 5.1. A sphere selector (green) marking some particles (black).
As the name suggests, “selectors” allow users to pick out, or select, a subset of the data IViPP is displaying. Selected particles can be visually distinguished from unselected ones by highlighting the selected ones in black (see Figure 5.1). Unselected particles may also be hidden from view to simplify IViPP’s display. Users can save highlighted particles’ data to files, and can generate energy histograms for them. (Note that is currently highlighted, not just selected, particles that can be saved or histogrammed; some future version of IViPP may change this so that selected particles participate in saving and histogramming regardless of whether they are highlighted.)
There are two categories of selectors: volume selectors and energy selectors.
Volume selectors identify particles that lie inside or pass through a user-defined volume of space. IViPP displays volume selectors as translucent regions, as shown in Figure 5.1.
The energy selector selects particles whose energy is within a specified range. When the energy selector is used on particles with history, it will select particles that have an energy within the range at any point throughout their history.
To create a selector, choose the selector type you want from the “Selectors” submenu of IViPP’s “Tools” menu. As you create selectors, their descriptions will be listed in a selectors panel, as shown in Figure 5.2. You can also create a new selector by clicking on the page icon at the end of the row of tabs for existing selectors in this panel. If the selector panel becomes hidden under other windows, or you want to see it before creating selectors, use the “Selectors” command in the “View” menu. (The selectors panel has its page icon for creating a new selector even when no selectors exist, so making the panel visible via “View → Selectors” and then clicking this icon is another way to create the first selector.)
![[IViPP's Selector Control Panel]](figures/figure_5_2.png)
Every selector has an inside and an outside. For the volume selectors, these concepts have the obvious meaning: “inside” means the space inside the selector’s volume, and “outside” means the space outside that volume. For the energy selector, “inside” refers to energies between the selector’s lowest and highest energies, while “outside” means energies outside that range. A particle is inside a selector if the appropriate particle property (position or energy, according to whether the selector is a volume or energy selector) is ever inside the selector. Conversely, if the particle is never inside the selector, it is said to be outside the selector. The “Selection” portion of every selector’s display (see Figure 5.2) governs what IViPP does to particles that are inside and outside a selector. In both cases, the choices are to select (i.e., put particles into a “selected” state), deselect (i.e., remove particles from the “selected” state), or ignore (i.e., leave particles’ “selected” state unchanged).
In order to actually select particles, you must click the “Select” button in the middle of the selector display. The general protocol for using a selector thus consists of setting up the selector through the fields in the lower part of its display, setting how you want IViPP to handle particles inside and outside the selector, and how you want IViPP to display the results of selection, in the upper part of the display, and finally clicking “Select.” You can repeat this process multiple times; each time you click “Select” IViPP will make a new selection and update its display.
Combinations of selecting, deselecting, or ignoring particles inside or outside of selectors make it easy to perform certain actions and to combine multiple selectors. In particular…
| To… | Do This… |
|---|---|
| Select all particles | Click any selector’s “Select Inside” and “Select Outside” radio buttons and then click the same selector’s “Select” button. |
| Deselect all particles | Click any selector’s “Deselect Inside” and “Deselect Outside” radio buttons and then click the same selector’s “Select” button. |
| Select the particles in the union of two selectors | Click the “Select Inside” and “Deselect Outside” radio buttons for the first selector, then click its “Select” button. Then in the second selector, click the “Select Inside” and “Ignore Outside” radio buttons, and click “Select.” |
| Select the particles in the intersection of two selectors | Click the “Select Inside” and “Deselect Outside” radio buttons for one selector, then click its“Select” button. Then click the “Ignore Inside” and “Deselect Outside” radio buttons for the second selector followed by clicking its “Select” button. |
The check boxes in the “Display” area of a selector’s display control how selection affects the way IViPP draws particles. Check the “Mark Selected” box if you want IViPP to highlight selected particles by drawing them in black instead of in their normal color. Check the “Hide Deslected” box if you want IViPP to not draw deselected particles at all. You can combine these options if you wish (e.g., highlight selected particles and hide deselected ones, etc.)
Whenever the set of highlighted particles changes, text appears in the message area in IViPP’s main window. The total number of highlighted particles will be displayed, along with the percentage of particles highlighted.
The “Manage” part of a selector display contains two buttons that let you save the selector’s description to a file, and restore it from a file. Clicking on either of these buttons will produce a dialog with which you can choose the file to save to or restore from.
You manipulate selectors through their descriptions on the selectors panel. All currently active selectors appear on the same panel. To pick a selector to work with, click on its tab at the top of the panel.
The lower part of each selector’s display shows parameters peculiar to that type of selector (see the sections below for details).
The “Update” button applies the parameters currently shown in the lower part of a selector description to the selector (simply changing a parameter does not immediately change the selector, you must click “Update” for the change to take effect). When you update a selector, IViPP redraws it on the screen (if it is a volume selector), but does not actually select particles. This feature allows you to adjust a selector to be visually where you want it before selecting anything.
Click the “X” in the tab at the top of a selector description to destroy that selector and remove its description from the selectors panel. Note that destroying a selector will not deselect particles selected by that selector nor change how IViPP displays them (i.e., highlighted particles will still be highlighted, and hidden ones will still be invisible).
IViPP’s volume selectors are the sphere selector, the cone selector, and the disk selector.
The sphere selector is actually composed of two spheres, one inside the other (i.e., the selector might more accurately be called a shell selector). For a particle to be inside a sphere selector, its location must be inside the outer sphere, but outside the inner sphere. If you want to base selection on only one sphere, set the radius of the inner sphere to zero.
The sphere selector has 5 user-set parameters, as shown in Figure 5.3. The “X,” “Y,” and “Z” parameters set the location of the center point of both spheres. The two radius parameters control radii of the inner sphere and the outer sphere.
![[The Sphere Selector Display]](figures/figure_5_3.png)
The cone selector is, as its name suggests, a conical volume.
The cone selector has 7 user-set parameters, as shown in Figure 5.4. “X,” “Y,” and “Z” determine the location of the cone’s apex. “Height” is the length of the cone’s axis (i.e. the line from the cone’s apex to the center of its base). “Apex Angle” is the angle at which the cone opens.“Altitude” is the angle of the axis above the XZ plane, and “Azimuth” is the angle in the XZ plane between the cone’s axis and the positive X axis (measured clockwise as seen from the positive Y axis). All angles are in degrees.
![[The Cone Selector]](figures/figure_5_4.png)
The disk selector selects particles based on whether their paths pass through a disk. By setting its width to 0, you can collapse the disk into a circle, making this selector useful for selecting particles that pass through a circular area as well as particles that pass through a disk-shaped volume.
Figure 5.5 shows a disk selector’s description. “X,” “Y,” and “Z” are the coordinates of the center of one of the disk’s flat faces. “Radius” is the disk’s radius. “Altitude” and “Azimuth” define the disk’s orientation, by setting the angle between its axis and the XZ plane (altitude) and the angle in that plane between the disk’s axis and the X axis (azimuth, measured clockwise as seen from the positive Y axis). Both angles are in degrees, and the axis starts at point (X,Y,Z). Finally, “Width” is the distance between the disk’s faces, i.e., the length of the disk’s axis.
![[A Disk Selector]](figures/figure_5_5.png)
Energy selectors select particles whose energies (at any point in their history) lie within a range. You can specify the range in either of two ways: by its bounds, or by its center and a tolerance about that center. Figure 5.6 shows both ways of describing energy selectors. To indicate how you want to specify energy in an energy selector description, click either the “Tolerance” or “Range” radio buttons in the description.
Notice that both selectors in Figure 5.6 select the same energies: 5 ± 2 or, equivalently, energies from 3 to 7. Beware that the units of energy are whatever the simulation program that produced the particle data uses. For example, energies from MCNP are in MeV, but energies from other simulators may be in other units.
![[An Energy Selector in Both Tolerance and Range Modes]](figures/figure_5_6.png)
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