Viewing Particle and Geometry Data

Particle physics simulations typically provide a wealth of information about each particle, for example its position in space, its velocity, and its energy. Some simulations produce elaborate “histories” for particles, i.e., records of events that happened to the particle throughout time. Furthermore, information about the physical geometry within which simulated events happen usually has to be provided as part of a simulation’s input, and summaries of this geometry may also be included in the simulator’s output. IViPP can visualize both particle and geometry data.

3.1 Particles

IViPP has two modes in which it displays particles. Use the “Particles” submenu in the “View” menu to choose the mode you want to use.

3.1.1 Normal (Point) Mode

Normal Mode will draw either the point where the particle is located, or a line that represents the trajectory of the particle.

You may find that particles drawn as points are too small to see well. You can change the size of the points with the “Set Point Size” command in the “Particles” submenu of IViPP’s “View” menu. This command produces the dialog shown in Figure 3.1. Choose one of the sizes offered in the dialog and click “OK,” or click “Cancel” to leave the point size unchanged.

Figure 3.1. Setting the size of particles drawn as points.

For particles with detailed histories (e.g., particles from MCNP PTRAC files or SRIM collision files), a particle’s trajectory represents its actual locations over time. Some files (e.g., SRIM transmit files), however, simply give a particle’s position and energy at one instant in time. For these files, a “trajectory” is merely a line starting at the particle’s position and heading in the direction in which it is moving; the line’s length is proportional to the particle’s energy.

3.1.2 Density (Voxel) Mode

Density Mode will draw colored cubes, where the color of each cube represents the density of particles located within that cube (based on the particle’s start point). If the color is closer to blue, there is a relatively low density of particles, and if the color is closer to red, there is a relatively high number of particles within that cube. This mode is useful because it does not actually draw each particle individually, so the rendering time is improved when there is a large number of particles. Also, visually, it can be easier to view a large number of particles in this mode. If the particles are very dense, it is difficult to see individual particles anyway.

The colors can be set using either a linear or logarithmic scale, corresponding to the two “Density” options in the “View → Particles” submenu.

3.2 Targets and Geometry

Some file formats, such as TRIM Range and MCNP Input, contain information about the geometry of the environment around a reaction. This geometry can be drawn in two modes: full geometry or wireframe geometry. For full geometry, IViPP draws a solid shaded shape to represent the geometry. For wireframe geometry, IViPP draws lines to outline the shape of the geometric structure. Geometry display can also be turned off completely. Use the “Geometry” submenu of IViPP’s “View” menu to choose between these modes.

Figure 3.2 shows an example of “full” geometry displayed with particle trajectories.

Figure 3.2. A visualization containing particle histories (bright red) and geometry (dark/dull reds).

In order to draw geometry, IViPP divides the space occupied by the geometry into small rectangular volumes. You can control how coarsely or finely IViPP divides space using the “Set Resolution” command in the “Edit” menu. This command causes the dialog shown in Figure 3.3 to appear. Use one of the radio buttons in the main part of the dialog to choose a resolution. Lower resolutions cause geometry files to open faster, but the displayed geometry may show gaps or jagged edges; higher resolutions reduce these problems, at the expense of files opening more slowly.

Figure 3.3. Setting geometry resolution.

After you change the geometry resolution, IViPP will reload any already-open geometry at the new resoution.

Notes for MCNP Users

IViPP can render much, but not all, MCNP geometry. Specifically, IViPP can handle cell definitions involving unions, intersections, and complements of volumes defined by surfaces or other cells. It recognizes the following kinds of surface: P, PX, PY, PZ, CX, CY, CZ, C/X, C/Y, C/Z, KX, KY, KZ, K/X, K/Y, K/Z, S, SO, SX, SY, SZ, BOX, RPP, RCC, SPH, HEX, TRC, ARB. Surfaces, but not cells, may be modified by transformations.

IViPP only draws non-void cells. IViPP colors cells according to their material. Each material has its own color. However, IViPP has a total of 36 unique colors available, so some colors will be repeated if there are more than 36 materials used in the input file.

3.3 Saving Screen Images

You can capture IViPP visualizations into image files using the “Picture” command in the “Save” submenu of the “File” menu. This command saves the image currently displayed in the visualization area of IViPP’s main window as a “PNG” format file. The “Picture” command presents a dialog with which you can indicate the file’s name and location.

3.4 Background Color

You can change the background color of IViPP’s visualization area with the “Set Background Color” command in the “Edit” menu. This command displays the color selector shown in Figure 3.4. To use this selector, click in the outer colored ring (or drag the white line around that ring) to set the basic color you want (technically, the “hue”). Click in the inner triangle (or drag the black-outlined dot within that triangle) to determine how bright/pastel/dark the color is (technically, the color’s “saturation” and “value”). You can also type numeric color values into the “Hue,” “Saturation,” and “Value,” or “Red,” “Green,” and “Blue” text fields, or use the upward and downward arrows next to those fields, to set the color. Finally, you can type a hexadecimal color value, or certain common color names (“red,” “green,” “blue,” “yellow,” “magenta,” “cyan,” “black,” and “white” are known to work) into the “Color name” field.

Figure 3.4. Selecting a background color.

Return to the table of contents.
Previous Chapter: Loading Particle and Geometry Data.
Next Chapter: Visual Interaction with Data.