Using BOVE

As this tool is rather specialized it doesn't take long to get to learn to use it. In this section I'll show you through the important steps needed to create BOVE objects.

Creating a New Object

Just click on the new document symbol or New in the File menu to create a new object. A dialog box is shown, asking you for the number of particles you would like to have. The number of particles is the same as the number of faces your object will have.

After clicking on Ok you are shown the particles distributed over the surface of the sphere. Their positions are not of importance at the start but BOVE places them in a spiral around the vertical axis (you can see this more visibly the more particles you have).

Note: You can rotate the object by clicking on it and dragging. Also note you can rotate the sphere automatically by selecting Set in Rotation from the View menu or by clicking the button.



Simulating Charged Particles

When you select Simulate Charged Particles from the Operations menu or click on the button you are presented with the following dialog box:

The first two buttons at the bottom start and stop the simulation and the third performs the tesselation The process of creating triangles from a system of vertices. and polygation In BOVE, this is the operation of making polygons from triangles and their midpoints. . The Time Step slider can be moved to adjust the time taken for each step before painting the new positions. The scale is logarithmic A linear scale (e.g. 1,2,3,4) is one where each increment represents the addition of a number. A logarithmic (e.g. 1,10,100,1000) scale is one in which each increment represents the multiplication of a number. so there is more control over the magnitudes of time step you are selecting.

The progress bar in the middle shows the logarithmic speed of the particles relative to their starting speed. This is useful to see how the particles are settling down in their equilibrium state when visual movement is less than the pixel definition of your monitor. The speed is also important to see how precisely the particles are positioning themselves and whether the precision is within order of the error in the floating point mathematics The mathematics used by computers to solve fractions and to be able to deal with very large numbers. used by the computer (BOVE uses 8-byte floats.) This can be seen when the speed of the particles flicker.



Tesselation and Polygation

Once you are happy with the particles' positions you can start tesselation and polygation. Click on the Tesselation button to do this. Depending on the positions of your particles, this operation may succeed or fail. The tesselator that BOVE uses is not sympathetic to wildy placed particles, and if you have not allowed the simulator to order the particles somewhat before performing tesselation then you will be shown this dialog ...

... which should be self-explanatory. Otherwise you are rewarded with this dialog:

 

Clicking on OK closes the dialog box and the Simulate Charged Particles dialog box. You won't be able to move the particles again (unless you create a new object) so the button is disabled. Also notice that all the following view buttons have been enabled:

The buttons toggle the view of the particles, the triangles, the triangle midpoints and the polygons. At the moment we can see the particles (in green) with the triangles (in red) drawn between them.

If you toggle the triangle midpoints view, you will see the midpoints of the triangles (in blue). These are above the centres of the triangles as they are fixed to the surface of the sphere.

Toggling the polygons button shows the polygons. These are made up from joining the midpoints of the triangles that share common vertices. (You may like to switch off the triangles to see this better.)

You may notice that the midpoints are not positioned at the centres (of mass) of the triangles but at positions equi-distant from each triangle's vertices. If this were not the case, the sides of the polygons would not lie in a plane and their faces would be curved.



Saving and Exporting to VRML

You can save your objects and your view of them by clicking on Save or Save As ... in the File menu, and open them with Open. These commands save your objects as *.bove files and are only of use for BOVE.

If, however, you want to use the object in other software then you will need to export it to a common modelling file type.

BOVE currently exports to VRML Virtual Reality Markup Language. Pronounced Vermal. A widely used scripting language for describing virtual worlds. BOVE only scratches the surface of the features VRML has to offer. 1.0 (*.wrl) files for viewing in any standard VRML browser or editing within a modelling package. There are a number free VRML viewers available on the internet, and most modelling software should be able to import VRML.

Note: If you want to save your object for later viewing in BOVE you must save them in .bove files, as there is no support for importing VRML files.



Changing the Visual Settings

More for your visual satisfaction than my pride (honest!) I have included a dialog bar attached to the right of the main window to change the look of the object.

Note: Before you spend hours perfecting the look of your object, please note that none of these are settings are written to the exported VRML files - just the *.bove files save this information.

Let's take a look at the visual settings dialog bar:

The bar has two parts; one for the lights used to render the solid views of the triangles and polygons, and the other for the lines that are drawn (that do not use lights).

Lights:

You have up to 4 directional lights. In the picture to the left you can see that we currently have one light checked and its color is red. To change the color of the light simply click on the colored box and select the color from the new dialog box you are shown. The white box on the right with the black line in it shows the direction of the light. You can rotate the direction of the light by clicking in the box and dragging just like you can with the rotation of the object itself.

Lines:

Along with the particles and the triangle midpoints, you can also view the triangles and polygons as lines. Click on lighting if you wish to see your objects as solids and click on lines to see them as wireframes.