Building and Editing Shapes

Once a shape has been initialised, the 2-D grid in which it can be built becomes accessible on the Edit panel. Basically one needs only three tools to create any shape, but some more features are added to make life easy. All these are on the toolbar right above the 2-D grid (Figure FigureToolbarGrid). The first four buttons are the basic drawing tools and colouring tool. These are all toggle buttons, meaning that enabling one will disable the others. They affect the presence and/or the state and colour of the voxels drawn by clicking in or dragging over the cells in the 2-D grid.

Figure: Toolbar and 2-D grid für cube space-grid

Next come two toggle buttons that allow you to select the drawing style. This is the way the basic drawing tools will respond to dragging the mouse over the grid cells. Finally, a series of compound drawing tools follows. These extend the range of the basic drawing tools and can all be cumulatively added to them.

Keep in mind that the grid looks differently for each space-grid. And for some spacegrids this 2-D grid is meant mainly for information as editing sphere shapes with the 2-D grid can be troublesome and with the rhombic grid is close impossible to properly edit a shape with the 2-D grid. That is why all shapes can be directly edited within the 3-D viewer. But nevertheless, the 2-D grid has its merits.

Navigating in 2-D and 3-D

Building and editing can take place exclusively in the 2-D grid, and then the 3-D viewport acts only as a visual aid. Both have their corresponding axes in the same colour: red for the x-axis, green for the y-axis and blue for the z-axis. For the 2-D grid, which actually can show only a single layer at a time, the z-axis is represented with a scrollbar (Figure FigureToolbarGrid). By default every new shape starts on the bottom layer and the scrollbar allows you to move up and down through the different layers along the z-axis (the number of z-layers is always indicated with the proper number of ticks along the scrollbar). Another way to navigate these z-layers is by pressing [+] (moves up one layer) or [-] (moves down one layer) on the keyboard.

Figure: Selections of grid cells in 2-D and 3-D

Moving the mouse cursor over the 2-D grid gives an indication of the cell(s) — depending on the state of the compound drawing tools — that will be affected by clicking. These indications are also reflected in the 3-D viewer. Furthermore, to facilitate positioning on different layers every non-empty voxel on the 2-D layer just below the current one 'shines through' in a very light shade of the default colour associated with that shape (Figure FigureNavigation). This makes building shapes from bottom to top very easy.

With larger grid sizes the cells of the 2-D grid can become very small, even when the available area for the grid on the Entities tab is maximised. To overcome this inconvenience the 2-D grid and the 3-D viewport can be exchanged. To do so, click the Toggle 3D item on the menu bar or press [F4]. Note that this affects only the position of the 3-D viewport for the Entities tab.

Basic Drawing Tools

The basic drawing tools affect the presence and/or the state of a particular voxel in the shape. In fact, together with the brush tool (→Brush Tool) they are all that's needed to create any shape in BURRTOOLS. The following is a description of these tools. Note that each is also accessible through a keyboard short cut.

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Fixed pen - Use this tool to draw normal or fixed voxels. Fixed voxels are represented by completely filled cells in both the 2-D and the 3-D grid (→ Representation). Remember that these fixed voxels must be filled in the final result. Keyboard short cut: [F5].

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Variable pen - This tool allows you to draw variable voxels. In the 2-D grid these variable voxels do not completely fill the cells, but have a narrow border showing the background of the grid. In the 3-D viewport the variable voxels have a black inset (→ Representation). Variable voxels instruct the solver that these particular places may be either filled or empty in the final result. So variable voxels are allowed only in result shapes, and the solver will give a warning whenever it encounters any variable voxels in a shape used as a piece. Short cut: [F6].

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Eraser - The eraser will remove voxels from the shape. Note that clicking or dragging with the right mouse button has the same effect of erasing voxels. The eraser tool however proves its use in minute adaptations of shapes. Short cut: [F7].

Drawing Styles

BURRTOOLS has two different drawing styles. These styles affect the way voxels are drawn/erased or colours are added by dragging with the mouse. In drawing shapes by simply clicking 'cell-by-cell' both are equivalent.

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Rectangular dragging style ('rubber band') - On dragging over the 2-D grid with the mouse, a rectangular selection of cells will be made. This is shown with a heavy border around the selected cells and the voxels will only be altered on releasing the mouse button. But releasing the mouse button outside the actual grid will make the whole operation void and can serve as a sort of 'undo'. This style is useful not only for drawing rectangular shapes or parts, but also for adding colour to (large areas of) the shape.

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Free dragging style - All drawing and colouring operations will be performed on a single cell basis and as soon as the mouse cursor is dragged over that particular cell. This drawing style is very useful for creating complex and irregular shapes and colour patterns.

The status of these drawing styles is remembered by BURRTOOLS so that it always defaults to the drawing style that was active on the last shut down of the program.

Compound Drawing Tools

Although the basic drawing tools are all that is needed for creating shapes, some compound drawing tools are added to speed up the process. The compound drawing tools can be added cumulatively to the basic drawing tools and only extend the range of action for the latter ones.

Note that these tools always function along the 3 orthogonal axes, so they are very useful for cubes but might need a bit of getting used to for the other spaces as they might behave differently along the 3 axes. The triangular prisms for example are stacked along the z-axis, side by side along the x-axis and tip by tip along the y-axis.

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Symmetrical drawing methods - For every voxel drawn, erased, or coloured its symmetrically placed counterpart (with respect to the centre of the grid and along one of the space axes) will be affected as well. Activating only one of these options will double the number of edited cells, whereas activating two or all three will affect respectively four times and eight times as many cells simultaneously. These options are not only useful for drawing symmetrical shapes, but they are also very well suited for finding the centre of the grid and (temporarily) setting the extents of a shape.

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Column drawing methods - These options — possibly combined with the symmetrical drawing tools — can really speed up drawing shapes as they will affect all voxels that are in the same row or column along one of the space axes. The number of voxels that will be affected depends on the size settings of the grid. Hence, to take fully advantage of these functions the grid should be first adjusted to the proper dimensions.

Using the 3D-Viewer to Edit

As editing non rectangular shape with the 2-D grid is cumbersome, it is also possible to do some editing using the 3-D view directly by simply clicking onto faces to add the corresponding neighbour voxel. This will always only add or remove single voxels and will not honor the compound drawing settings. The following actions are possible:

• Add a normal voxel by pressing [Shift] and clicking onto a face. The neighbour is added.
• Add a variable voxel by pressing [Alt] and clicking onto a face. Again the neighbour is added.
• Remove a voxel by pressing [Ctrl] and clicking onto a voxel. This removes the voxel.

As spheres do not really have touching faces the 3-D view of them does contain circles with a slightly different colour around the places where the spheres would tough. Clicking on those circles on the sphere adds the corresponding neighbour sphere.

To avoid having to click all that often you can wiggle the mouse around to get a repeated action. So if you want to "drill" a hole into a shape place your mouse there, click and drag over the hole and the voxels will be gone much faster than with repeated clicking.