Designing realistic objects is fundamental to the virtual reality process. A series of sliders and buttons are used to set the size, shape, orientation and color of each element that comprises an object. For example, a tree is built by specifying a series of levels that represent the trunk, branches and leaves. Level one forms the trunk that's interactively sized until a designer is satisfied with the representation. Level two establishes the pattern of the major branches.
Subsequent levels identify secondary branching and eventually the leaves themselves.
In Figure 1, the major branching occurs part way up the trunk, and it's fairly evenly spaced. Angular positioning sets how often branches occur around the trunk or branch to which they're attached. Branches at the figure's third level, for example, form a fan instead of being equally distributed. Orientation describes how the branches are tilting. Note that lower branches droop down from the trunk, while upper branches are more skyward looking.