Today's and future processor speed and memory size make voxel-based solid
modelling to an attractive alternative to other representations of geometry.
However, in particular manipulation of high-precision models at interactive
speed is still not immediately possible by known algorithms. In order to
cope with that problem we propose to decompose a voxel-based modelling system
into layers. The concept opens the possibility to apply less precise but fast
algorithms of manipulation and rendering which meet interactive requirements,
but also to produce voxel-models at the higher preciseness possibly required
by the application. With this concept in the background, we present a
fast, though slightly imprecise algorithm for the problem of updating a voxel
workpiece touched by a voxel tool interactively moved by the user along
a path with six degrees of freedom. Updating means that affected
workpiece voxels get or loose material, depending on the tool mode which can
be ``applying'' or ``removing''. On an SGI Octane MXE, interactive speed is
achieved for workpieces up to 400^3 voxels and tools up to 80^3 voxels.
