The "raster" paradigm is used by most CAM software for calculating tool paths, while most CAD programs follow a "vector" paradigm. When I refer to a "vector" paradigm, I'm including CAD models built with traditional vectors (lines, polylines, arcs), polygons, mesh surfaces, solids, etc. If those models are then to be machined, most CAM packages will follow the vectors directly for the tool paths. But if the CAD model consists of mesh surfaces, then at some point, the CAM program must perform a "rasterization" of that surface to calculate the tool paths. That rasterization process basically involves sampling the irregular mesh surface on a regular grid of points.
"VS3D" consists of two separate but linked programs - VS3D and VScad3. VScad3 is like a traditional vector-based CAD program. VS3D is different. It offers the ability to sculpt complex/detailed surfaces (and so VS3D is also a type of "CAD" program). But VS3D is also a "CAM" program.
The CAD tools offer both raster (VS3D) and vector (VScad3) paradigms. All machining in VS3D/VScad3 is done in the raster paradigm (VS3D). The act of exporting a CAD model from VScad3 to VS3D is essentially a rasterization of the CAD geometry into what I call a "Sculpture Grid". The Sculpture Grid is a very tight grid of XY points, with a surface height (Z) value at each point.
But what VS3D offers that many programs do not, is the ability to perform free-form "Virtual Sculpting" on the sculpture grid. This involves interactive techniques such as hammering, scraping, warping, embossing, etc.
In most cases, detailed relief surfaces are best designed directly in VS3D, rather than trying to build them with primitive polygon mesh objects. But they can be built in VScad3 (or imported into VScad3 as a DXF file) first, and then be exported (rasterized) to VS3D for tool path calculation.
VS3D has the ability to "trace" (contour) a sculpted surface. The traced area becomes the selected "Region". One of the VS3D tool path types is "Region Perimeter". So with those tools, it is possible to have vector-like engraving capabilty in VS3D. For example, it is possible to import a digital image into VS3D and convert image brightness to surface height. Then automatically trace (contour) parts of the image (surface) and follow those contours with a tool bit. Of course, it is also possible to machine the whole thing as a continuous surface using the traversal, spiral, radial, etc. tool path types.
So, for example, you could have a tiff image of a star shape. You could import the image, trace the star automatically, specify the desired physical size of the star, and generate a tool path to cut out that shape (with tool bit offsets automatically calculated based upon the specified radius of the tool bit). Or, a star could be constructed in VScad3 and imported into VS3D, rather than importing a tiff image.
Along the same lines, rather than cutting out the star shape, VS3D could generate the tool paths to pocket it out. And the bottom of the pocket does not have to be planar. It could be a sculpted surface.
For the next major release of VS3D (version 2.0), the top priority for new features is to add some more traditional vector capabilities. Imagine sculpting a free-form "raster" surface. Then lay some true vectors/polylines over it. Then generate a tool path which follows the precise XY coordinates of the vectors, but also rides atop the sculpted surface for the Z positions along those vectors.
Thanks, let me know if you have any other questions.