AutoCAD 3D modeling allows you to create drawings using solid, surface, and mesh objects.
Solid, surface, and mesh objects offer different functionality, that, when used together, offer a powerful suite of 3D modeling tools. For example, you can convert a primitive solid to a mesh to take advantage of mesh creasing and smoothing. You can then convert the model to a surface to take advantage of associativity and NURBS modeling.
Solid Modeling
A solid model is a volume that represents a 3D object, and has properties such as mass, center of gravity, and moments of inertia. You can create 3D solids from primitive solids such as cones, boxes, cylinders, and pyramids, or by extruding, revolving, sweeping, or lofting closed 2D objects as shown.
You can also combine 3D solids using Boolean operations such as union, subtract, and intersect. The illustration below shows two solids that were extruded from closed polylines, and then combined by intersecting them.
Surface Modeling
A surface model is a thin shell that does not have mass or volume. AutoCAD offers two types of surfaces: procedural and NURBS. Use procedural surfaces to take advantage of associative modeling, and use NURBS surfaces to take advantage of sculpting with control vertices.
A typical modeling workflow is to create basic models using mesh, solids, and procedural surfaces, and then convert them to NURBS surfaces. This allows you to utilize not only the unique tools and primitive shapes offered by solids and meshes, but also the shaping capabilities provided by surfaces - associative modeling and NURBS modeling.
You create surface models using some of the same tools that you use for solid models: sweeping, lofting, extruding, and revolving. You can also create surfaces by blending, patching, offsetting, filleting, and extending other surfaces.
Mesh Modeling
A mesh model consists of vertices, edges, and faces that use polygonal representation (including triangles and quads) to define a 3D shape.
Unlike solid models, mesh has no mass properties. However, as with 3D solids, you can create primitive mesh forms such as boxes, cones, and pyramids, starting with AutoCAD-based products 2010 or later. You can modify mesh models in ways that are not available for 3D solids or surfaces. For example you can apply creases, splits, and increasing levels of smoothness. You can drag mesh subobjects (faces, edges, and vertices) to shape the object. To achieve more granular results, you can refine the mesh in specific areas before modifying it.
Use mesh models to provide the hiding, shading, and rendering capabilities of a solid model without the physical properties such as mass, moments of inertia, and so on.