Create 3D Solids from Objects (Concept)

The DELOBJ system variable controls whether the objects you select are automatically deleted when the 3D object is created.

Convert Surfaces and Objects with Thickness to 3D Solids

You can convert the several types of objects into extruded 3D solids with the CONVTOSOLID command. These objects include closed polylines and circles with thickness, as well as watertight meshes and surfaces. For a complete list of objects that can be converted using this method, see CONVTOSOLID.

NoteYou cannot use CONVTOSOLID to convert different, contiguous objects into a 3D solid. However, you can achieve the same result by first combining them. Suppose you explode a 3D solid box into regions. Start by using CONVTOSURFACE to convert each region to a surface. Then use UNION to form a compound surface object. Finally, use CONVTOSOLID to convert the surface to a solid.

Convert Mesh to 3D Solids

When you convert mesh objects to 3D solids, the shape of the new solid object approximates, but does not exactly duplicate, the original mesh object. You can control the differentiation somewhat by specifying whether the result is smooth or faceted (SMOOTHMESHCONVERT). You can also specify whether the resulting faces are merged (optimized).

For example, if you convert a mesh box to a solid object, you have the following options (available on the Mesh Modeling ribbon):

Smoothed and optimized. Coplanar faces are merged into a single face. The overall shape of some faces can change. Edges of faces that are not coplanar are rounded.
Smoothed and not optimized. Each original mesh face is retained in the converted object. Edges of faces that are not coplanar are rounded.
Faceted and optimized. Coplanar faces are merged into a single, flat face. The overall shape of some faces can change. Edges of faces that are not coplanar are creased, or angular.
Faceted and not optimized. Each original mesh face is converted to a flat face. Edges of faces that are not coplanar are creased, or angular.

You cannot convert the following types of mesh objects to a 3D solid:

Mesh with gaps between faces. Gizmo editing can sometimes result in gaps, or holes between the faces. In some cases, you can close the gaps by smoothing the mesh object.
Mesh that has self-intersecting boundaries. If you have modified a mesh object so that one or more faces intersect faces in the same object, you cannot convert it to a 3D solid.

In some cases, mesh that is not eligible to be converted to a solid object can be converted to a surface.