CG_MakeSolid — Cast the geometry into a solid. No check is performed. To obtain a valid solid, the input geometry must be a closed Polyhedral Surface or a closed TIN.
geometry CG_MakeSolid(geometry geom1);
Availability: 3.5.0
            
            This method needs SFCGAL backend.
        
            
            This function supports 3d and will not drop the z-index.
        
            
            This function supports Polyhedral surfaces.
        
            
            This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).