Meshes and Surfaces - Autodesk AutoCAD 2013 Practical 3D Drafting and Design - page 410

6. Activate the 3D-Roofs layer. Applying the SURFBLEND command, speci-
fy the CHain option and select an edge on the outer surface. Then, again
with the CHain option, select an edge on the inner surface and press
Enter to accept the blended surface.
7. To cut the parts of the straight surfaces that are inside the outer surface,
the SURFTRIM command should be applied. Select both straight sur-
faces, press Enter , and select the outer surface as cutting surface. Fin-
ally, mark on the parts of the straight surfaces that will be cut.
8. To create a roof on the entrance of the building, we need an extra surface.
Draw a line between top endpoints of the straight surfaces and extrude it
with -1 .
9. Now, apply the SURFPATCH command, selecting all edges that form the
closed loop, and confirm a flat patch surface.
10. Now delete the small extruded surface.
11. Finally, trim the outer surface with the SURFTRIM command, selecting the
outer surface, as cutting surfaces we select the straight surfaces and the
entrance roof, and specify the area to be trimmed.
12. Freeze the 2D layer.
13. Save the drawing with the name A3D_12_01final.DWG .