Autodesk 12812-051462-9011 User Guide 3 - Page 1727

a solid object. In a cube, for example, there is seldom the need to view the inside surface of any of the six squares that make up the cube. So for many viewing and rendering operations, 3ds Max ignores a face if it's facing away (that is, if its face normal is directed away) from a point of view. When you create objects in AutoCAD, AutoCAD Architecture, or Revit, 3ds Max generally understands which way faces should be oriented and manages face normals accordingly. However, occasionally you may encounter linked drawing geometry that displays correctly in AutoCAD, AutoCAD Architecture, or Revit, but doesn't strictly respect face-normal conventions. This can make it appear as though elements visible in the drawing file are missing or appear "inside-out" in 3ds Max. If this happens, try one of these four options: ■ During file link or import of the DWG file, turn on the Unify Normals switch in either the Basic panel of the File Link Settings dialog or the Geometry Options group of the AutoCAD DWG/DXF Import Options dialog. ■ If the drawing is already linked or imported, assign a Normal modifier on page 1581 to the object that is not displaying properly. Turn on the Unify Normals switch to force all the normals to face the same direction. If the object then appears to be "inside-out," turn on the Flip Normals switch as well. ■ To render the faces correctly, turn on the Render Setup dialog on page 6067 > Force 2-Sided switch. Also, to display the faces correctly in the viewports, turn on Viewport Configuration dialog > Rendering Method panel on page 7818 > Force 2-Sided. ■ Apply a material with the 2-Sided switch turned on. NOTE Using the Force 2-Sided options can result in slower performance, particularly when rendering. Using either of the Unify Normals options is the preferred method of handling face normals. If you experience a high volume of face normal problems in a particular file, verify that the File Link Settings dialog on page 6998 > Weld switch is on, and then reload the drawing. Weld forces nearby faces to share edges and vertices. Welding can still result in groups of face normals that are flipped in 3ds Max, in which case, turn on Unify Normals as well. 6982 | Chapter 23 Managing Scenes and Projects