8

428 Chapter 20: Managing Scenes and Projects
Fi l e L in k Ti p s
HerearesometipsforchoosingFileLinking
options and avoiding common pitfalls.
Link ed Data and Face-Normal
Conventio ns
Face normals (page 3–1074)
can be a source
ofconfusionwhenlinkingtoAutoCAD,
Architectural Desktop, or Revit drawing files.
In3dsMax,everyfacehasafrontandaback,
corresponding to the inside or outside surface of
a solid object. In a cube, for example, there is
seldomtheneedtoviewtheinsidesurfaceofany
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 A utoCAD,
Architectural Desktop or Revit, 3ds Max generally
understands which way faces should be oriented
and manages face norm a ls accordingly. However,
occasionally you may encounter linked drawing
geometr y that displays correctly in AutoCAD,
Architectural Desktop 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
BasicpaneloftheFileLinkSettingsdialogor
the Geometry Options group of the AutoCAD
DWG/DXF Import Options dialog.
If the drawing is already linked or imported,
assign a
Normal modifier (page 1–738)
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”, also turn on
the Flip Normals switch.
•TurnontheForce2-Sidedswitchinthe
Render
Scene dialog
(to render the faces correctly),
andturnonForce2-Sidedinthe
Viewport
Configuration dialog
(to d isplay the faces
correctly in the viewports.)
•Applyamaterialwiththe2Sidedswitch
turned on.
Note: Using the Force 2Sided options can result in
slower performance, particularly when rendering.
Using either of the Unify Normals options is the
preferred method of hand ling face normals.
If you are experiencing a high volume of face
normalproblemsinaparticularfile,youshould
verif y that the Weld switch is turned on in the
File
Link Settings dialog (page 3–435)
,andthenreload
the drawing. Weld forces nearby faces to share
edges and vertices. This can st il l result in groups
of face norma ls that are flipped in 3ds Max so t he
Unify Normals switch should also be used.
Note: Thedisadvantageofweldingisthatitcanbe
time-consuming when you attach and reload the
linked file. The time penalty is much greater when
3dsMaxiscreatingobjectsthathaveverylarge
numbers of individual faces.
Linki ng Fil es with H igh Numbers of
Linear L ine S egments
Two-dimensional elements in drawing files, such
as lines, polylines, circles, and arcs, are represented
as splines in 3ds Max. These splines carry much
moreinformationateachvertexthantypical
AutoCAD 2D structures. Since some drawing
files contain large quantities of 2D data, exercise
caution when linking files containing a high
number of discrete line seg ments. There are two
ways these elements can be left out of your 3ds Max
scene;
by freezing their layers in AutoCAD,
Architectural D esktop, or Revit b efore you start
3ds Max and b efore e ach subsequent reloading
process.