9

File Link Tips 419
Fi l e Li n k Ti p s
HerearesometipsforchoosingFileLinking
options and avoiding common pitfalls.
Link ed Data and Face-Normal
Conventio ns
Face normals (page 3–980) can be a source of
confusion when linking to AutoCAD, AutoCAD
Architecture, or Revit drawing files. In 3ds Max,
every face has a front and a back, corresponding
to the inside or outside surface of a solid object. In
a cube, for example, there is seldom the need to
viewtheinsidesurfaceofanyofthesixsquares
that make up the cub e. 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 m anages face normals accordingly. However,
occasionally you may encounter linked drawing
geometr y that displays correctly in AutoCAD,
AutoCAD Architecture, or Revit, but doesn’t
stric tly 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 dr awing is already lin ked or impor ted,
assign a Normal modifier (page 1–746) to the
object that is not displaying properly. Turn
on the U nify Normals switch to force all the
normals to face the same direct ion. If the object
then appears to be “inside-out”, also turn on
the Flip Normals switch.
• TurnontheForce2-SidedswitchintheRender
Scene dialog (to render the faces correctly),
andturnonForce2-SidedintheViewport
Configuration dialog (to d isplay the faces
correctly in the viewports.)
•Applyamaterialwiththe2–Sidedswitch
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 metho d of handling face normals.
If you are experiencing a high volume of face
normalproblemsinaparticularfile,youshould
verify that the Weld switch is turned on in the File
Link Settings dialog (page 3 –428),andthenreload
the drawing. Weld forces nearby faces to share
edges and vertices. This can sti l l result in groups
of face normals that are flipped in 3 ds Max so the
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 Files wi th Hi gh Number s of
Linear Line S egments
Two-dimensional elements in drawing files, such
as lines, polylines, circles, and a rcs, 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 segments. There are two
ways these elements can be left out of your 3ds Max
scene;