9.5.2

236 • CHAPTER 7
OBJECTS MENU • NURBS • 237
Flip Normals
Flips (i.e. reverses the direction of) the normals of the Sweep NURBS. Usually, CINEMA 4D will point
the normals in the correct direction. However, with open contours it is not possible for CINEMA 4D to
know which way they should point. In this case, you can control the direction of the normals, either
by changing the direction of the spline or by enabling the Flip Normals option. This option does not
effect the caps, since their normals are always calculated correctly.
Caps and Rounding
Use these settings to add caps and/or rounding to the Sweep NURBS. The Caps and Rounding settings are
described later in this chapter.
Troubleshooting tilted contour splines
The most commonly encountered problem when using SweepNURBS is when the contour spline
appears to tilt or ip over for no apparent reason as it runs along the spline. The cause of this is
rooted in complex math. We won’t concern ourselves with the math here. Instead, take a look at the
examples below for the solution.
In blue: the contour spline and the path spline. In red: the rail spline.
Figure 1 demonstrates the typical problem: the contour spline suddenly changes direction. In Figure 2,
the Banking option has been enabled, only partially solving the problem by tilting the spline as it
travels along the path.
Figures 3 and 4 represent alternative solutions to the problem. In Figure 3, the X and Y measurements
for the contour have been swapped around and Banking has been enabled. Figure 4 demonstrates
how you can overcome the problem using a rail spline — there’s no need to enable Banking in this
case.