These are tips on using
NURBS to create models.
Objects and Sub-Objects
- In 3ds Max Design, a NURBS model is a single, top-level
NURBS object that
can contain a variety of sub-objects. Get in the habit of creating
a single object at the top level, then going immediately to the
Modify panel and adding sub-objects by using rollouts or the
- Sub-objects are either independent or
sub-objects use relational modeling to
build NURBS geometry that is related to other geometry. However,
understand that the more dependencies a model has, the slower interactive
- In general, point curves and surfaces
are slower than CV curves and surfaces. Trims are the slowest kind
of dependency, and texture surfaces are the slowest kind of dependent
- If a dependent sub-object doesn't change
during animation, you can improve performance by making the sub-object
independent after you finish creating it.
- You can use
NSurf Sel to
apply modifiers to a sub-object selection. However, before you do
so make sure that Relational Stack is on;
Relational Stack is
on the General rollout for NURBS models. Otherwise, NSurf Sel can
select only the Surface and Surface CV sub-object levels.
Converting Other Objects
Shortcuts, Snaps, and User
- Remember to turn on the
Keyboard Shortcut Toggle. While it is
on, you can use all the NURBS keyboard shortcuts.
- One of the most useful NURBS keyboard
shortcuts is H, which opens
the Select Sub-Objects dialog. This is a subset of the
Selection Floater that
you can use during sub-object creation as well as sub-object selection.
This is handy when sub-objects are crowded or hard to see.
A variant is Ctrl+H, which also displays the
Select Sub-Objects dialog, but lists only those NURBS sub-objects beneath
the mouse cursor position.
- There are special NURBS Snaps in the
and Snap Settings dialog (right-click
the 3D Snap toggle to display this). When you use NURBS snaps, turn
off Options/Axis Constraints; otherwise, snaps work only in the
Also, remember that snaps
work in a viewport only when you have made the viewport active.
And choosing your snap settings does not turn on
snaps. You must also turn on the
Snap Toggle button (on the status bar).
Snaps are especially
important when you create the curves for building
- Remember that without leaving the viewport,
you can right-click to display a
quad menu with
shortcuts for changing the sub-object level, creating some sub-objects,
and using some other edit commands.
- When you work with NURBS, there are a
lot of rollouts in the Modify panel. Minimize the rollouts you don't
need. For example, minimizing the Modifiers rollout helps unless
you're applying Modifiers, and minimizing the Surface Common rollout
is useful when you're creating U loft, UV loft, and 1-rail or 2-rail
- Don't set viewports to display edged
faces. Displaying edges is almost twice as slow as displaying a
simple shaded viewport.
- When drawing a CV curve, click three
times to get a sharp corner.
Be aware, however, that
multiple CVs increase the amount of calculation and therefore reduce
the performance and stability of your model. However, if you want
to use the curve to construct a U Loft, and so on, this is the best
- You can also create sharp corners by
fusing the ends of two separate NURBS curve sub-objects. This is
the recommended method if you aren't using the curves to construct
- While creating curves, you can turn on
the Draw in All Viewports toggle. This lets you draw curves in 3D.
Begin drawing a curve in one viewport, go to another viewport, and
If your mouse has a middle
mouse button, Alt+middle mouse
button lets you use
change a viewport's orientation while you are creating the curve.
- To create a transform curve along a specific
axis, turn on the appropriate axis constraints, and then Shift+move a copy of the transform curve.
Curves and Direction
- NURBS curves show their direction in
viewports. A small circle indicates the first vertex. If the curve
is closed, a plus sign (+) indicates the direction of the curve.
Be aware of curve direction
when you use curves to construct
U loft and
UV loft surfaces,
If the curves don't have the same direction, you can get strange
twisting. Make sure curves have the same direction before you construct
the surface. On the Curve Common rollout, the controls Reverse and
Make First let you control the direction of the curve, and where
its starting point or CV is located.
Another good way to make
sure curves are aligned is to draw one curve and then use Shift+Clone to create the others.
After creating the aligned curves, you can transform CVs to vary the
curves on which the surface will be based.
Curves on Surfaces and
Creating Blend Surfaces
- You can blend between curves or between
surface edges. (You can't blend from a trimmed edge. In that situation,
you are blending from the curve that trimmed the surface.)
- If you want a controllable tangent or
tension, you must blend to a surface edge or a curve on a surface.
Adjusting tension changes the flatness or "bulginess" of that end
of the blend.
When a curve and a surface
(or two surfaces) are near each other, sometimes it can be hard
to tell which edge you are selecting. To assist you, the currently
selected surface turns yellow, and the edge that will be used for
the blend turns blue. Make sure you have selected the right surface
before you choose the edge.
- If the edges you are blending have different
numbers of points (usually due to different surface approximation
settings), then sometimes rendering shows gaps between the blend
and the original surface. If this happens, go to the
rollout and increase the value of Merge
until the gaps disappear when you render.
The Merge setting affects
only the production renderer. It has no effect on viewport display.
- If you need a surface between only two
curves, use a
surface instead of a U loft. This is faster.
- If loft creation seems slow, make sure
the Display While Creating check box (in the
Surface rollout) is turned off.
- If the U loft doesn't come out as you
expected, try reparameterizing the curves. Click Reparam. at the
Curve sub-object level. This button is on the CV Curve rollout.
dialog, choose Chord Length reparameterization.
If a curve is dependent
or a point curve, first you will have to make it independent (this
also improves performance).
Curves that are made
of two joined curves have this problem more often than others. If
you have a joined curve as one of the curves to construct the loft,
reparameterize it before you create the loft, or set the curves
to reparameterize automatically.
- The Edit Curve button lets you directly
transform the CVs of a curve within a U loft or
without changing the sub-object level. Edit Curve also gives you
access to all the rollouts that control the curve. You can use Refine
or Make First, for example, without changing levels.
- To close a UV loft, you can pick the
first V curve again to make it the last curve in the loft. Sometimes
a seam is visible at this location in the UV loft.
Multisided Blend Surfaces
- If 3ds Max Design doesn't create the
fuse the CVs at the three or four corners. Snapping CVs to each
other doesn't always succeed, because of rounding off.
Multicurve Trimmed Surfaces
- Multicurve trimmed surfaces are the only
way to create a trimmed hole that contains sharp angles.
- In general, the default tessellation
settings aren't suitable for displaced surfaces. With these default
settings, displacement mapping can create an extremely high
face count, which performs very slowly. Change the surface approximation
to the lowest necessary resolution. A good rule of thumb is to start
with Spatial approximation and an Edge value of 20. If that is too
low, reduce the Edge value until the model looks as it should.
- Use the
world space modifier to convert the displacement
map into an actual displaced mesh so you can see the effect of displacement
in viewports. To make a displaced mesh copy of the NURBS model,
Connecting an Arm to a
- The easiest approach is to create a
curve on surface or
projected curve on the shoulder. Then
create the arm as a
For the last curve of the U loft, select the CV curve on surface
or the normal projected curve. Then turn on Use COS Tangents, which
makes the loft surface tangent to the other surface where the arm
joins the shoulder.
- If the blend appears twisted, use the
Start Point spinner to change the location of the first point of
the curves that make up the U loft surface.
- Another way to connect a U loft to another
surface is to project the last curve in the U loft onto the other
surface. Click Make COS to convert the projected curve into a curve
on surface, and then on the U Loft Surface rollout click Insert
to make the new curve on surface the last curve in the U loft. You
can scale the curve on surface or move its CVs to get the curvature
and blending you want.