The Surface modifier
generates a patch surface based on the contours of a spline network.
A patch is created wherever the segments of the interwoven splines
form a three- or four-sided polygon. The Surface modifier and the
CrossSection modifier, taken together, are referred to as Surface
Tools. They allow you to create complex or organic surfaces, like
the fuselage of a plane, or a three-dimensional character.
Applying the Surface
modifier to create a patch surface.
CrossSection modifier can
be applied before the Surface modifier to connect splines representing
cross-sections. Once the basic spline network is created and the
Surface modifier is applied, the model can be adjusted by editing
the splines using an Edit Spline modifier below the Surface modifier
in the modifier stack. Since the Surface modifier creates a Patch surface,
further refinements can be made to the patch model by adding an Edit
Patch modifier above the Surface modifier.
The bulk of the work
in using Surface tools to model lies in creating and editing splines
in an Editable Spline or Edit Spline modifier. One of the benefits
to modeling using splines and Surface Tools is the ease of editing
the model. At almost any stage of modeling, you can add a nostril,
ear, limb or body by simply adding splines. This lends itself to
a free-form approach to organic modeling: you have a mental image
of what you want, then you create and edit the spline network until
you are satisfied.
Surface Modifier Basics
- Create a spline object.
- Make sure that the Spline vertices form
valid three-sided or four-sided, closed regions. Vertices on splines
that cross one another should be coincident.
To make spline vertices
coincident, drag vertices over each other with 3D Snap turned on.
3D Snap must have the Vertex or End Point option turned on. With
3D Snap turned on, you can snap to vertices on existing splines
as you create new splines. You can also select vertices and use
the Fuse option in an Editable Spline to make vertices co-incident.
- Use the CrossSection modifier to connect
spline cross-sections, unless you plan on manually creating the
splines that connect the model's cross-sections.
- Apply the Surface modifier, then adjust
the weld threshold to generate a patch object. Ideally all spline
vertices that will form a patch surface are coincident; the Threshold
parameter allows patch creation even if vertices are not quite coincident.
- Optionally, add an Edit Patch modifier
to edit the patch surface.
Make a reference copy of the spline object,
then add the Surface modifier to the copy and edit the original.
As you edit the original spline object, patches appear on the reference
copy as splines form three-or four-sided shapes. This allows you
to view a shaded surface as you model.
You can take this a step
further and add a Mirror modifier to the reference copy. As you
create splines for one side of a head or body, the reference copy
displays an entire model.
Modeling with Surface Tools
There are two primary
methods of using the Surface modifier to create patch models.
Scooter: Splines form
cross sections of the body
One method of using Surface
Tools is to create splines that represent a model's cross sections,
then the CrossSection and Surface modifiers are applied to create
the patch surface.
Face: Spline network
based on front and profile reference images
Two intersecting texture-mapped
polygons are used as a reference to create a network of splines
manually. Drawing lines on the physical sculpture is used as an
added visual aid to position the splines in this case. The CrossSection
modifier is not necessary if you create the spline network manually.
As the spline network
is edited, the patch surface of the reference copy is updated dynamically.
This allows you to view a shaded patch model as you manipulate the
spline network, any surface anomalies can be spotted and corrected.
Sequence of images
showing the spline network, the patches created by the Surface modifier,
and a shaded view of an alien character.
Example: Understanding valid splines:
- In the Top viewport, use Create
panel (Shapes) NGon to create three
NGons: a three-sided, four-sided, and five-sided NGon, each about
100 units wide.
- Make sure that all the splines form one
object. Do this by applying
an Edit Spline modifier to one of the NGons and using Attach to
add the remaining NGon objects.
- Choose Modifiers menu Patch/Spline Editing Surface from the Modifier List.
Notice that the three-
and four-sided splines formed patches but the five-sided NGon did
not. The five-sided spline does not form a three- or four-sided
closed region. To make it a valid spline, a line must bisect the NGon
to form a three- and four-sided region.
- In the modifier stack, highlight the
Edit Spline modifier again. On the Geometry rollout, turn on Create
Line, then create a line that bisects the five-sided NGon.
The start and end points
of the line should overlap the vertices on the NGon. Being exact
is not critical; the Threshold parameter fuses spline vertices based
on their proximity.
- In the modifier stack, highlight the
Surface modifier again. Now the five-sided NGon is a patch object,
consisting of a quad patch and a tri patch.
NoteIf the spline object did not turn into a
patch, increase the Surface modifier's Threshold parameter until
the patches appear.
Example continued: Adjusting the shape
of the spline:
- In the modifier stack, expand
the Edit Spline modifier's hierarchy, and higlight the Vertex sub-object
- In the Top viewport, select the top vertex of
the five-sided NGon.3ds Max displays
two vector handles. You
can move these handles on any axis.
- On the main toolbar, turn on (Select
and Move), then drag the handles around in the Top viewport.
The shape of the spline
- Below the modifier stack display, turn
End Result On/Off Toggle).
The patch changes shape
to fit the spline.
Spline Options group
Determines the overall distance
that is used to weld the vertices of the spline object. All vertices/vectors
within the threshold of each other are treated as one. Threshold
uses units set in the
NoteSpline control handles
are also treated as vertices, so setting high Threshold levels can
produce unexpected results.
- Flip Normals
Flips the normal direction
of the patch surface.
- Remove Interior Patches
Removes interior faces
of an object that you would not normally see. These are the faces
created within the caps or other interior patches of the same type
of a closed polygon.
- Use only selected segs
Only segments selected in
the Edit Spline modifier will be used by the Surface modifier to
does not have to be left on in the Edit Spline modifier.
Patch Topology group
The steps field spinner determines
how many steps are used between each vertex. The higher the step
count, the smoother the curve you will get between vertices.