Using Spline Modifiers

In the Modifiers menu is a whole submenu of modifiers that apply strictly to splines. You can find these modifiers in the Modifiers Patch/Spline Editing menu.

Spline-specific modifiers

Of the modifiers that work only on splines, several of these duplicate functionality that is available for Editable Splines, such as the Fillet/Chamfer modifier. Applying these features as modifiers gives you better control over the results because you can remove them using the Modifier Stack at any time.

Edit Spline modifier

The Modifiers Patch/Spline Editing Edit Spline modifier (mentioned at the start of the chapter) makes spline objects so they can be edited. It has all the same features as the Editable Spline object. The Edit Spline modifier isn't really a modifier, but an Object type. It shows up in the Modifier Stack above the base object. The key benefit of the Edit Spline modifier is that it enables you to edit spline subobjects while maintaining the parametric nature of the primitive object.

Spline Select modifier

This modifier enables you to select spline subobjects, including Vertex, Segment, and Spline. You can copy and paste named selection sets. The selection can then be passed up the Stack to the next modifier. The Spline Select modifier provides a way to apply a modifier to a subobject selection.

The Modifiers Selection Modifiers Spline Select modifier lets you select objects from any of the subobject modes available in the Editable Spline object. It also includes buttons for selecting subobjects based on the other subobject modes. For example, if you select Vertex subobject mode, then two buttons available in the Select Vertex rollout are Get Segment Selection and Get Spline Selection. Clicking either of these buttons gets all the vertices that are part of the other subobject mode.

You can also Copy and Paste selection sets using the Copy and Paste buttons.

Delete Spline modifier

You can use the Delete Spline modifier to delete spline subobjects. Another good use of this modifier is to hide splines that are used for other purposes. For example, when creating an animation path, you can apply this modifier to the path to hide it, but by removing this modifier, you can get back to the base spline at any time.

Normalize Spline modifier

The Normalize Spline modifier adds new points to the spline. These points are spaced regularly based on the Segment Length value. This provides a quick way to optimize a spline. Figure 14.35 shows a simple flower shape with the Spline Select modifier applied so you can see the vertices. The Normalize Spline modifier was then applied with Segment Length values of 1, 5, 10, and 15. Notice that the shape is changing with fewer vertices.

Figure 14.35: The Normalize Spline modifier relaxes the shape by removing vertices.

Fillet/Chamfer modifier

You can use the Fillet/Chamfer modifier to Fillet or Chamfer the corners of shapes. Fillet creates smooth corners, and a Chamfer adds another segment where two edges meet. Parameters include the Fillet Radius and the Chamfer Distance. Both include an Apply button. The results of this modifier are the same as if you were to use the Fillet or Chamfer features of an Editable Spline.

Renderable Spline modifier

The Renderable Spline modifier lets you make any selected spline renderable. The Parameters rollout includes the same controls that are available for Editable Splines including Thickness, Sides, and Angle values.

Sweep modifier

The Sweep modifier works just like the loft compound object, letting you follow a spline path with a defined cross section, except that the Sweep modifier is a modifier, making it easier to apply and remove from splines and shapes. Another benefit of the Sweep modifier is that it has several Built-In Sections available that you can choose or you can pick your own. The built-in sections include many that are useful for architectural structures including Angle, Bar, Channel, Cylinder, Half Round, Pipe, Quarter Round, Tee, Tube, and Wide Flange.

Using the Merge From File button, you can choose a shape from another file. You can also set the number of interpolation steps. The Sweep Parameters rollout includes options for mirroring, offsetting, smoothing, aligning, and banking the generated sweep. The Union Intersecting option causes self-intersecting portions of the path to be combined using a union Boolean command. You also can select to have mapping coordinates generated on the sweep object.

Tutorial: Plumbing with pipes

If you want to create a shape that renders in the scene, you can use the Renderable Spline option or you can apply the Sweep modifier. In this example, we apply the Sweep modifier to a line that defines the path of a bathroom sink drain.

To create a pipe that follows a spline, follow these steps:

1. Open the  Bathroom sink.max file from the Chap 14 directory on the DVD. This file includes a simple bathroom sink and a line that defines its drain path.

2. With the spline selected, choose the Modifiers Patch/Spline Editing Sweep menu command to apply the Sweep modifier.

3. In the Section Type rollout, choose the Cylinder option from the Built-In Section drop-down list. Then set the Radius value to 10.

Figure 14.36 shows the resulting sink complete with a drain created using a cylinder cross section.

Figure 14.36: The resulting drain pipe was created using the Sweep modifier.

Trim/Extend modifier

The Trim/Extend modifier lets you trim the extending end of a spline or extend a spline until it meets another spline at a vertex. The Pick Locations button turns on Pick mode, where the cursor changes when it is over a valid point. Operations include Auto, Trim Only, and Extend Only with an option to compute Infinite Boundaries. You can also set the Intersection Projection to View, Construction Plane, or None.

Using the Shape Check utility

The Shape Check utility is helpful in verifying that a shape doesn't intersect itself. Shapes that have this problem cannot be extruded, lofted, or lathed without problems. To use this utility, open the Utilities panel (the icon for the Utilities panel looks like a hammer) and click the More button. Select Shape Check from the Utilities dialog box list, and click OK.

Note 

The Shape Check utility is found in the Utilities panel and not in the Modifiers menu.

The Shape Check rollout includes only two buttons: Pick Object and Close. Click the Pick Object button, and click the shape you want to check. Any intersection points are displayed as red squares, as shown in Figure 14.37, and the response field displays "Shape Self-Intersects." If the shape doesn't have any intersections, then the response field reports "Shape OK."

Note 

You can use the Shape Check utility on normal splines and on NURBS splines.

Moving splines to 3D

Although splines can be rendered, the real benefit of splines in Max is to use them to create 3D objects and for animation paths. You can use splines in several ways as you model 3D objects including Loft objects and modifiers. One way to use splines to make 3D objects is with modifiers.

CROSS-REF 

Using splines to create an animation path is covered in Chapter 29, "Understanding Animation and Keyframe Basics," and Loft objects are covered in Chapter 18, "Working with Compound Objects." General information on working with modifiers is covered in Chapter 12, "Introducing Modifiers and Using the Modifier Stack."

Figure 14.37: The Shape Check utility can identify spline intersections.

Extruding splines

Because splines are drawn in a 2D plane, they already include two of the three dimensions. By adding a Height value to the shape, we can create a simple 3D object. The process of adding Height to a shape is called extruding.

To extrude a shape, you need to apply the Extrude modifier. To do so, select a spline object and choose Modifiers Mesh Editing Extrude, or select the Extrude modifier from the Modifier Stack drop-down list. In the Parameters rollout, you can specify an Amount, which is the height value of the extrusion; the number of Segments; and the Capping options (caps fill in the surface at each end of the Extruded shape). You can also specify the final Output to be a Patch, Mesh, or NURBS object. Figure 14.38 shows our capital Es that modeled the various vertex types extruded to a depth of 10.0.

Figure 14.38: Extruding simple shapes adds depth to the spline.

Tutorial: Routing a custom shelf

In Woodshop 101, you use a router to add a designer edge to doorframes, window frames, and shelving of all sorts. In Woodshop 3D, the Boolean tools work nicely as we customize a bookshelf.

To create a custom bookshelf using spline Boolean operations, follow these steps:

1. Open the  Bookshelf.max file from the Chap 14 directory on the DVD.

   This file includes a triangle shape drawn with the Line primitive that is overlapped by three circles. All these shapes have been converted to Editable Splines.

2. Select the shape, open the Modify panel, and select the Spline subobject mode (or press the 3 key) and select the triangle shape.

3. Select the Subtraction Boolean operation (the middle icon) in the Geometry rollout, and click the Boolean button. Then select each of the circles.

4. Click the Subtraction button next to the Boolean button (it's the middle one). Then select the triangle shape, and click the Boolean button. Right-click in the viewport to exit Boolean mode, and click Spline in the Modifier Stack again to exit subobject mode.

5. Back in the Modify panel, select the Extrude modifier from the Modifier drop-down list and enter an Amount of 1000. Select Zoom Extents All to resize your viewports and view your bookshelf.

Figure 14.39 shows the finished bookshelf in the Perspective viewport ready to hang on the wall.

Figure 14.39: The finished bookshelf created with spline Boolean operations and the Extrude modifier

Lathing splines

Another useful modifier for 2D splines is the Lathe. This modifier rotates the spline about an axis to create an object with a circular cross section (such as a baseball bat). In the Parameters rollout, you can specify the Degrees to rotate (a value of 360 makes a full rotation) and Cappings, which add ends to the resulting mesh. Additional options include Weld Core, which causes all vertices at the center of the lathe to be welded together, and Flip Normals, which realigns all the normals.

The Direction option determines the axis about which the rotation takes place. The rotation takes place about the object's pivot point.

Caution 

If your shape is created in the Top view, then lathing about the screen Z-axis produces a thin disc without any depth.

Tutorial: Lathing a crucible

As an example of the Lathe modifier, we create a simple crucible, although we could produce any object that has a circular cross section. A crucible is a thick porcelain cup used to melt chemicals. I chose this as an example because it is simple (and saying "crucible" sounds much more scientific than "cup").

To create a crucible using the Lathe modifier, follow these steps:

1. Open the  Crucible.max file from the Chap 14 directory on the DVD.

   This file includes a rough profile cross-section line of the crucible that has been converted to an Editable Spline.

2. Select the line, and select the Modifiers Patch/Spline Editing Lathe menu command. Set the Degrees value in the Parameters rollout to 360. Because you'll lathe a full revolution, you don't need to check the Cap options. In the Direction section, select the Y button (the Y-axis), and you're finished.

Figure 14.40 shows the finished product. You can easily make this into a coffee mug by adding a handle. To make a handle, simply loft an ellipse along a curved path.

Figure 14.40: Lathing a simple profile can create a circular object.

Bevel and Bevel Profile modifiers

Another common set of modifiers that can be used with splines and shapes are the Bevel and Bevel Profile modifiers.

Note 

Both the Bevel and Bevel Profile modifiers are not found in the Modifiers menu. To apply them, use the Modifier List found in the Modifier Stack. They are among the Object-Space modifiers.

Using the Bevel modifier, you can extrude and outline (scale) the shape in one operation. With the Bevel modifier, you can set the Height and Outline values for up to three different bevel levels. The Capping options let you select to cap either end of the beveled shape. The Cap Type can be either Morph or Grid. The Morph type is for objects that will be morphed. You can specify that the Surface use Linear or Curved Sides with a given number of segments. You can also select to Smooth Across Levels automatically. The Keep Lines from Crossing option avoids problems that may result from crossing lines.

The Bevel Profile modifier lets you select a spline to use for the bevel profile.

Tutorial: Modeling unique rings

If you were paying attention when we discussed primitive objects, you realize that you can create a simple ring using a Tube or Torus primitive object. If you want the ring to have a unique profile, then the Bevel and Bevel Profile modifiers are what you need.

To create a couple of unique rings with the Bevel and Bevel Profile modifiers, follow these steps:

1. Select Create Shapes Donut, and drag in the Top viewport to create two donut objects that are positioned side by side. Set the Radius 1 value to 80 and the Radius 2 value to 75 for both rings.

2. Select the ring on the left in the Top viewport, open the Modify panel, and select the Bevel modifier from the Modifier List drop-down list in the Modifier Stack. In the Bevel Values rollout, set the Start Outline to 0, the Height values for Levels 1,2, and 3 to 20, the Outline for Level 1 to 15, and the Outline value for Level 3 to −15. Then enable the Smooth Across Levels option.

3. Select Create Shapes Line, and draw a profile curve in the Front viewport that is about the same height as the first ring.

4. Select the donut shape on the right, open the Modify panel, and choose the Bevel Profile modifier from the Modifier List in the Modifier Stack. In the Parameters rollout, click the Pick Profile button and select the profile curve.

Figure 14.41 shows the finished rings.

Figure 14.41: Bevels applied to a shape can give a unique profile edge.

CrossSection modifier

The CrossSection modifier is one of two modifiers that collectively are referred to as the surface tools. The surface tools provide a way to cover a series of connected cross sections with a surface. It connects the vertices of several cross-sectional splines together with additional splines in preparation for the Surface modifier. These cross-sectional splines can have different numbers of vertices. Parameters include different spline types such as Linear, Smooth, Bézier, and Bézier Corner.

CROSS-REF 

The second half of the surface tools is the Surface modifier. You can find this modifier and an example in Chapter 17, "Modeling with Patches and NURBS." The surface tools are similar in many ways to the Loft compound object, which is covered in Chapter 18, "Working with Compound Objects."