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vertex that lies along the outer edge of the leaf, and move its handles so the patch edge aligns with the background leaf’s border. If the handles move together, hold down the Shift key to move them individually.

7.Deselect the Vertex subobject mode. In the Surface Properties rollout, enable all the options, and set the Relax Value to 1.0 and the Iterations to 50.

This smoothes out the wrinkles in the patch.

Figure 15-13 shows the completed maple leaf patch (half of it, anyway). To complete this leaf, use the Mirror tool and add a spline object for the stem.

Using Modifiers on Patch Objects

	Several modifiers work specifically on patch objects. The Modifiers Patch/Spline Editing
	submenu contains most of these modifiers.
Tip	Many other modifiers work on patch objects. To see which modifiers work on patch objects,
	select the patch object and check the Modifiers menu to see which modifiers are enabled.

Figure 15-13: By repositioning the vertex handles, you can make the patch object match the leaf’s edges precisely.

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Patch Select modifier

The Patch Select modifier enables you to select patch subobjects, including Vertex, Edge, Patch, and Element. You can copy and paste named selection sets. The selection can then be passed up the Stack to the next modifier. The Patch Select modifier provides a way to apply a separate modifier to a subobject selection.

Edit Patch modifier

This modifier includes tools for editing patch objects. The features of this modifier are the same as those of the Editable Patch object. If you want to animate the features of an Editable Patch, use the Edit Patch modifier. You can even apply the Edit Patch modifier to an Editable Patch. The key benefit of the Edit Patch modifier is that it enables you to edit patch subobjects while maintaining the parametric nature of the object.

Delete Patch modifier

You can use the Delete Patch modifier to delete a patch subobject from a patch object. You use the Patch Select modifier to select the patch subobjects to delete, and you apply the Delete Patch modifier to the Patch Select modifier.

Using the Surface tools

The surface tools, which include the CrossSection and Surface modifiers, provide a way to model that is similar to lofting. The CrossSection modifier takes several cross-section shapes and connects their vertices with additional splines to create a spline framework. You can then use the Surface modifier to cover this framework with a skin.

Cross-	Lofting is accomplished with the Loft compound object. For more information on it, see
Reference	Chapter 17, “Building Compound Objects.”

CrossSection modifier

The CrossSection modifier and the Surface modifier are the key reason why the spline and patch modifiers have been combined into a single submenu.

The CrossSection modifier works only on spline objects. This modifier connects the vertices of several cross-sectional splines together with another spline that runs along their edges like a backbone. The various cross-sectional splines can have different numbers of vertices. Parameters include different spline types such as Linear, Smooth, Bézier, and Bézier Corner.

To apply this modifier, all the cross-section splines need to belong to the same Editable Spline object. You can connect them using the Attach button. The cross-section splines are attached in the order they exist, which can be a problem if you create them in a different order. Figure 15-14 shows a spline network that has been created with the CrossSection modifier.

Note	Editable Splines include a CrossSection feature that works just like the CrossSection modifier.

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Figure 15-14: The CrossSection modifier joins several cross-section splines into a network of splines ready for a surface.

Surface modifier

The Surface modifier is the other part of the surface tools. It creates a surface from several combined splines. It can use any spline network but works best with structures created with the CrossSection modifier. The surface created with this modifier is a patch surface.

Parameters for this modifier include a Spline Threshold value and options to Flip Normals, Remove Interior Patches, and Use Only Selected Segments. You can also specify the steps used to create the patch topology. After the surface is created, you can apply the Edit Patch modifier to further edit and refine the patch surface.

Note	If the structure is already created, you can create a surface from the splines by simply apply-
	ing the Edit Patch modifier.

Figure 15-15 shows the spline structure illustrated in the preceding figure with the Surface modifier applied.

Tutorial: Modeling a brass swan

Chapter 2 included a tutorial that added a background image of a brass swan to the viewports. In this tutorial, we use the CrossSection and Surface modifiers to create a swan based on these background images.

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Figure 15-15: The Surface modifier applies a surface to the cross-section spline network.

To create a brass swan, follow these steps:

1.Open the Brass swan.max file from the Chap 15 directory on the CD-ROM. This file includes the background images needed to create the swan model.

2.Select Create Shapes Ellipse and drag in the Top viewport to create a simple ellipse that is roughly the shape of the swan’s nose. Use the transform tools to move, rotate, and scale the ellipse to match the cross section of the background image.

3.Hold down the Shift key and drag the ellipse shape to the base of the swan’s nose to create a clone. Use the transform tools to align this clone to the background image in the Front and Left viewports.

Note Although background images have been loaded for the Top, Front and Left viewports, you really only need two viewports to align all the cross sections. In this example, the Top viewport is misaligned with the other two viewports.

4.Continue to create cloned copies of the ellipse shape and match it to each changing cross section in the background images.

5.For the base cross sections, right-click on the ellipse shape and select Convert to Editable Spline from the pop-up quadmenu. Then click the Refine button and click the lower-left and lower-right corners of the ellipse to add two new vertices to the shape. Select and right-click these new vertices and change their vertex type to Bezier Corner to make the bottom of their cross section shapes flat.

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6.Select the first cross section shape at the swan’s nose and convert it to an Editable Spline. Then click the Attach button and select each cloned cross section shape in order from the nose to the tail. This makes all the shapes part of the same Editable Spline object.

7.Choose Modifiers Patch/Spline Editing CrossSection to apply the CrossSection modifier to the Editable Spline object. Then choose Modifiers Patch/Spline Editing Surface to apply the Surface modifier. Next, enable the Flip Normals option to see the final space capsule. This command creates a surface that covers the spline framework. The surface that is created is a patch object.

Figure 15-16 shows the completed swan model. Using the surface tools to create patch objects results in objects that are easy to modify. You can change any patch subobject by applying the Edit Patch modifier and using the rollouts in the Modify panel.

Another way to create this swan model is to use the CrossSection feature for the Editable Spline and then apply the Edit Patch modifier to create the finished surface. This method is cleaner and involves fewer modifiers.

Figure 15-16: The brass swan was created using the CrossSection and Surface modifiers.

Cross-	Another common modifier that is used with patch objects is the PatchDeform modifier.
Reference	Learn more about this modifier in Chapter 30, “Animation Basics.”