3ds Max 9 Bible

Several modifiers work specifically on patch objects. The Modifiers Patch/Spline Editing submenu contains most of these modifiers.

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.

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 17.14 shows a spline network that has been created with the CrossSection modifier.

Figure 17.14: 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.

Figure 17.15 shows the spline structure illustrated in the preceding figure with the Surface modifier applied.

Figure 17.15: The Surface modifier applies a surface to the cross-section spline network

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.

To create a brass swan, follow these steps:

1. Open the  Brass swan.max file from the Chap 17 directory on the DVD. 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 need only 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 them to each changing cross section in the background images.

5. For the base cross sections, right-click the ellipse shape and select Convert to Editable Spline from the pop-up quadmenu. Then enable Vertex subobject mode, click the Refine button in the Geometry rollout, 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 Bézier Corner to make the bottom of their cross-section shapes flat.

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 swan model. This command creates a surface that covers the spline framework. The surface created is a patch object.

Figure 17.16 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.

Figure 17.16: The brass swan was created using the CrossSection and Surface modifiers

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.