Chapter 14 Working with Meshes and Polys 429

Figure 14-28: A NURMS heart created with the MeshSmooth modifier

HSDS modifier

You use the HSDS (Hierarchical SubDivision Surfaces) modifier to increase the resolution and smoothing of a localized area. It works like the Tessellate modifier except that it can work with small subobject sections instead of the entire object surface. The HSDS modifier lets you work with Vertex, Edge, Polygon, and Element subobjects. After a subobject area is selected, you can click the Subdivide button to subdivide the area.

The Level of Detail spinner lets you move back and forth between the various subdivision hierarchy levels. When polygon subobjects are selected, you can also Delete or Hide them. The Adaptive Subdivision button opens the Adaptive Subdivision dialog box in which you can specify the detail parameters. This modifier also includes a Soft Selection rollout and an Edge rollout where you can specify a Crease value to maintain sharp edges.

Summary

Meshes are probably the most common 3D modeling types. You can create them by converting objects to Editable Meshes or Editable Poly objects or by collapsing the Stack. Editable Meshes and Editable Poly objects in Max have a host of features for editing meshes, as you learned in this chapter.

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More specifically, in this chapter you

Created Editable Mesh and Editable Poly objects by converting other objects or applying the Edit Mesh modifier

Discovered the features of the Editable Mesh and Editable Poly objects

Learned to select and use the various mesh subobject modes

Discovered the various modifiers that you can use with mesh objects

In the next chapter, you learn about modeling and working with patch objects.

Creating and

Editing Patches

Patches are a modeling type that exists somewhere between polygon meshes and NURBS. They are essentially polygon surfaces

stretched along a closed spline. Modifying the spline alters the surface of the patch.

In many ways, patches have advantages over the more common mesh objects. They take less memory to store, are easier to edit at the edges, and are easy to join to one another.

Introducing Patch Grids

Because patches have splines along their edges, a patch can be deformed in ways that a normal polygon cannot. For example, a polygon always needs to be coplanar, meaning that if you look at it on edge, it appears as a line. A patch doesn’t have this requirement and can actually bend, which permits greater control over the surface and makes it better for modeling things like clothes and natural objects like leaves.

Another key advantage of Patch objects is that they efficiently represent the object geometry. If you examine a mesh object, you’ll notice that they contain a discrete vertex at the intersection of every edge at the corner of every face. Patch grids, on the other hand, have a vertex only at the corner of every patch. Each patch can consist of several faces. This reduction of vertices makes patches much cleaner and less cumbersome objects to work with.

Creating a patch grid

Patches are named according to the number of vertices at their edges; for example, a Tri Patch has three vertices, a Quad Patch has four vertices, and so on. The default Quad Patch is made up of 36 visible rectangular faces, and the default Tri Patch has 72 triangular faces, as shown in Figure 15-1.

15C H A P T E R

In This Chapter

Creating patch grids

Editing patches

Working with patch subobjects

432 Part III Modeling

Figure 15-1: A Quad Patch and a Tri Patch

To create patches, select the Create Patch Grids Quad Patch or Tri Patch menu commands. This opens the Create panel. Select the Geometry category, and then select Patch Grids in the drop-down list. To create a patch grid, click in a viewport, and drag to specify the dimensions of the grid.

You can also use the Keyboard Entry rollout to create patch grids with precise dimensions. To use this rollout, enter the grid’s position coordinates and its dimensions and click the Create button. The X, Y, and Z coordinates define the location of the center of the grid.

The Patch Grid Parameters rollout includes Length and Width values and values for the number of Segments for each dimension (but only for the Quad Patch). A Segment value of 1 creates six rows or columns of segments, so the total number of polygons for a Quad Patch never drops below 36. Tri Patches do not have a Segments parameter. You can also select to automatically Generate Mapping Coordinates.

Newly created patches are always flat.

Tutorial: Creating a checkerboard

In this tutorial, we create a simple checkerboard. To keep the white squares separate from the black squares, we use Quad and Tri Patches.

To create a checkerboard from patch surfaces, follow these steps:

1.Right-click the Snap button on the main toolbar; in the Grid and Snap Settings dialog box that appears, make sure that the Grid Points option is enabled. Then enable the Snap button on the main toolbar (keyboard shortcut, S).

2.Select Create Patch Grids Quad Patch and, in the Top view, create a perfect square using the grid points. Click the color swatch in the Name and Color rollout, and select the color black.

3.In the Command Panel, click the Tri Patch button and drag in the Top view to create an equally sized patch to the right of the first object. Select the Tri Patch, click its color swatch, and change its object color to white.

Caution

With the Tri Patch’s object color set to white, telling when it is selected can be difficult.

4.Repeat Steps 2 and 3, alternating which color comes first until the entire 8×8 checkerboard is complete.

Tip	An easier way to accomplish the checkerboard would be to create the first two squares and
	then to use the Array dialog box to create the rest. Find out more about the Array dialog box
	in Chapter 7, “Cloning Objects and Creating Object Arrays.”

Figure 15-2 shows the completed checkerboard.