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FIGURE 33.17

The UVs are positioned to match the loaded bitmap.

Figure 33.18 shows the results of the plane mapping. After the map is applied to the plane and visible in the viewports, you can open the Edit UVWs window again and tweak the mapping coordinates.

Using the Spline mapping

Spline mapping uses a spline and its cross sections to define the mapping coordinates. Tubular objects created with the Loft compound object or with the Sweep modifier are typically very difficult to correctly map given they don't fit in any of the existing mapping constructs. They can be unwrapped, but these objects usually have a lot of polygons, and this makes it difficult to unwrap or to pelt map.

The answer to this tricky object type is to use the Spline mapping method. With this mapping method, you can select to align the map to circular or planar cross sections. You can also add different cross sections if the lofted object uses different cross sections. Spline mapping is selected from the Wrap rollout in the Command Panel.

Tutorial: Spline mapping a snake

Spline mapping works well for objects like tentacles, arms, and ropes that have strong bends that cause mapping to be distorted. It also works well for simple snakes coiled and ready to strike.

FIGURE 33.18

The logo map is positioned on the wing and spreads over to the ailerons also, even though they are separate parts.

To add a texture map to a snake so it follows its length, follow these steps:

1. Open the Snake.max file from the Chap 33 directory on the CD. This object was created using the Sweep modifier and includes a lot of polygons. Before converting to an Editable Poly and forming the head, I cloned the path used to create the snake, so a spline that runs along the snake's midline is also in the scene.

2. With the snake objects selected, choose the Modifiers⇒UV Coordinates⇒Unwrap UVW menu to apply the modifier to the snake. Notice how the checkerboard texture is stretched along the snake's neck and head.

3. In the Modify panel, select the Face subobject and drag over all the polygons in the viewport or use the Ctrl+A shortcut to select them all. Then click the Spline mapping button in the Wrap rollout. This opens a simple panel where you can choose the Pick Spline button. Then choose the midline spline in the viewport. Notice how the mapping is immediately updated and aligned to run along the length of the snake, as shown in Figure 33.19.

FIGURE 33.19

Spline mapping lets you align the mapped textures to follow the length of a selected spline.

Unfolding a loop strip

Another handy tool in the Wrap rollout is the Unfold Strip from Loop. This feature is enabled when Edge subobject mode is enabled and is best used with an edgeloop. Once an edgeloop is selected, clicking this button will separate the polygons adjacent to the selected edgeloop and stretch them out into a long straight set of rows, which makes it easy to paint a texture.

Note

When the Unfold Strip from Loop command is used, the scale of the strip will be made extra large. Use can use the Pack tool to fit the strip back in scale with the other UVs. •

Figure 33.20 shows an edgeloop selected from the snake mesh in the previous example. Then with the Unfold Strip from Loop command, the polygons that run along the entire length of the snake have been pulled away as a separate strip.

FIGURE 33.20

Loop strips are easily separated from the rest of the mesh with the Unfold Strip from Loop button.

Using Peel and Pelt Mapping

In addition to the flatten, normal, and unfold mapping methods, the Unwrap UVW modifier includes nifty mapping methods for automatically unwrapping the UVs called Peel and Pelt mapping. But, before we dive into these methods, we need to understand and divide the mesh using seams. Seams are the borders between the various UV clusters. They can appear along smoothing groups, material boundaries, and hard edges.

Creating seams

Seams should be located in areas of the model that aren't clearly visible. For example, if