Game Character Development with Maya - page 64


In this chapter you have once again worked through the process of modeling a character, this time to build the imposing, more stylized creature, Grae. By now you should have a good grasp of modeling techniques, as well as the essential tasks associated with polygon modeling, joint creation, and binding. In addition, you should have a good idea of what to look for when optimizing your geometry.

Now that we have Kila and Grae modeled, we can proceed in a new direction and learn to apply mapping data and a texture.

    Chapter 8. Texture Preparation

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    THE KILA AND GRAE models are complete, but they need color to bring them to life. Before we can apply color to our geometry we must prepare the surface by applying UV data.

    Within each vertex that exists in your polygon model lies a UV point ("UV" for short), which stores 2D coordinates that correspond to specific pixels on your texture. When you create any primitive objects in Maya, UVs are assigned by default, but these UVs are often altered when further modeling occursmeaning that they need to be rearranged to look correct.

    We will begin this chapter by looking at ways to clean up the UV data, making it usable so that we can then apply a texture to our characters.

      Mapping Methods

      There are four main ways to apply UV mapping data to a polygon object: planar mapping, cylindrical mapping, spherical mapping, and automatic mapping. All of these involve projecting the data directly onto the objects surface.

      Planar mapping (Edit Polygons > Texture > Planar Mapping) projects UVs through a plane along one direction only onto a mesh. This method is ideal for mapping flat objects.

      As you can see in Figure 8.1, the front of the cube is mapped fine, but because we are using a planar map the texture is stretched along the sides. To fix this you would need to apply additional mapping to the other five sides.

      Figure 8.1. Planar mapping

      Cylindrical mapping (Edit Polygons > Texture > Cylindrical Mapping), as the name implies, projects the UVs inward through a cylinder onto the selected object (Figure 8.2). This will work best on the outer polygons but, as with the planar mapping, you will need to add further mapping to correct the top and bottom caps.

      Figure 8.2. Cylindrical mapping

      Similarly, spherical mapping (Edit Polygons > Texture > Spherical Mapping) projects inward through a sphere (Figure 8.3).

      Figure 8.3. Spherical mapping

      The three techniques mentioned so far have very similar options for altering the final projection. Let's have a look at some of the more common options, shown in Figure 8.4; these are for a planar projection but are also used on the other projections.

      • Keep Image Ratio will lock the aspect of the projection to that of the image you are applying it to.

      • Smart Fit will automatically fit the projection to the geometry. If turned off, the projection manipulator will be created at the world root.

      • Mapping Direction is a setting unique to a planar projection and the one you will use most often. This allows you to dictate which axis the projection should come from.

      • Image Center, Image Rotation, and Image Scale each adjust the position, orientation, and size of the projection.

      Figure 8.4. The options for Polygon Planar Projection

      The fourth and final mapping method is automatic mapping (Edit Polygons > Texture > Automatic Mapping). This will attempt to find the best UV layout for your mesh by projecting inward from a specified number of angles.

      Look at Figure 8.5, left, where we have a basic, low-polygon hand model. If we apply automatic mapping with the default options, our UVs will be laid out for us. You can see this in Figure 8.5, right.

      Figure 8.5. Automatic mapping applied to a basic hand model


      To see an object's current UV layout, simply select the mesh and go to Window > UV Texture Editor. In addition to seeing the UVs, you can also edit them; we will talk more about the UV Texture Editor later in the chapter.

      We will see how to use some of these mapping methods as we apply UV mapping to our characters, but first we need to prepare the geometry to make the mapping process easier.