Fixing UVs: Add a Checkerboard

Even though you did a careful and neat job of unwrapping and organizing the UVs, there's still a chance that the isolated UV portions of the texture map are inverted (like looking in a mirror) or that texture coordinates are crossed (resulting in smearing), overlapped (causing a duplication of texture), or not properly relaxed

(causing bloating or shrinking of the texture). I can almost guarantee that at least one of the aforementioned scenarios exists in your setup, but it's not a huge ordeal—it just means we have to go back to 3ds Max and fix them. For the Hicks character, inversion is not a big deal, but we need to check for the other errors. When you apply a texture (such as a checkerboard texture) without UVs, you'll notice many of these problems (see Figure 6.1).

One outstanding way of detecting problems before you begin the texturing process is to set up a checkerboard map. By filling your texture map with a small checkerboard pattern and then applying the texture to the model, you will have a much easier time checking for errors. I like to fill the individual areas of my texture map with differently colored patterns to make a clear definition of what each of the UV sections are, and I also like to add some text to the area, which not only helps me to identify that area but displays an inverted map area, too. If inverted UVs exist, the text comes out backward.

To see what I mean, first fill in the individual UV sections of the base color layer on the texture map. I've saved a checkerboard pattern for you. Just load the checkerboard.tif file in Photoshop, located on the CD-ROM in the Chapter 6 folder. Then use the Lasso tool to create selections around the UV areas, and fill the selections with the different colored patterns using either Edit, Fill or the Paintbucket tool. Figure 6.2 shows my map. Finally, use the Type tool to position text on the separate UV

Figure 6.2 Fill the separate UV areas with different colored patterns.

areas, or put a nonsymmetrical symbol on them, so that if any particular area happens to be inverted, you'll be able to tell instantly.

Next, you need to apply the checkerboard texture to each of the various body parts. Check for any signs of smearing, overlapping, or unevenness. It is common to find the most noticeable flaws in the front of the face, where the density of the checkerboard map is less than its surroundings. This means that we should go back to the UV mapping and select the points in that area, relax them, or otherwise scale them up a bit so the coverage of the material map is even in that entire head section. Also, because we stretched and relaxed nearly all portions of the UV map, I don't expect to see any other problems with smearing (see Figure 6.3).

Within 3ds Max, select the mapped boot object and open the Material Editor. Select one of the sample slots and name it boot. Then click on the mapping square next to the Diffuse color (see Figure 6.4) and

Figure 6.3 Apply the checkerboard material to the torso, and check for signs of smearing, overlapping, or unevenness.

choose the Bitmap option in the Material/Map browser. In the File dialog box that opens, select the Checkerboard.tif image. Then apply the material to the boot object.

Figure 6.4 The Material Editor lets you apply materials and textures to scene objects.

2. With the top of both boots visible, do a quick render of the scene to see how the map aligns to the boots (see Figure 6.5). Then rotate the model until the bottom of the boots are visible, and rerender the scene.

3. Replace the texture maps on both boots with the standard yellow material by dragging the yellow material onto each boot object. Then select a new sample slot and name it legs. Add the checkerboard.tif map to the Diffuse color for this new material and apply it to the leg object. Then render the legs to look for any problems (see Figure 6.6). From the render, you can see that the left leg mapping is backward.

Figure 6.6 The render for the legs shows that the mapping on the left leg is backward.

Figure 6.5 The map alignment for the tops of the boots looks fine without significant stretching.

Figure 6.6 The render for the legs shows that the mapping on the left leg is backward.

Figure 6.5 The map alignment for the tops of the boots looks fine without significant stretching.

4. With the leg object selected, select all the faces for the UVs that correspond to the left leg, and select the Tools, Flip Vertical command in the Edit UVWs window. If you then rerender the legs, you can see that the problem is fixed (see Figure 6.7).

5. Drag the default yellow material from the Material Editor and drop it on the legs object. Then select a new sample slot in the Material Editor and name the new material torso. Click on the mapping button next to the Diffuse color swatch, and choose Bitmap from the Material/Map browser. Select the checkerboard.tif file from the File dialog box. Then drag the new material to the torso, and render the torso to see how the mapping looks (see Figure 6.8).

6. The front of the torso is Planar mapped, which includes the bullets on the front of Hicks' jacket. You need to separate these bullet UVs from the rest of the jacket. Also notice the set of polygons in the lower-right section of the abdomen that has some problems. Before diving into fixing these problems, check a render of the back of the torso (see Figure 6.9). On

Figure 6.7 After you flip the UVs for the left leg, the problem with backward UVs is fixed.

Figure 6.8 The checkerboard test texture is applied to the torso object.

Figure 6.7 After you flip the UVs for the left leg, the problem with backward UVs is fixed.

Figure 6.8 The checkerboard test texture is applied to the torso object.

the back, you need to separate the pack from the rest of the torso's UVs.

7. With the torso object selected, open the Modify panel and click on the Edit button to access the Edit UVWs window. Select all the UVs in the window, and click the Exp. Face Sel to Pelt Seams button. This selects a single bullet on the front of the torso. Click the Cylindrical button followed by the Best Align button. Then choose the Mapping, Unfold Mapping menu and click on the Cylindrical button again to exit mapping mode. Then select and drag the bullet mapping away from the rest of the UVs. Repeat this step for all the remaining bullets. You'll find that there are three different unfold mapping types. You can stack similar types on top of one another (see Figure 6.10).

Figure 6.9 The back of the torso reveals that the UVs for the pack need to be separated from the rest of the torso's back UVs.

Figure 6.9 The back of the torso reveals that the UVs for the pack need to be separated from the rest of the torso's back UVs.

Figure 6.10 Using the Unfold mapping method, you can separate each of the bullets from the rest of the UVs.

8. To separate the pack's UV on the back of the torso, select all the pack's faces and apply a Pelt mapping. Then stretch out the Pelt mapping. I've also separated the arms and divided the torso into halves using the front seam instead of the sides. The front seams run vertically in a straight line. (Creating a seam along the side would require a jagged seam.) The resulting mappings from the front seams are much cleaner, as shown in the test render (see Figure 6.11). On the back, you need to separate the pack from the rest of the torso's UVs.

9. Apply the default yellow material to the torso. Select a new sample slot in the Material Editor, and name the new material arms. Then apply the checker-board.tif test texture as the map for the Diffuse color, and drag the new material to both arms. After rendering, you can see that the mapping for the left arm is fine, but the right arm's mapping is stretched (see Figure 6.12).

Figure 6.11 After you've fixed several of the mapping problems, the rerendered test mapping looks much better.

Figure 6.11 After you've fixed several of the mapping problems, the rerendered test mapping looks much better.

10. To fix the stretching on the right arm, reset the UVs using the Reset UVs button and then drag the Unwrap UVW modifier from the left arm and drop it on the right arm. Then select and reapply the mapping for the different selections. The resulting mapping fixes the stretching (see Figure 6.13).

11. Apply the default yellow material to the arms. Select a new sample slot in the Material Editor and name the new material head. Then apply the checker-board.tif test texture as the map for the Diffuse color, and drag the new material to the head object. After rendering, you can see that the mapping for the front of the head is fine (see Figure 6.14).

Figure 6.14 The texture mapping for the front of the head is fine.

12. For the back of the head, one polygon that belongs to the helmet is mapped with the neck guard (see Figure 6.15). It is shown in red in the middle of the helmet. To fix this polygon mapping, select the problem face and separate it from the helmet mapping using the Tools, Detach Edge Vertices menu in the Edit UVWs window. Then move the polygon face close to the neck guard. After that, select the edge closest to the neck guard using the Edge subobject mode and choose the Tools, Stitch Selected menu. This attaches the problem face where it should be.

13. Apply the default yellow material to the head. Select a new sample slot in the Material Editor and name the new material eyes. Then apply the checker-board.tif test texture as the map for the Diffuse color, and drag the new material to the eye objects. After you render, the mapping for the eye is fine (see Figure 6.16). Some portions of the eye are hidden in the shadows and appear dark, but that's okay. With the correct light, the eyes will show up.

Improperly mapped polygon

Figure 6.15 One descending face is mapped to the helmet, but it should be part of the neck guard. You can fix this by detaching the polygon and stitching it where it should be.

Improperly mapped polygon

Figure 6.15 One descending face is mapped to the helmet, but it should be part of the neck guard. You can fix this by detaching the polygon and stitching it where it should be.

Figure 6.16 The mapping for the eye looks fine.

14. All the work spent applying test materials to the various body parts can be reused after you've completed the actual textures. Save the file with all the checkerboard textures applied as HICKS-textured.max. You'll reuse this file later in this chapter.

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