CREATING GAME ART FOR 3D ENGINES- P4

CREATING GAME ART FOR 3D ENGINES- P4: Iwish to thank the editing team at Charles River Media (Emi Smith,Karen Gill, Jennifer Blaney, and Jenifer Niles) for their help in gettingthis book publish-ready. Thanks, too, to my technical editor, MikeDuggan. Also deserving recognition are the guys who make the TorqueGame Engine available, GarageGames, who directly or indirectly madethis book and the accompanying CD possible. In particular, I want tothank Joe Maruschak at GarageGames for the great articles and forumanswers that have helped me and many others get a handle on this engine.I...
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CREATING GAME ART FOR 3D ENGINES- P468 Creating Game Art for 3D Engines Applying a Utility Material A utility material is a special material that helps you to accomplish a task but will not be part of the finished work. For unwrapping processes, checkered materials work well; sometimes these materials can take the form of different colored squares with numbers in the squares to help define relationships between the UVs and the model. To see a new material on the model, go to the display panel and, on the Display Color rollout, turn on the Shaded Material Color. Select your model, and then refer to Figure 3.13 to create a checkered material. Try to get into the habit of naming your materials; any name will do, but leaving default material names invites prob- lems later in the process, because you can end up with mixed-up materials. Just as you created a custom material in Chapter 1, create a custom material here. If you go to the Maps rollout and click on the None button to the right of Dif- fuse color, the Material/Map Browser launches. Double-click on Checker, and your screen should look like Figure 3.13. The number 1 in the figure indicates where the Checker map type is in the list, 2 indicates what changes you should make to the tiling values for the checker pattern, and 3 is a reminder that you can get back to the main material editor menu by clicking the Parent button. FIGURE 3.13 Creating a utility material to test the quality of the UVW mapping. Chapter 3 Unwrapping Game Art 69 Figure 3.14 demonstrates what the Material Editor looks like when you get backto the main menu. The numbers in the figure serve as reminders to Assign Materialto Selection and Show Map in Viewport. These two steps are necessary to see thecheckered material on the model. There is also a reminder in this screen shot tomake sure your Display Color is set to Material Color, rather than Object Color.FIGURE 3.14 Assigning the material to the model, and making sure it displays correctly. To see what was accomplished by properly mapping the top and the bottom ofthe cylinder with the Normal map, look at Figure 3.15. The version on the left iswithout the Normal map applied to the top and bottom UVs, and the version on theright is with the Normal map applied. Note the size and aspect of the checker pattern.What you want in a well-unwrapped model is a checker pattern that is as squareand consistent as possible. As you can see, the version on the left is “streaking.” Themap applies fine to the sides of the cylinder, but it streaks across the top, becausethose UVs have not been properly flattened. The top of the cylinder on the right hasa much more regular pattern and will lend itself well to the texturing in Chapter 4,“Texturing Game Art.”Correcting Flaws in the UVsIf you turn the cylinder around, you can spot a flaw; this same flaw is apparent in theEdit UVWs dialog box. The flaw is the presence of a seam where there shouldn’t be. In-side the Edit UVWs dialog box is a right-click menu that will allow you to stitch seams70 Creating Game Art for 3D Engines FIGURE 3.15 Before and after properly mapping the top and bottom. or to weld vertices. In most cases, stitching seams works quite well, but in this case, welding vertices works better. Make sure you are in Vertex sub-object mode in the Edit UVWs dialog box, and from the right-click menu, select Target Weld (see Figure 3.16). This allows you to position the mouse over one vertex and drag it to the neighboring vertex to weld the two together. A big W appears near the cursor to indicate you are in Weld mode. If all goes well, you should see the seam in the UVs disappear. FIGURE 3.16 Using a weld to repair a detached vertex. Chapter 3 Unwrapping Game Art 71Moving UV Vertices to Improve the MappingFigure 3.17 demonstrates the process of sizing the UV maps so that the checker sizesare as square as possible. This keeps the material from stretching when you apply itto your model. In this image, all the UVs have been moved back inside the dark bluesquare of the Edit UVWs dialog box. The blue square is your texture space, withinwhich all your textures must fit to be exported properly for texturing. FIGURE 3.17 Moving the vertices down to adjust the checker pattern on the model. In this shot, the model is in Vertex sub-object mode, and the top row of verticeshave just been moved down, improving the aspect on the checker pattern squares.The top and bottom UVs have been placed over each other to s ...