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.A planar projection, for instance, places the image on a flat sur-face, such as a poster on a wall.A cylindrical projection wraps the imagearound a cylinder such as the label on a soda can, or around a consecutiveseries of flat sides, such as a label on the front and side labels of a cereal 05_200505_Avg_ch05 9/5/03 11:30 AM Page 263Objects and Surfaces263Figure 5-18The Surface Editorin LightWave.Theicon at the topwill rerenderquickly to showthe changesmade in thescreens below.The surfaceattributes can benamed, saved,and reloaded.box.A spherical projection wraps the image around a sphere such as amap stretched around a globe or around all the sides and top of a cubicobject.In addition to photographs and static designs, the surface-mapping tech-nique can also be employed with designs that the computer generates fromrandom elements, designs we call procedural.Although pictorial mapsrepresent a large photographic image that is usually equal to or larger thanthe object on which it is cast, procedural mapping represents images thatare generated by the computer according to a mathematical formula andare usually much smaller than the host object.Procedural surface mapping includes several simple categories that maybe found in all animation programs.These include tiling (or bricks), whichtakes a small pattern and repeats it across the surface at programmableintervals.Checkerboard creates a pattern of alternating squares of twodifferent colors.Noise creates a random pattern of any two colors with fre-quencies as small as the pixel elements.Swirl or marble imitates the ser-pentine patterns of marble, and paint allows you to use common drawingtools to paint the surface of an object.Procedural surface mapping also includes a range of ever-developingeffects categories that continually stretch the imagination of animators.Wood was one of the first of these categories and included most of the 05_200505_Avg_ch05 9/5/03 11:30 AM Page 264Chapter 5264Time-Saving TipFront- and rear-projected image maps are useful for quickly creatingcomplex scenes.Imagine that you have a scene in which the camerawill move very little or not at all.In this scene, you want to place acomplex character that will take time to animate.You don t have timeto render the entire background scene, so instead you project a photo-graphic image.As long as the camera doesn t move too much, yourrear-projected image can appear to be a full-developed 3-D envi-ronment: an office, forest, cityscape, or kitchen.But what if you have to move the camera? In this case, you may stillbe able to take shortcuts using image projection.For instance, if youhave a camera traveling horizontally along a road, the backgroundelements will move horizontally in proportion to their distance fromthe camera.The distant mountains may not move at all.Relegatethem to a static rear projection.The forest, just a few miles away, maymove slightly.Make this on one front projection, with the sky cut awayto show the mountains behind.Some trees might be in a field betweenthe forest and the road.These can be individual front-projectionplanes that move horizontally in and out of the shot.Now, in the fore-ground of all of these projections, add your complex character runningalong, and the scene is complete in a fraction of the time you neededto make 3-D mountains, forest, and trees!species on the planet.In quick succession came others: dirt, rust, water-drops, rivets, veins, pestilence, you name it.Third-party suppliers offer libraries of textures and images designed tocreate specific surface textures.Plug-in programs from companies such asAlien Skin Software (www.alienskin.com) enable artists to use popular pro-grams such as Adobe After Effects and Photoshop to create textures andeffects that can be exported into any 3-D animation system.Soon artists began to develop their own textures and even copyrightedthem.Ron Thornton, one of the great pioneers in 3-D animation and a mas-ter craftsman of space vehicles, once created a texture map for the surfaceof a grimy, old battle cruiser that became, for years, the de facto texture fora generation of space animators.Eventually, artists demanded the capabil-ity to paint directly on their objects in 3-D space. 05_200505_Avg_ch05 9/5/03 11:30 AM Page 265Objects and Surfaces265Painting on the surface of a 3-D object is an effect included in some pro-grams or offered as a third-party plug-in.Painting is extremely useful increating organic models, such as character faces.In a 3-D painting program,the animator may choose any orthogonal view of the object, select a virtualbrush or drawing tool, a painting medium, such as paint or spray, and abrush size.Using the cursor tool, the artist then applies the paint to theobject and, in all views, the object changes appropriately to display thepainted effect.This effect can be stored as a surface, unfolded, and used asa flat object or even copied onto other objects.When procedural maps are used in 2-D mode, they appear only on the sur-face of an object.3-D maps penetrate the interior of an object to enablehigher degrees of creative flexibility [ Pobierz całość w formacie PDF ]