LightWave 3D 8 Texturing phần 8 pptx

·····································UVMapping and Editing Texture Projections and Mapping These distortions are caused by the subdivision of the model and can - not actually be perfectly fixed, since they are an artifact of LightWave’s subdivision algorithm. So don’t worry about them too much. 13. If we zoom out of the model now and take a look at the entire thing, it becomes obvious that the whole map is a little too stretched along the y-axis. In the UV map, this is the v-axis, and we need to scale the map down along this axis to fix this. However, because of the nature of discontinuous UV maps in Light - Wave, we need to unweld the points in the model before scaling them; otherwise parts of the model are going to remain stuck in place. 14. Press Ctrl+u to unweld all your points. The model will look a bit odd in your viewport if you were displaying your model in Subpatch mode (Tab), so generally I just press Tab again to go to normal Polygon display mode. 15. Now go to your UV viewport, select all the polygons, and press the “h” key to activate the Stretch tool. Holding down the Ctrl key (to constrain the stretching to a single axis), squash the polygons downward to squash them along the v-axis. Squash the polygons until the squares in the tex - ture begin to look more square instead of rectangular. 341 Figure 15-35 Chapter 15 ··········································· Part 4 16. Press the “m” key to merge your points again before continuing. Of course this squashing altered some of the editing we did previously, but you don’t really need to worry all that much about it, because the squashing now on the neck is relatively minimal and is not likely to cause problems when you paint a texture for it later on. 17. Let’s now focus on the top of the head. Rotate your Perspective viewport so that the top of the head is visible. You’ll see some nasty pinching at the pole where the cylindrical map comes to a point. 342 Figure 15-36 Figure 15-37 ·····································UVMapping and Editing Texture Projections and Mapping To be honest, there is no real point in spending much time actually edit - ing this to fix it because you’ll more than likely cover this area with hair, using Saslite or Sasquatch, or even modeled hair. If you want the character to be bald, it would be better to create an additional planar projection along the y-axis (just a standard projection, no UV map necessary) of the top of the head, and blend the two textures together using an alpha channel or Falloff settings in the Texture Editor. So this pretty much concludes the process of editing the UV map for a head. Some people like to create additional projections for the ears as well, but that isn’t always entirely necessary, as ears generally don’t tend to have much texture detail on them. It’s up to you, and since you now have this model, you’re free to do with it as you please. Atlas UV Maps Using Atlas Maps Aaaah, the ever-tempting Atlas unwrap option. This often looks extremely alluring to use since it gives the impression of being an ideal option for any- thing. Let me quickly banish that idea. Although the idea of an atlas unwrap seems like a great one, more often than not the result is a disjointed mess, especially when unwrapping organic models. In my experience, this option is not really suitable for characters (or any organic objects, for that matter) unless you want to spend a really, really, really long time editing the map. The following image demonstrates the fragmented chaos that results from unwrapping a simple head object. 343 Figure 15-38 Chapter 15 ··········································· Part 4 Figure 15-39 shows the same map after about an hour of editing, and it still needs a lot more editing before it can be of any use. The fragmentation that occurs from unwrapping using the Atlas unwrap option makes it disastrous for anything other than structures such as build- ings, cars, or anything else that has mostly retained simple shapes (primitive shapes). The atlas unwrap does have one main advantage: It can be used to unwrap an entire object, regardless of the orientation of any part of that object. This is because atlas does not use an axis to unwrap; it simply flat- tens out the entire object along an arbitrary axis. Pretty cool! So basically, you do not have to worry about choosing the right axis along which to unwrap, depending on what sort of alignment the different parts of the model have. Instead, it is simply a matter of clicking to unwrap, and then dealing with the resulting map as it turns out. In the case of atlas mapping, editing is essentially the key to success, as the result of the initial unwrap is so very unusual. Atlas maps are always very fragmented, no matter what settings you use. Of course, as we know, editing is essential in all unwrapping methods, but in this case it takes on more importance since the initial unwrap is, in almost every case, totally unusable without extensive editing. This only really excludes extremely simple buildings, which, although they can definitely be improved by editing, can use the initial map obtained in many circumstances. When editing atlas unwraps, one tends to use tools such as Flip UV Point Map a lot, since many polys often become flipped when using this method. We explore all the UV editing tools in great depth in Chapter 16. 344 Figure 15-39 ·····································UVMapping and Editing Texture Projections and Mapping Making an Atlas UV Map To make an Atlas UV map, select the model that you wish to unwrap, click on New UV Map on the Map tab in Modeler, and select Atlas. You’ll notice that the Atlas UV mapping type has a different setup of options compared to the Planar, Cylindrical, and Spherical types. The Relative Gap Size option defines the distance between the fragmented sections of the map. Larger values will cause the sec - tions to be farther apart from one another in the map, but remember that since the entire map needs to fit into the square UV template that is a finite size, increasing this value also means that each part will be smaller in the UV map. If you want to paint really fine details into your textures, you are going to have to create much larger images for your textures since each part is so small within that map. The following image shows an unwrapped cube with a Relative Gap Size value of 20% (on the left) and one with a value of 80% (on the right). I have drawn over the map with bolder lines to make the details clearer. The Segment by Surface and Segment by Part options allow you to specify whether the discontinuities in the UV map will be positioned according to different surfaces or parts assigned to the model that you are unwrapping. For more information on discontinuous UVs, refer to Chapter 16. So if you have, for example, three different surfaces assigned to the model, you can choose to have the fragmentation defined by these different surfaces. The same would apply to any parts that you have created in your model (parts are groups of polygons that you can define under the View tab in Modeler). 345 Figure 15-40 Figure 15-41 Chapter 15 ··········································· Part 4 Atlas UV Map Tutorial: Unwrapping a Small Building This tutorial demonstrates the use of Atlas UV mapping to unwrap a small building. We will unwrap the outer walls first, and then do the inner walls. 1. Open the 4.2.4-small_house.lwo object from the companion CD-ROM in Modeler. 2. The roof and the walls are on two separate layers. Let’s go to the wall layer and concentrate on that one first. Select all the outer walls of the house. I have already assigned a separate surface to them for ease of selecting, so all you have to do is open the Polygon Statistics panel (hit “w”) when in Polygon mode (Ctrl+h), go down to where it says Surf, and select the Walls Outer surface. Click on the little + symbol to select the polygons to which this surface is applied. 346 Figure 15-42 ·····································UVMapping and Editing Texture Projections and Mapping 3. Go to the Map tab and click on New UV Map. Select Atlas as the Map Type and give it the name “outer walls.” Leave the other values as they are and click OK. 4. Change one of your viewports to UV Texture, and the map should automatically be displayed in the viewport. As you can see, all the walls are nicely flat in the UV template. 5. Open the Image Editor and load the _uv_checker.jpg image from the companion CD-ROM. 6. Open the Surface Editor, go to the Walls Outer surface, and open the Color Texture Editor. Change the default layer Projection to UV, select the “outer walls” UV map from the UV Map list, and load the checkerboard image. 347 Figure 15-43 Figure 15-44 Figure 15-45 Chapter 15 ··········································· Part 4 Make sure that your Perspective viewport is set to display textures, and you’ll see the checkerboard image applied to the model. The outer walls, as you can see in Figure 15-47, are almost perfect. If we look at the area immediately to the right of the doorway, we can see that the checkerboard image is slightly squashed in this area. 348 Figure 15-46 Figure 15-47 ·····································UVMapping and Editing Texture Projections and Mapping 7. These polygons are slightly too wide in the UV map so we need to use the Stretch tool to fix this. You will have to unweld the vertices before doing this though, as this area is discontinuous, so press Ctrl+u to unweld the points before using the Stretch tool. 8. Now select the polygons that we need to squash, go to the UV viewport, select the Stretch tool (“h”) and squash the polygons inward along the u-axis (horizontally) until the patterns become square instead of rectan- gular, as shown in Figure 15-49. 349 Figure 15-48 Figure 15-49 Chapter 15 ··········································· Part 4 Leave all the points in the UV map unwelded for now. At the moment, the walls in the map are not positioned alongside their correct counterparts. In other words, the walls in the UV map are not nec - essarily flanked by the walls that are actually next to them in the model. So ideally we need to arrange them correctly in the UV map to make the tex - ture painting simpler, since there will be fewer seams to deal with. 9. Let’s start with the door area and the piece of wall to its left. Select the polygons in this area. You’ll notice that in the UV map, these two parts of the wall do happen to lie alongside one another. In Figure 15-50 I have made the selection in the UV map bolder so that you can see more clearly what you need to be doing. 10. Move these out of the actual UV area so that we can start arranging things correctly. Move them up and position them above the actual UV map. When you select the polygons to move them, do so in Point mode (Ctrl+g) instead of Polygon mode. Moving the polygons around in Poly - gon mode sometimes leaves points behind. 350 Figure 15-50 [...]... because the entire model was unwelded, LightWave has assumed that all the pieces are separate, and so it has not kept them intact when it unwrapped the model 21 So press Ctrl+z to kill the UV map 22 Merge all the points in the model again by pressing “m.” Now create the UV map again, using the same settings I described in step 19 Ahh, that’s much better Figure 15- 58 354 · · · · · · · · · · · · · · · ·... painting your textures so much simpler and straightforward But before we look at the actual nitty-gritty of editing UV maps, it’s important to understand how UV maps in LightWave actually work Understanding Discontinuous UV Maps UV maps in LightWave are created in a discontinuous manner This means that when the polygons are unwrapped and flattened to create the UV map, areas where the model has become... encounter a strange phenomenon whereby you find little distortions on your surface when applying textures with UV maps This is a well-known problem with LightWave s subdivision surfaces, and is something that has no really efficient way of fixing Figure 16- 28 shows examples of this distortion I have circled some of the areas affected by this problem, and as you can see, the texture has little jiggles in... · · · · · · · Part 4 Figure 15-64 And that’s atlas UV mapping A lot of moving things around and rearranging, but useful for situations like this 30 Merge your points by pressing “m.” And that’s it! 3 58 Chapter 16 Map Transformation and Editing Tools UV Map Editing Tools Of course, creating UV maps is not just about unwrapping the model and taking it into Photoshop (or whatever paint package you are... UV mapping tools General Commands The first bunch of options we encounter under the Map tab are basically just the usual Copy and Delete and Rename functions that we are accustomed to elsewhere in the LightWave package, as well as a couple of other, perhaps unfamiliar terms You can click on the Edit Maps and More buttons to access a few other commands as well Let’s look at each of them, one by one Figure... absolutely no mathematical abilities whatsoever (I can barely count over 10), I have a little trouble really fully understanding this tool’s function and usefulness since the explanation of it in the LightWave manual left my brain reeling somewhat However, after researching it a little, I have a decent explanation of it for you This tool affects points in a region of your UV map that you specify by... that shouldn’t be distorted (although this isn’t all that likely to happen) Using the UV Mapping Tools Under the Texture heading on the Map tab, we find the tools for creating and editing our UV maps for texturing New UV Map Obviously, this particular function creates a brand new UV map for the currently selected polygons or object in Modeler Clicking on the button opens a window from which you select... Map Type drop-down you can select the type of projection that you wish to use for your UV map For more information on each of these projection Figure 16-9 types, take a look at Chapter 14 362 Figure 16 -8 · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · Map Transformation and Editing Tools Texture Projections and Mapping Once you have selected a type of projection, select the axis that you... with the other poly map tools) has really outgrown its usefulness, and I am guessing that the only reason it is still in the program is for the off chance that you may happen to be given a really old LightWave model to work with that uses them Otherwise, you can ignore it UV Spider This command is accessed from the More drop-down menu When you select a polygon, the UV Spider crawls along and adds a... polygons were selected and the tool was activated In the UV viewport you can now see the entire row (edge loop) of polygons following those selected polygons has been added into the UV map Figure 16- 18 You will notice that the polygons are stretched to fill the entire space of the UV map, but this can be adjusted using the settings for the tool At the top of the panel, where it says Vertex Map, you . subdivision of the model and can - not actually be perfectly fixed, since they are an artifact of LightWave s subdivision algorithm. So don’t worry about them too much. 13. If we zoom out of the. demonstrates the fragmented chaos that results from unwrapping a simple head object. 343 Figure 15- 38 Chapter 15 ··········································· Part 4 Figure 15-39 shows the same map. shows an unwrapped cube with a Relative Gap Size value of 20% (on the left) and one with a value of 80 % (on the right). I have drawn over the map with bolder lines to make the details clearer. The