Creating Textures for Characters in Autodesk Maya* By Ryan Bird

Transcription

1 Creating Textures for Characters in Autodesk Maya* By Ryan Bird Texturing is the process of adding detail (color, bump, specular, and so on) to a 3D mesh. You typically add texture using 2D painting software, such as Adobe* Photoshop* or Corel* Painter*. Figure 1 shows two versions of the same model. The image on the left is an untextured mesh, while the image on the right is a textured mesh. Figure 1. The untextured and textured versions of the fairy model This article describes how to paint a color texture. I will be using the fairy model from my previous article, Creating UVs for Characters in Autodesk Maya. I use Autodesk Maya* and Photoshop* to complete the tasks.

2 2 Creating Textures for Characters in Autodesk Maya Does Size Matter? Depending on the media a model is used for, the size of the texture does matter. Texture maps for video games and real-time environments tend to be smaller in size and have limits determined by the engine they are being made for. In contrast, texture maps for pre-rendered sequences (film and broadcast) can be much bigger. Generally, the sizes of these texture maps are only limited by what the rendering computer can handle. Regardless of the size of a texture map s target, it s important that those maps look their best. For this article, I create a , game-friendly map for my low-resolution fairy model. UV Snapshot Before I begin painting the texture, I take a snapshot of the UVs (that is, the mesh s U and V coordinates). I do this so that I have a guide for what I m painting and know where everything needs to go. Maya* provides a way to obtain a UV screenshot without having to use the Print Screen option on the keyboard: I select the mesh objects included in the texture map, then, in the UV Texture Editor, click Polygons > UV Snapshot. The UV Snapshot window opens showing several options for saving an image for the UVs selected. Under File Name, I chose a location for the saved snapshot image and provide a file name. The Size X and Size Y fields define how big the snapshot image needs to be. Previously, I stated that my texture map size would be pixels, but that is not the size I enter. When I create texture maps for games, I always double the size of the map in case there is reason to have a higherresolution map later (box cover renderings, cinematics, or even for portfolio purposes). So, I set my coordinates to By default, the Image Format is set to Maya IFF. Although Photoshop* reads this format just fine, I prefer to use the TIFF format for the UV snapshot, because the file size is much smaller and the quality is the same. I click OK to save an image of my UV snapshot to my designated folder. Bringing the Snapshot into Photoshop I now go into Photoshop*. When I open the saved UV snapshot image from my designated folder, it looks similar to Figure 2.

3 Creating Textures for Characters in Autodesk Maya 3 Figure 2. The UV snapshot image in Photoshop* From here, I need to do a bit of preparation work on this image before it s ready to be painted. First, I get rid of the image s alpha channel. During the UV snapshot export process, Maya* includes an alpha channel with most file formats. If this alpha channel remains in the final texture and is saved as a TGA or TIFF image, the channel makes the mesh transparent when the texture applied to the mesh s material, showing only a textured wireframe. That s not to say that a custom alpha channel can t be added later; it s just good practice to get rid of the initial one. Next, I invert the image so that the black areas are white and white areas are black. I do this so that it will be easier to see what I m painting underneath this layer. To do this, I press Ctrl+I.

4 4 Creating Textures for Characters in Autodesk Maya That last part of preparation is to change this layer from a background layer to a multiplied layer that I can place over the texture, allowing me to use the UV snapshot as a guide to what I m painting. To do this, I double-click the Background layer in the Layers folder, which opens a New Layer window. I change the name to wireframe so that it is easy to keep track of. I change the Mode to Multiply and click OK. Changing this layer to Multiply allows me to see the UVs overtop the image that I m painting. Layers When painting a texture, I find it helpful to separate things into individual layers. Although it can be difficult to manage and keep track of many layers, the ability to refine and edit individual pieces makes it worth it. For example, having a separate layer for an eyebrow rather than painting it directly on the skin layer will make it much easier to edit if changes or fixes are required later on. That said, it s good practice to make sure there aren t too many layers. Redundant or useless layers will only make things confusing and frustrating. For example, having a layer for each strand of hair on an eyebrow will be a nightmare to keep track of and will make editing the whole eyebrow very difficult and time-consuming. Base Layer The first step I take when starting a texture is to create a base layer set below the wireframe layer. From this point, I make sure that in my Layers window the wireframe layer is always on top of the list and the base layer is always on the bottom of the list. All other layers will be placed in between. In general, my base layers usually start from a color, pattern, or image. Because most of what I m texturing in this map is skin, I fill the image with a base skin color. To do this, I set my Foreground Color to what I feel is a good skin color. I make sure the base layer is selected and press Alt+Backspace to fill my layer with the foreground color. To give the skin base some texture, I use a noise filter. I click Filter > Noise > Add Noise, then set the Amount to 3 and the Distribution to Uniform, making sure that Monochromatic is not selected. Figure 3 shows the results.

5 Creating Textures for Characters in Autodesk Maya 5 Figure 3. Base skin texture, with the UV snapshot on top of it Although the noise texture is subtle, it does become more apparent as I start painting shadows and highlights on the skin. Adding Detail to the Face For this step, it is useful to have a drawing tablet, such as a Wacom tablet and pen. Although it is possible to paint using a mouse, a tablet makes the job much easier and provides a nicer looking result.

6 6 Creating Textures for Characters in Autodesk Maya The first thing I m going to paint is the shadows and highlights on the face. I m not doing this with the brush tool but with the dodge tool, which allows me to pull the natural darks and lights out of the base texture that I ve created. This tool is ideal for keeping nice color saturation in the shadows and highlights. Because the dodge tool requires that I paint on the actual base layer, I make a duplicate of the base layer as a backup. If I make a mistake, I can use the back-up layer to cover up or fix the problem areas rather than having to start over. This is especially useful if I use an image or pattern for the base. Now, using my Wacom tablet and pen, I paint in some highlights. Then, holding down the Alt key, I paint the shadows. The dodge tool provides different range options: The Midtones option does a good job of maintaining color saturation in the highlights and shadows. Although I use this option most frequently, I also use the other two options Shadows and Highlights to provide additional detail and tone. Figure 4 shows a close-up of the face area, with all the shadows and highlights painted in. Figure 4. A close-up of the painted face area, with the wireframe layer on (left) and off (right) As I paint, I use the wireframe layer to make sure I m painting the highlights and shadows in the appropriate places. Turning the wireframe layer on and off helps me see how the texture is coming along. Next, I add the eyebrows, lips, and make-up. I create each element on its own layer so that I can edit each one individually. For the eyebrow and lips layers, I use the lasso tool and polygon lasso tool to draw selections for each shape. Next, I fill in the shape with a desired color. I then use the dodge tool to add highlights and shadows to each piece. To save time, I only create one eyebrow and mirror it over when I m done painting it. I do this by clicking Edit > Transform > Flip

7 Creating Textures for Characters in Autodesk Maya 7 Horizontal. This tip is also useful for any other areas that can be mirrored over from one side to the other. For the make-up layer, I paint detail on the cheeks and eyes. When painting make-up, I find that it s good practice to blend it into the face so that the color isn t too overbearing (unless that s the intention like a clown, for example). I do this by setting my brush tool to a low opacity, such as 5% or 10%. Then, I use as many strokes as I need to bring the color to the desired intensity. This works better than starting with a solid color and dialing it back. Figure 5 shows the addition of the eyebrows, lips, and make-up on the face. It s important to note that just because something looks good in Photoshop* doesn t mean it will look good when it is applied in Maya*. Figure 5. A close-up view of the finished face detail Saving Textures and Viewing Them in Maya As I m working on my texture map, I make sure that I save it so that I can apply it to the mesh in Maya* and see if it s working correctly. I save the image as TGA file, because that is the image format that I have worked with most for texture maps in video games. To apply the saved texture to the mesh in Maya*, I create a new material in the Multilister by clicking Edit > Create. I choose the desired material in this instance, a Lambert. In the Multilister, I double-click the new material, and the Attribute Editor appears. Next to the Color

8 8 Creating Textures for Characters in Autodesk Maya section, I click Map. In the Create Render Node window, beneath 2D Textures, I click File. The Attribute Editor brings up the attributes for the new file. Next to Image Name, I click the folder icon. From here, I can navigate to the folder where I saved my texture map and select it. Then, I select all of the meshes that I want the texture map applied to, select the material in the Multilister, and click Edit > Assign. Figure 6 shows the map assigned to the mesh pieces I selected. Figure 6. The fairy mesh in Maya* after the in-progress texture has been applied Anytime I save changes to the texture, I can update the changes in Maya* by double-clicking the texture in the Multilister, and then clicking Reload in the Attribute Editor. By checking the texture in Maya* regularly, I can make sure that I m painting it correctly. Then, I go back and forth between Photoshop* and Maya* until it s where it needs to be. Adding Remaining Detail Using the same techniques I ve already mentioned, I continue to add detail to the rest of the skin areas. For the ears, I use a photo. Then, I perform the following tasks:

9 Creating Textures for Characters in Autodesk Maya 9 1. Bring the photo into Photoshop*. 2. Use the lasso tool to select the ear. 3. Click Edit > Copy to copy the selection. 4. Go back to my texture, and then click Edit > Paste to paste the selection on to my texture, which will create its own layer. 5. Click Edit > Free Transform. A bounding box appears, and I can move, scale, and rotate the layer until it is in the desired position. 6. Use the eraser tool (with a feathered edge) to get rid of the areas of the ear that I don t want. 7. Click Image > Adjustments > Hue/Saturation. These controls allow me to adjust the different values so that the overall color of the ear matches the skin tone. I also use photos for the teeth and tongue. I paint the eyes, inner mouth, and outfit top. Figure 7 shows the finished texture and how it looks on the model.

10 10 Creating Textures for Characters in Autodesk Maya Figure 7. The mesh with the final texture applied, along with a screenshot of the actual texture, with the UV snapshot overlaid on it The whole time I m adding these extra details, I continue to go back and forth between Photoshop* and Maya* to make sure everything is working correctly. When I am finished with the map, I click Image > Image Size and take the pixel dimensions back down to

11 Creating Textures for Characters in Autodesk Maya 11 Conclusion Using similar techniques, I complete the additional texture map for the remaining mesh pieces that weren t included in the first map. Figure 8 shows a rendering of the fairy model, with the completed color textures. Figure 8. Rendering of the fairy model, with the final textures applied

12 12 Creating Textures for Characters in Autodesk Maya Getting everything to look just right can take some time. As a rule, when I finish an area, I step away for a bit. When I come back, I look to see if anything stands out that should be fixed. If there are areas that need to be tweaked, I take care of them. If I m happy with what I ve done, I move on. Use these techniques with your models, and good luck!