Creating and Displaying a UV Test Grid
At this point, you could start unwrapping, but instead you’re going to create a UV Test Grid so you can see how applying a texture to the face will look before unwrapping. With the test grid, you’ll see how an image is projected on the 3D model using the UVs more easily.
A UV Test Grid is a basic image made exclusively to test how the UVs of a mesh work. It’s an image with a grid; when it’s projected on the 3D model, it provides you with a lot of information. The size of the grid will show you which parts of your object are using more space from the texture (the smaller the grid, the more resolution the texture will have in that area). Using the test grid, you can adjust the size of every part of the object to be more or less consistent, and you can apply a smaller grid to those parts where you need more details. It’s also useful to see the grid’s distortion; if you notice that at some point the grid is becoming distorted, you can try to solve this by adjusting the UVs. Using a UV Test Grid, you can also see where the seams are and how well they work, or if they’re barely visible.
The UV Test Grid can also have colors as well as letters or numbers. This will tell you which part of the UVs is being shown in a specific part of the model by the color, number, or letter it displays on its surface.
Creating a New Image for a UV Test Grid
Fortunately, Blender has two different types of UV Test Grids that you can generate and use in your models. To create them, just go to the UV/Image Editor header and click New Image. You can also go to the Image menu and click New Image or use the keyboard shortcut: Alt + N.
In Figure 8.6, you can see the New Image menu that pops up, where you can create images to paint on or UV Test Grids. You can set the image’s name (Untitled by default), its resolution, and its color. The color will only apply when you select Blank as the Generated Type of image. If you select one of the UV Test Grids as the Generated Type, the color setting will be ignored.
Figure 8.6 Generating a new image in Blender, with the New Image menu (left), a UV grid (center), and a Color grid (right)
Once you’ve made your selections, click OK to generate the image. You can change the image’s name from the header and save it from the Image menu. If you open the Properties Region (N), in the Image panel you can also rename the image and access its parameters. Because the image is generated by Blender, you can change its type even after it is created, and also change between a UV grid or a color grid (or a blank image, or course).
Displaying the UV Test Grid in Your Model
How you show the image you’re using in a 3D model in the 3D View depends on which render engine you’re using. Let’s see how to display an image in both Blender Render and Cycles.
Both render engines let you display a texture by applying it to a material and switching the display mode of the 3D View to Textured. But with Blender Render, there is another method that doesn’t require you to create a material, but you need to have UVs in your mesh in order to use it.
Go to the UV/Image Editor and load the image while the UVs are displayed. This is called a Texture Face, the texture that is “applied” to a UV Map. Now, in the 3D View, you can display that Texture Face even in the Solid display mode; open the Properties Region (N), and in the Shading panel, activate the Textured Solid option.
In Cycles, there is a better way to do this that uses a material. Create a new material from the Material tab in the Properties Editor and call it something like “uv_test_mat”; this way, you’ll always have a UV Test material in your scene ready to be applied to the object with which you’re working. Inside the Material options, in the Color parameter, click the button with a little dot at the right of the color selector and select Image Texture from the list. From the drop-down list, select the UV Test Grid you’ve just created. Now go to the 3D View and use the Textured or Material display modes to see how the UV Test Grid looks.