Viewing UVs in the UV Editor

The UV Editor lets you view and interactively edit the UV texture coordinates for polygon and subdivision surface types. UVs appear laid flat within the UV Editor’s 2D view. It also lets you display the 2D image for the texture map in relation to the UVs. These features are critical for accurate and efficient placement of texture maps on polygon and subdivision surface types.

In this lesson, your goal is to ensure that the shape and placement of the UVs match the image as it appears in the 2D view of the UV Editor. This will ensure that the map appears correctly on the cracker box model in the 3D scene view.

To open the UV Editor

1. In the Modeling menu, select UV > UV Editor.

   

   The UV Editor opens in another window. You can drag the window over one of the viewport borders to change Maya's layout to a two-pane, with perspective view and the UV Editor. Being able to see both the UV Editor and your model is important because:

   • It shows you how one item selected in the 3D view relates to the UVs displayed in the 2D view of the UV Editor and vice versa, without having to open and close the views repeatedly.
   • When you edit UVs for a surface mesh in the UV Editor, you can immediately see the effect of the texture map on the model in the 3D scene view.

UVs do not initially appear in the 2D view of the UV Editor until you select an object or change the selection mode for an object in the scene view.

To view UVs in the UV Editor

1. In the scene view, right-click any region of the cracker box model and select Object Mode from the marking menu.
2. Select the cracker box model.
3. In the UV Editor, dolly the view outwards so you can see the UVs for the cracker box as shown below. (To dolly, press the Alt key and drag the mouse to the left while holding down the right button on your mouse.)

   The UV texture coordinates for the cracker box model appear in the 2D view of the UV Editor as a flattened, two-dimensional representation. The UVs appear highlighted with lines connecting the UVs to indicate the region of the texture the UVs represent.

   The image you specified as the texture map for the box also appears in the 2D view of the UV Editor in the upper right quadrant of the 2D cartesian graph called the UV image range or UV Texture Space. The coordinates for this quadrant range from 0,0 to 1,1 and represent the texture space for the surface. How the UVs appear in this quadrant in relation to the displayed image has a direct bearing on how the texture gets mapped onto the surface.

   Tip:

   If the texture map for the cracker box doesn’t appear in the 2D view, select Image > Update PSD Networks in the UV Editor to refresh the 2D view of the UV Editor. Update PSD Network is normally used to refresh a PSD texture in Maya after you have modified the PSD texture in Adobe® Photoshop®.

   

   In this example, the UVs for the cracker box appear like a box where all six sides have been cut open and then unfolded flat.

   The texture map does not appear correctly on the cracker box for a number of reasons:

   • The UVs for the cracker box extend well beyond the default 0 to 1 UV range for the texture map in the 2D view of the UV Editor. As the texture map displays within the 0 to 1 range, the UVs should also be positioned to fit within the 0 to 1 UV range, in most cases. Otherwise, the texture map repeats on the surface mesh, as it does in this case.
   • The position of the UVs do not match the specific regions of the image we’ve provided for the texture map. The regions of the image show the front, back, top, bottom, and sides of the box. The UVs should specifically match these regions to display the texture correctly. UVs do not automatically align themselves to a texture, you must manually reposition them.
   • The shape of the UVs don’t match the aspect ratio of the cracker box model in the scene view: 10 (Height) X 8 (Width) X 3 (Depth). This is because the default UVs for a Maya cube primitive are created based on a predetermined default shape and do not get updated if the shape or scale of the primitive is modified later on.

There are a number of things you can do to correct these issues depending on the situation. For this lesson, you will correct the UV and texture map misalignment by doing the following:

• Map a new set of UVs for the cracker box model that better matches the individual faces of the cracker box. (While the existing UVs could be modified, you’ll learn how to create new UVs in this lesson that will better match the size and scale of the 3D model.)
• Ensure the new UVs fit within the 0 to 1 UV range in the UV Editor.
• Reposition the UVs so that they correlate to specific locations on the 2D image using the UV Editor. This will ensure that the various sides of the box receive the correct regions of the texture map.