UV Mapping

A UV map is a pass which records the way the pixels of an image should be displaced within the image plane, so that the warped texture looks like the textured geometry from the point of view of the CG camera. The UV map acts as a 2D distortion field, or a pixel look up table, recording where every pixel of an input image texture should be, had it been applied on a geometry filmed by the CG camera. It is a very effective way of faking 3D mappings, without having a single polygon. It is most effective when combined with a Normal map, which can be used to simulate the shading of the actual geometry even though everything is perfectly flat.

Applying a UV map to surface or geometry, warps its texture according to the defined UV. The U information is coded in the Red channel, while the V information is coded in the Green channel of the UV map image. For each pixel of the UV map, the red or green value corresponds to a given pixel on the unwrapped texture, and it is this pixel that gets displaced at the position of the same pixel in the attached surface or geometry.

Here are a few things to keep in mind when working with UV maps:

• To avoid pixelation in your imported UV passes, make sure that the UV pass is rendered as a 16-bit floating point image from your 3D application.
• It is a good idea to render UV passes without anti-aliasing to avoid warping on the edges of objects that the UV map is applied to. Since you can also output a UV Map from Flame, make sure that anti-aliasing is not selected in the Render Options section of the Output menu.
• You can embed object IDs in the Blue channel when performing a UV render pass in Maya, allowing you to specify which objects are displaced within the UV map in Action. In Maya, when performing a UV Render Pass, enable Embed Object ID in Blue Channel. When disabled, blue channel information is ignored.
• For best results, in the Texture settings of the UV Map menu in Flame, the Fit Method box should be set to Fill, and the Filter box to Nearest.

Flat texture

UV Map

Texture with UV Map applied

To add a UV map:

1. In the schematic, select the surface or 3D geometry to which you want to apply the UV map.
2. Click Media.
3. In the Media menu, select the media you want to use for the UV map.
4. Do one of the following:
   • Drag the UV Map node from the node bin and place it in the schematic.
   • Drag the UV Map node from the node bin and place it where you want it in Result view.
   • Double-click the UV Map node. You do not need to be in Schematic view to add a node in this manner.

   The UV object is added to the schematic with its own parent axis. The new axis is the child of the selected surface or geometry. In Schematic view, the number in brackets next to the name of the UV node indicates the media used for the UV.

   

   To specify different media as the UV source, select the media in the Media menu, then click Apply.

5. Double-click the UV node in the Schematic view, or follow the tab population rules for the Object menu.

   The UV menu appears.