by Johan Borgström
To render a UV pass from Maya using V-Ray simply create a samplerInfo node and connect the uCoord to the vray extra texture Red channel and vCoord to the Green channel.
Render and your done.
Make sure that you render in 32 bit and make sure that when imported into your composition app no color adjustments are applied to the image.


To understand how a UV map is constructed it is helpful to think of the UV map as information of position in X and Y. The UV map consists of two colors, red and green. The U element is mapped from 0 to 1 in the red channel. Starting on the left side t with 0 to 1 on the right side.

The V element is contained in the G green channel starting with 0 at the bottom ranging to 1 at the top.

When combined the UV map looks like this and is able to give unique position on a 2d plane with values ranging from 0 to 1 in both the x and y dimensions.