UV coordinates are generated for each shape. They can be used for UV Splits and texturing. Up to three UV sets are supplied for each shape to describe different surface parameterizations.
There are three sets of UVs for street shapes.
Street UV Set 0
The first UV set provides a set of street lanes. The central region of the geometry is normalized along its length from 0 to 1, and across its width by 0 to the number of lanes. The number of lanes is specified by the street parameters. In the following images, you see a street shape between a crossing (bottom) and roundabout (top). The left image illustrates the U values using shades of gray, while the right image illustrates the V values.
The entry and exit of a street shape are parameterized to blend with the central region. For example, the entry (above, blue) and exit (green) u-values are oriented and scaled to match the central region (red). The entry has negative U values, and the exit has U values greater than 1.
Street UV Set 1 and 2
UV Sets 1 and 2 provide distance fields from the start of the entry and end of the exit, respectively. This information is provided in the U channel. The V channel is undefined. In the following image, the street direction is from the bottom to the top, and shows the orientation of UV Set 1 (left) and UV Set 2 (right).
Sidewalk shapes UV Set 0
The sidewalk shapes only provide a UV set 0. This is stitched to the street-side edge of the geometry; all street-adjacent edges have v-values of 0.
Intersection shapes that are street-like use the same UV set 0 parameterization as streets, without entries or exits. These shapes are Joint, Junction, Roundabout, Freeway, and FreewayEntry. In general, intersection shapes do not have other UV sets, with the exception of FreewayEntry. Similarly, intersection sidewalk shapes use the same UV set 0 parameterization as street sidewalk shapes.
The remaining shapes use a rectilinear projected UV set 0. These shapes are RoundaboutIsland and Crossing.
Freeway entries supply a UV set 1 to identify the inside edge shape that adjoins another street shape. The edge V = 0 is always on the inside of the freeway intersection.