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.
Street UVs
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 below images we see a street shape between a crossing (bottom) and roundabout (top). The left image illustrates the U values using shades of grey, 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 below 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 UVs
Intersection shapes that are street-like use the same UV set 0 parameterization as streets, without entries or exits. These shapes are Joint, Junction, Roudabout, 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
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.
