Set the UV values of a vertex.
The UV values define the pixel location in a 0.0 to 1.0 coordinate system of the BitmapData.
Source
void setVertexUV(int vertex, num u, num v) {
var offset = vertex << 2;
vxList[offset + 2] = u.toDouble();
vxList[offset + 3] = v.toDouble();
}