Like Interpolate(), but also return the index of the next polyline
vertex after the interpolated point P. This allows the caller to easily
construct a given suffix of the polyline by concatenating P with the
polyline vertices starting at "next_vertex". Note that P is guaranteed
to be different than vertex(*next_vertex), so this will never result in
a duplicate vertex.
The polyline must not be empty. Note that if "fraction" >= 1.0, then
"next_vertex" will be set to num_vertices() (indicating that no vertices
from the polyline need to be appended). The value of "next_vertex" is
always between 1 and num_vertices().
This method can also be used to construct a prefix of the polyline, by
taking the polyline vertices up to "next_vertex - 1" and appending the
returned point P if it is different from the last vertex (since in this
case there is no guarantee of distinctness).
Like Interpolate(), but also return the index of the next polyline vertex after the interpolated point P. This allows the caller to easily construct a given suffix of the polyline by concatenating P with the polyline vertices starting at "next_vertex". Note that P is guaranteed to be different than vertex(*next_vertex), so this will never result in a duplicate vertex.
The polyline must not be empty. Note that if "fraction" >= 1.0, then "next_vertex" will be set to num_vertices() (indicating that no vertices from the polyline need to be appended). The value of "next_vertex" is always between 1 and num_vertices().
This method can also be used to construct a prefix of the polyline, by taking the polyline vertices up to "next_vertex - 1" and appending the returned point P if it is different from the last vertex (since in this case there is no guarantee of distinctness).