smoothNormalLinear
Evaluates a normal at rectified t such that it is linearly blended with the normal of the neighbouring segment when t lies within radius (in arc length) of a corner formed by a segment join.
When t falls exactly on a corner the returned normal is the average of the normals of the two segments. The effective radius around a corner is limited to half the length of each of the two adjacent segments, such that blend regions of neighbouring corners never overlap.
Parameters
t
rectified t-value
radius
blend radius in arc length