I got confused by the way to calculate the interpolated point and t for a second so just including this for clarity. While t represents the distance away from the anchor point (the ratio between the distance to the anchor to the total length of the substance), to calculate the actual coordinate of the interpolated point the weight attached to the anchor is 1 - t and to the end point is t (so everything this flipped) when we are calculating the actual coordinates of the point vs when we are describing the position of the point relative to the length of the segment.
I got confused by the way to calculate the interpolated point and t for a second so just including this for clarity. While t represents the distance away from the anchor point (the ratio between the distance to the anchor to the total length of the substance), to calculate the actual coordinate of the interpolated point the weight attached to the anchor is 1 - t and to the end point is t (so everything this flipped) when we are calculating the actual coordinates of the point vs when we are describing the position of the point relative to the length of the segment.