parameters p0, p1, t0, t1

[burrGee]

It is not clear to me what the vectors p0, p1, t0, and t1 represent.

[dsforza96]

If I remember correctly, they should be the four control points of the bézier curve defining the contour of the tree's crown, starting from the end of the trunk (p0) to the top of the crown (p1). See https://en.wikipedia.org/wiki/B%C3%A9zier_curve, where p0 -> P0, t0 -> P1, p1 -> P3, t1 -> P2.