I'm stuck with developing algorithm to trim b-spline so it begins at certain point without changing it's shape. I'm using these formulas: link. I have already implemented inserting knot at given t. Let me show you example of what I'm trying to do.
Control points of my spline are: ((0, 0), (19, 0), (0, 12), (28, 38), (56, 14), (34, 0), (56, 0))
Knot vector of original spline is: (0, 0, 0, 0, 0,25, 0,5, 0,75, 1, 1, 1, 1)
Degree of spline: 3.
Now I would like add a knot at let's say 0.3 and then cut all that preceeds 0.3 without changing the shape of curve so it starts at inserted point.