hi all,
I'm working with some bezier curves (ultimately, the goal is to benchmark
maya bifrost against regular maya - if you have any reference to share,
regarding bifrost perfs, feel free!).
I get my pos at parameter using directly matrices, no decasteljau involved,
I find it more elegant:
v_t = np.array([1, t, t**2, t**3])
cubic = np.array([
[ 1., 0., 0., 0.],
[-3., 3., 0., 0.],
[ 3., -6., 3., 0.],
[-1., 3., -3., 1.]
])
pos_at_param = np.dot(np.dot(v_t, cubic), control_points)
Works just fine. But I would like to compute my tangents using the same
logic
Whether I start from
(1-t)**3 +
3(1-t)**2t +
3(1-t)t**2 +
t**3
gets all those derivatives, and recreate a matrix out of it,
or start from the derivative I found online
3(1-t)(1-t) * (p1 - p0) +
6t(1-t) * (p2 - p1) +
3tt * (p3 - p2)
giving me
[ 3., 0., 0.]
[-6., 6., 0.]
[ 3., -5., 3.]
None of those seem to give me the actual derivative / tangent vector on my
curve at the given param. Am I doing something? Is it simply impossible to
compute the tangent of a curve using the same logic than the position?
Thank you
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