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Some more solveCubic() work

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Should be stable again now.
This commit is contained in:
Behdad Esfahbod 2016-06-08 18:56:31 -07:00
parent 93d08d4188
commit 78c29bc5a1
1 changed files with 7 additions and 3 deletions
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10
Lib/fontTools/misc/bezierTools.py
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@ -319,13 +319,17 @@ def solveCubic(a, b, c, d):
Q = (a1*a1 - 3.0*a2)/9.0
R = (2.0*a1*a1*a1 - 9.0*a1*a2 + 27.0*a3)/54.0
R = 0 if abs(R) < epsilon else R
Q = 0 if abs(Q) < epsilon else Q
R2_Q3 = R*R - Q*Q*Q
if abs(R) < epsilon and abs(Q) < epsilon:
if R == 0. and Q == 0.:
x = -a1/3.0
return [x, x, x]
elif R2_Q3 < epsilon:
theta = acos(min(R/sqrt(Q*Q*Q), 1.0))
elif R2_Q3 <= epsilon:
theta = acos(max(min(R/sqrt(Q*Q*Q), 1.0), -1.0))
rQ2 = -2.0*sqrt(Q)
a1_3 = a1/3.0
x0 = rQ2*cos(theta/3.0) - a1_3