1 files changed, 140 insertions, 0 deletions
diff --git a/third_party/spiro/curves/cornu.py b/third_party/spiro/curves/cornu.py
new file mode 100644
index 0000000..26f68e9
--- /dev/null
+++ b/third_party/spiro/curves/cornu.py
@@ -0,0 +1,140 @@
+from math import *
+
+# implementation adapted from cephes
+
+def polevl(x, coef):
+    ans = coef[-1]
+    for i in range(len(coef) - 2, -1, -1):
+        ans = ans * x + coef[i]
+    return ans
+
+sn = [
+-2.99181919401019853726E3,
+ 7.08840045257738576863E5,
+-6.29741486205862506537E7,
+ 2.54890880573376359104E9,
+-4.42979518059697779103E10,
+ 3.18016297876567817986E11
+]
+sn.reverse()
+sd = [
+ 1.00000000000000000000E0,
+ 2.81376268889994315696E2,
+ 4.55847810806532581675E4,
+ 5.17343888770096400730E6,
+ 4.19320245898111231129E8,
+ 2.24411795645340920940E10,
+ 6.07366389490084639049E11
+]
+sd.reverse()
+cn = [
+-4.98843114573573548651E-8,
+ 9.50428062829859605134E-6,
+-6.45191435683965050962E-4,
+ 1.88843319396703850064E-2,
+-2.05525900955013891793E-1,
+ 9.99999999999999998822E-1
+]
+cn.reverse()
+cd = [
+ 3.99982968972495980367E-12,
+ 9.15439215774657478799E-10,
+ 1.25001862479598821474E-7,
+ 1.22262789024179030997E-5,
+ 8.68029542941784300606E-4,
+ 4.12142090722199792936E-2,
+ 1.00000000000000000118E0
+]
+cd.reverse()
+
+fn = [
+  4.21543555043677546506E-1,
+  1.43407919780758885261E-1,
+  1.15220955073585758835E-2,
+  3.45017939782574027900E-4,
+  4.63613749287867322088E-6,
+  3.05568983790257605827E-8,
+  1.02304514164907233465E-10,
+  1.72010743268161828879E-13,
+  1.34283276233062758925E-16,
+  3.76329711269987889006E-20
+]
+fn.reverse()
+fd = [
+  1.00000000000000000000E0,
+  7.51586398353378947175E-1,
+  1.16888925859191382142E-1,
+  6.44051526508858611005E-3,
+  1.55934409164153020873E-4,
+  1.84627567348930545870E-6,
+  1.12699224763999035261E-8,
+  3.60140029589371370404E-11,
+  5.88754533621578410010E-14,
+  4.52001434074129701496E-17,
+  1.25443237090011264384E-20
+]
+fd.reverse()
+gn = [
+  5.04442073643383265887E-1,
+  1.97102833525523411709E-1,
+  1.87648584092575249293E-2,
+  6.84079380915393090172E-4,
+  1.15138826111884280931E-5,
+  9.82852443688422223854E-8,
+  4.45344415861750144738E-10,
+  1.08268041139020870318E-12,
+  1.37555460633261799868E-15,
+  8.36354435630677421531E-19,
+  1.86958710162783235106E-22
+]
+gn.reverse()
+gd = [
+  1.00000000000000000000E0,
+  1.47495759925128324529E0,
+  3.37748989120019970451E-1,
+  2.53603741420338795122E-2,
+  8.14679107184306179049E-4,
+  1.27545075667729118702E-5,
+  1.04314589657571990585E-7,
+  4.60680728146520428211E-10,
+  1.10273215066240270757E-12,
+  1.38796531259578871258E-15,
+  8.39158816283118707363E-19,
+  1.86958710162783236342E-22
+]
+gd.reverse()
+
+
+def fresnel(xxa):
+    x = abs(xxa)
+    x2 = x * x
+    if x2 < 2.5625:
+        t = x2 * x2
+        ss = x * x2 * polevl(t, sn) / polevl(t, sd)
+        cc = x * polevl(t, cn) / polevl(t, cd)
+    elif x > 36974.0:
+        ss = 0.5
+        cc = 0.5
+    else:
+        t = pi * x2
+        u = 1.0 / (t * t)
+        t = 1.0 / t
+        f = 1.0 - u * polevl(u, fn) / polevl(u, fd)
+        g = t * polevl(u, gn) / polevl(u, gd)
+        t = pi * .5 * x2
+        c = cos(t)
+        s = sin(t)
+        t = pi * x
+        cc = 0.5 + (f * s - g * c) / t
+        ss = 0.5 - (f * c + g * s) / t
+    if xxa < 0:
+        cc = -cc
+        ss = -ss
+    return ss, cc
+
+def eval_cornu(t):
+    spio2 = sqrt(pi * .5)
+    s, c = fresnel(t / spio2)
+    s *= spio2
+    c *= spio2
+    return s, c