1 | var rho = Math.SQRT2,
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2 | rho2 = 2,
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3 | rho4 = 4,
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4 | epsilon2 = 1e-12;
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5 |
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6 | function cosh(x) {
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7 | return ((x = Math.exp(x)) + 1 / x) / 2;
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8 | }
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9 |
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10 | function sinh(x) {
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11 | return ((x = Math.exp(x)) - 1 / x) / 2;
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12 | }
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13 |
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14 | function tanh(x) {
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15 | return ((x = Math.exp(2 * x)) - 1) / (x + 1);
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16 | }
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17 |
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18 |
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19 |
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20 | export default function(p0, p1) {
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21 | var ux0 = p0[0], uy0 = p0[1], w0 = p0[2],
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22 | ux1 = p1[0], uy1 = p1[1], w1 = p1[2],
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23 | dx = ux1 - ux0,
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24 | dy = uy1 - uy0,
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25 | d2 = dx * dx + dy * dy,
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26 | i,
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27 | S;
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28 |
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29 |
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30 | if (d2 < epsilon2) {
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31 | S = Math.log(w1 / w0) / rho;
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32 | i = function(t) {
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33 | return [
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34 | ux0 + t * dx,
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35 | uy0 + t * dy,
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36 | w0 * Math.exp(rho * t * S)
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37 | ];
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38 | }
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39 | }
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40 |
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41 |
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42 | else {
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43 | var d1 = Math.sqrt(d2),
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44 | b0 = (w1 * w1 - w0 * w0 + rho4 * d2) / (2 * w0 * rho2 * d1),
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45 | b1 = (w1 * w1 - w0 * w0 - rho4 * d2) / (2 * w1 * rho2 * d1),
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46 | r0 = Math.log(Math.sqrt(b0 * b0 + 1) - b0),
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47 | r1 = Math.log(Math.sqrt(b1 * b1 + 1) - b1);
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48 | S = (r1 - r0) / rho;
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49 | i = function(t) {
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50 | var s = t * S,
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51 | coshr0 = cosh(r0),
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52 | u = w0 / (rho2 * d1) * (coshr0 * tanh(rho * s + r0) - sinh(r0));
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53 | return [
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54 | ux0 + u * dx,
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55 | uy0 + u * dy,
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56 | w0 * coshr0 / cosh(rho * s + r0)
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57 | ];
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58 | }
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59 | }
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60 |
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61 | i.duration = S * 1000;
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62 |
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63 | return i;
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64 | }
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