1 | function stiffnessFromOrigamiValue(oValue) {
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2 | return (oValue - 30) * 3.62 + 194;
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3 | }
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4 |
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5 | function dampingFromOrigamiValue(oValue) {
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6 | return (oValue - 8) * 3 + 25;
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7 | }
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8 |
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9 | function fromOrigamiTensionAndFriction(tension, friction) {
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10 | return {
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11 | stiffness: stiffnessFromOrigamiValue(tension),
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12 | damping: dampingFromOrigamiValue(friction),
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13 | };
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14 | }
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15 |
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16 | function fromBouncinessAndSpeed(bounciness, speed) {
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17 | function normalize(value, startValue, endValue) {
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18 | return (value - startValue) / (endValue - startValue);
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19 | }
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20 |
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21 | function projectNormal(n, start, end) {
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22 | return start + n * (end - start);
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23 | }
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24 |
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25 | function linearInterpolation(t, start, end) {
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26 | return t * end + (1 - t) * start;
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27 | }
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28 |
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29 | function quadraticOutInterpolation(t, start, end) {
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30 | return linearInterpolation(2 * t - t * t, start, end);
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31 | }
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32 |
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33 | function b3Friction1(x) {
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34 | return 0.0007 * Math.pow(x, 3) - 0.031 * Math.pow(x, 2) + 0.64 * x + 1.28;
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35 | }
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36 |
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37 | function b3Friction2(x) {
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38 | return 0.000044 * Math.pow(x, 3) - 0.006 * Math.pow(x, 2) + 0.36 * x + 2;
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39 | }
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40 |
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41 | function b3Friction3(x) {
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42 | return (
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43 | 0.00000045 * Math.pow(x, 3) -
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44 | 0.000332 * Math.pow(x, 2) +
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45 | 0.1078 * x +
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46 | 5.84
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47 | );
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48 | }
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49 |
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50 | function b3Nobounce(tension) {
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51 | if (tension <= 18) {
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52 | return b3Friction1(tension);
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53 | } else if (tension > 18 && tension <= 44) {
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54 | return b3Friction2(tension);
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55 | } else {
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56 | return b3Friction3(tension);
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57 | }
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58 | }
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59 |
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60 | var b = normalize(bounciness / 1.7, 0, 20);
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61 | b = projectNormal(b, 0, 0.8);
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62 | var s = normalize(speed / 1.7, 0, 20);
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63 | var bouncyTension = projectNormal(s, 0.5, 200);
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64 | var bouncyFriction = quadraticOutInterpolation(
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65 | b,
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66 | b3Nobounce(bouncyTension),
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67 | 0.01
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68 | );
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69 |
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70 | return {
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71 | stiffness: stiffnessFromOrigamiValue(bouncyTension),
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72 | damping: dampingFromOrigamiValue(bouncyFriction),
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73 | };
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74 | }
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75 |
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76 | module.exports = {
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77 | fromOrigamiTensionAndFriction,
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78 | fromBouncinessAndSpeed,
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79 | };
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