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{ RCSid $Id: spline.cal,v 1.2 2018/11/21 18:10:45 greg Exp $ } |
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{ |
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Calculation of view parameters for walk-throughs. |
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Uses Catmull-Rom spline. |
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|
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09Feb90 Greg Ward |
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|
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Define: |
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T(i) - time between keyframe i and i-1 |
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Input: |
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t - time |
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Output: |
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s(f) - spline value for f at t where f(i) is value at T(i) |
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} |
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or(a,b) : if(a, a, b); |
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hermite(p0,p1,r0,r1,t) : p0 * ((2*t-3)*t*t+1) + |
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p1 * (-2*t+3)*t*t + |
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r0 * (((t-2)*t+1)*t) + |
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r1 * ((t-1)*t*t); |
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Ttot : sum(T,T(0)); |
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sum(f,n) : if(n-.5, f(n)+sum(f,n-1), 0); |
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tfrac = (t-sum(T,below))/T(above); |
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upper(s,i) = if(or(i-T(0)+.5,s+T(i)-t), i, upper(s+T(i),i+1)); |
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below = above-1; |
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above = max(upper(0,1),2); |
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below2 = max(below-1,1); |
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above2 = min(above+1,T(0)); |
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s(f) = hermite(f(below), f(above), |
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(f(above)-f(below2))/2, (f(above2)-f(below))/2, |
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tfrac); |
