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/* TRANS(A, ALPHA, B, N, OUTPUT) makes a transition from A to B in N steps
according to transition parameter ALPHA. It stores the resulting N values
starting at location OUTPUT. ALPHA = 0 will yield a straight line;
ALPHA < 0 will yield an exponential transition, ALPHA > 0 will yield
a logarithmic transition, according to the formula:
OUTPUT[i] = A + (B - A) * (1 - exp( i*alpha/(n-1) )) / (1 - exp(alpha))
for 0 <= i < n .
*/
#include <stdio.h>
#include <math.h>
trans(a, alpha, b, n, output)
float a, alpha, b, *output; int n;
{
register int i;
register float d, e;
register float interval;
register float delta = b - a;
if(n > 1) interval = 1./(n - 1.);
else {fprintf(stderr, "trans: transition length <= 1\n"); exit(-1);}
if(alpha != 0.0){
register float denom;
denom = 1./(1. - exp( (double) alpha));
for(i=0; i<n; i++)
*output++ = a + delta*(1. - exp( (double) i*alpha*interval))*denom;
} else
for(i=0; i<n; i++) *output++ = a + delta*i*interval;
}
These are the contents of the former NiCE NeXT User Group NeXTSTEP/OpenStep software archive, currently hosted by Netfuture.ch.