Exponential curve for

Type : Exponential curve
References : Posted by neolit123 [at] gmail [dot] com
Notes :
When you design a frequency control for your filters you may need an exponential curve to give the lower frequencies more resolution.

F=20-20000hz
x=0-100%

Case (control middle point):
x=50%
F=1135hz

Ploted diagram with 5 points:
http://img151.imageshack.us/img151/9938/expplotur3.jpg

Code :
//tweak - 14.15005 to change middle point and F(max)
F = 19+floor(pow(4,x/14.15005))+x*20;


Comments
from : neolit123[AT]gmail[DOT]com
comment : Yet another one! :) This is one should be the most linear one out of the 3. The 50% appears to be exactly the same as Voxengo span midpoint. //x - 0-100% //y - 20-20k y = floor(exp((16+x*1.20103)*log(1.059))*8.17742); //x=0, y=20 //x=50, y=639 //x=100, y=20000

from : neolit123[AT]gmail[DOT]com
comment : Here is another function: This one is much more expensive but should sound more linear. //t - offset //x - 0-100% //y - 20-20000hz t = 64.925; y = floor(exp(x*log(1.059))*t - t/1.45); Comparison between the two: [IMG]http://img528.imageshack.us/img528/641/plot1nu1.jpg[/IMG]

from : neolit123[AT]gmail[DOT]com
comment : same function with the more friendly exp(x) y = 19+floor(exp(x/10.2071))+x*20; middle point (x=50) is still at 1135hz