[Bf-docboard] sine wave errata

[Randall Rickert]

In the user documentation on this page:
http://download.blender.org/documentation/htmlI/ch21s03.html

It says:
> To obtain a Sinusoidal-like wave
>
> To obtain a nice Wave effect similar to sea waves and close to a  
> sinusoidal wave it is necessary that the distance between following  
> ripples and the ripple width are equal, that is the Width Num  
> Button value must be equal to 4 over the Narrow value.
There is a nice diagram also. Both the diagram and the text are  
incorrect. The formula Width=4/Narrow does not create something like  
a sine wave. This is easy to see if you try using the values Width=4  
and Narrow=1. The result does not look at all like a sine wave.

As far as I can tell, the formula for a wave that looks sinusoidal  
should be Width=Pi/(2*Narrow). Probably a better way to write it is  
Narrow=Pi/(2*Width), because most people would probably start with a  
wavelength in mind (the wavelength is Width*2).

It's a bad interface anyway, because making a sine wave (probably the  
most common wave the user will want to make) shouldn't require the  
user to calculate Pi/(2*whatever).

-Randall