[Bf-docboard] Re: sine wave errata

[Randall Rickert]

Sorry, looking at it closer, the documentation says:

> The actual width of the area in which the single pulse is  
> significantly non-zero in Blender Units is given by 4 over the  
> Narrow Value. That is, if Narrow is 1 the pulse is 4 Units wide,  
> and if Narrow is 4 the pulse is 1 Unit Wide.

It seems this formula should be 4 over twice the Narrow value i.e.: 4/ 
(2*Narrow), not 4/Narrow. I tried different values to get closer to a  
sine wave, such as Pi/(2*Narrow). It's really not possible to make a  
sine wave in Blender, because the pulse is a Gaussian function or  
such, not a sine function. 4/(2*Narrow) makes the wave very smooth,  
but the peaks are a bit more narrow than the valleys.

My suggestion of Pi/(2*Narrow) looked more like a sine wave, but it  
makes a subtle crease in the valley. 4/(2*Narrow) is a better  
formula, and is probably the formula the original author intended  
when they wrote "4 over Narrow".

-Randall


> Date: Mon, 17 Oct 2005 03:27:55 -0700
> From: Randall Rickert <randall at rickert-digital.com>
> Subject: [Bf-docboard] sine wave errata
> To: bf-docboard at projects.blender.org
> Message-ID: <8E36C3EA-5636-493F-BA71-51DBFD628C43 at rickert-digital.com>
> Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed
>
> 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

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