[sdiy] Wave terrain synthesis (was Re: Generating acyclicwaveforms?)

[Jerry Gray-Eskue]

And a little subspace distortion....;)

-----Original Message-----
From: synth-diy-bounces at dropmix.xs4all.nl
[mailto:synth-diy-bounces at dropmix.xs4all.nl]On Behalf Of Tom Wiltshire
Sent: Wednesday, March 24, 2010 1:45 PM
To: cheater cheater
Cc: synth-diy at dropmix.xs4all.nl
Subject: Re: [sdiy] Wave terrain synthesis (was Re: Generating
acyclicwaveforms?)


Hehe, you *must* be making that up! Just add more dilithium crystals!

T.

On 24 Mar 2010, at 18:32, cheater cheater wrote:

> Actually it's some sort of generalization of both at the same time.
>
> If you have a trajectory C_1(phi) : [0, 1] -> R^2 over which the
> terrain is scanned then translating it by a vector by doing C_2(phi) =
> (C_{1,x}(phi) + L_x, C_{2,x}(phi) + L_y) (where L is a certain vector
> and (x,y) signifies a vector in R^2) will work just like a wavetable
> index scan in the part of the trajectory that is perpendicular to the
> vector L, and will work like pitch bending in the part of the
> trajectory that is parallel to the vector if dL/dt is a non-zero
> constant.
>
> Changing the function C_1(phi) or the phasor function from phi(x) = x
> to something different will work like PM.
>
> D.
>
> On Wed, Mar 24, 2010 at 11:23, Tom Wiltshire  
> <tom at electricdruid.net> wrote:
>> I find it very interesting that this technique makes similar  
>> sounds to FM,
>> since in my mind it is more closely related to wavetable synthesis  
>> than
>> either of the nonlinear techniques you mention (waveshaping and  
>> FM). I can
>> completely imagine that it is difficult to control or predict what  
>> you'll
>> get out. Experimentation is good, but sometimes you're aiming for  
>> something
>> particular and it would be nice to be able to get closer.
>>
>> Thanks very much for a practical report on this.
>>
>> T.
>>
>> On 24 Mar 2010, at 03:46, Scott Nordlund wrote:
>>
>>>
>>>> Simon Brouwer wrote:
>>>>>
>>>>> I see two other ways:
>>>>> - using wavetables (very long ones)
>>>>
>>>> I'd discounted wavetables just because they would have to be  
>>>> very long,
>>>> but memory is cheap, so why not.
>>>>
>>>> What about Wave Terrain synthesis? Is there an sdiy implementation
>>>> anywhere? Load up a 2-d matrix with a surface of choice and then  
>>>> read
>>>> linear subsections. Altering the start and end coordinates over  
>>>> time to
>>>> vary the output waveform.
>>>>
>>>> -Dave
>>>
>>> I've tried wave terrain synthesis in Pure Data.  It's neat to  
>>> think about,
>>> but the results I've gotten aren't drastically different from FM or
>>> waveshaping or similar things (you could kind of consider  
>>> waveshaping and
>>> FM to be subsets of wave terrain).  My implementation scanned a  
>>> surface
>>> (defined by an arbitrary equation, F(x,y)) with a sort of  
>>> lissajous figure
>>> that could be scaled, rotated, offset, etc.  To get something decent
>>> sounding, I limited the surface and modulation to continuous,  
>>> bounded
>>> functions (lots of sin, cos, atan).  A surface with  
>>> discontinuities or
>>> singularities isn't going to sound so great.
>>>
>>> Anyway, yes, there's plenty of room for inharmonics and animated and
>>> complex sounding things, and it's nice that any of the inputs can  
>>> be used
>>> with envelopes or slow or fast modulation or whatever, but  
>>> there's also
>>> a lot of unintuitive messing about to avoid sudden and  
>>> "unmusical" timbral
>>> changes, or just to generally come up with something interesting.
>>>
>>> The end result resembles something that might be more easily  
>>> obtained from
>>> FM/waveshaping with arbitrary waveforms.  In fact that might be a  
>>> better
>>> approach, because it's difficult to make an equation for an  
>>> interesting
>>> surface.
>>>
>>> I'm not saying it's not interesting or potentially rewarding, but  
>>> it's not
>>> the revelation that I'd hoped for.  Imagine FM with several added  
>>> layers
>>> of confusion and obfuscation and you won't be too far off.
>>>
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