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

[Jerry Gray-Eskue]

A rather broad assumption considering that the only prerequisite for this
form is an interest in DIY Synths.
I am sure there are several people here that understood what you stated, but
I suspect that there are several more that are interested in your comments,
and if they were was a bit more verbose English explanation of your concepts
more of us would benefit from your expertise.




-----Original Message-----
From: cheater cheater [mailto:cheater00 at gmail.com]
Sent: Wednesday, March 24, 2010 2:22 PM
To: Jerry Gray-Eskue
Cc: synth-diy at dropmix.xs4all.nl
Subject: Re: [sdiy] Wave terrain synthesis (was Re: Generating
acyclicwaveforms?)


I assumed everyone here knew analytic geometry.

D.

On Wed, Mar 24, 2010 at 20:22, Jerry Gray-Eskue <jerryge at cableone.net>
wrote:
> 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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