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

cheater cheater cheater00 at gmail.com
Wed Mar 24 22:37:52 CET 2010 

On Wed, Mar 24, 2010 at 21:50, Walker Shurlds <walkershurlds at gmail.com> wrote:
> Didn't I explain the concept of "volts" to you just the other day?
>
> http://search.retrosynth.com/synth-diy/search/lookit.cgi?-v1001.337

You are flattering yourself. I've known the definition of voltage for
more than a decade now, and have known of the general usage for maybe
under two decades. Just because I asked a question doesn't mean I
didn't know (an) answer to it. Just because you typed out some form of
definition doesn't mean you enlightened me. It's a bit insulting that
you attribute something like this to yourself by the cost of
devaluating me. Don't mistake the act of syncing definitions to be 'on
the same page' (what I was doing) with paternal instruction (what you
implied happened). And even if you had instructed me on something, I
don't know what point you are trying to make with this. If it's an
attempt to get back at something, then know I'm not being derisive of
people who don't know calculus; all posts up to this one were
completely devoid of emotion, sorry if you took it otherwise.

> Honestly, I'd think it would be safer to assume that a poster here knows
> volts from amps before assuming they know calculus at all.

To understand the definition of voltage you brought up in that link
you need to understand the word 'average'. To understand this you need
to understand statistics, and in turn integrals, and in turn calculus,
and in turn linear algebra. If you don't, then your knowledge of
'volts' as you like to call the concept is shallow, and you benefit as
much from it as a cow chewing on grass benefits from botanics. That's
why I thought mathematics is likely to be known here, because it's a
basic ground for most of the knowledge being thrown about on this
list; that, and most EEs are forced through a year of calculus before
they're allowed anywhere near to an electronics book. For good reason,
it's very useful and gives you completely new ways to look at your
work.

Ian,
> Plus that, the notation is nonsensical.  The definition of C_1 is clear
> enough, but what on earth is C_{1,x}.  You certainly can't figure it out
> knowing C_1. This character is blowing smoke.

It's standard TeX notation for multiple subscripts and means "C with
subscript 1,x" which in turn signifies the x coordinate of the vector
"C with subscript 1". TeX and LaTeX notation for mathematics are
always used in ascii-based communication. You should know at least a
minimum about mathematical notation in technical papers, having
published those umpteens of scientific papers that you so like to
mention. If you did not understand mathematical notation, which mind
you DOES change from university to university, it's enough to ask,
instead of assuming the other end of the conversation is an idiot. But
I see for the last several days you have had a bad mood and post to
stir things up and generally put people down, I suggest chilling out a
little Ian.

D.

> On Wed, 24 Mar 2010 21:39:53 +0100
> cheater cheater <cheater00 at gmail.com> wrote:
>
>> On Wed, Mar 24, 2010 at 21:29, Jerry Gray-Eskue
>> <jerryge at cableone.net> wrote:
>> > 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.
>>
>> I guess you're right. I can only invite everyone who reads this to
>> pick up and read an introductory linear algebra/calculus book for
>> technical university students that covers complex and linear algebra,
>> discrete mathematics, classical calculus and multivariate calculus.
>> This is infinitely useful in understanding sound synthesis, be it
>> analog or digital.
>>
>> Unfortunately the mathematics above can't be explained to the layman
>> in less than ten paragraphs at which point it becomes pointless, but
>> if you read the first paragraphs of definition for these terms you
>> should be able to understand everything:
>>
>> - parametrized curve
>> - vector perpendicular to a curve
>> - vector parallel to a curve
>> - derivative of a vector
>>
>> Cheers
>> D.
>>
>> P.S. in the previous post I should have said 'phase' not 'phasor' of
>> course :-)
>>
>>
>> >
>> >
>> >
>> >
>> > -----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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