[PD] get sinusoid from a sine and a cosine oscillator
Alexandros Drymonitis
adrcki at gmail.com
Thu Jan 30 17:17:48 CET 2014
In the case of the circle I could just use one of the tables, since one has
the cosine and the other the sine, and output that as an oscillator, but if
I want to combine functions to create shapes, e.g. one function for the x
axis and another for y, how can I combine these two dimensions in one?
I don't really get what you mean by (x,y)->x or (x,y)->y, or the equation
you wrote (tried it but didn't sound as expected, maybe my implementation
was wrong).
On Thu, Jan 30, 2014 at 6:06 PM, Charles Z Henry <czhenry at gmail.com> wrote:
> You don't want fft~/ rifft~ for that. It's a mapping between large
> structures on blocks and single-samples (and vice-versa).
>
> To get a single sinusoid from a path-defined circle, you just project onto
> a single dimension. For example, (x,y)->x or (x,y)->y or (x,y)->
> (sqrt(3)/2*x+1/2*y). In the case of a circle, all the axes you would draw
> through the circle work equally well.
>
> Chuck
>
>
>
>
>
> On Wed, Jan 29, 2014 at 2:44 PM, Alexandros Drymonitis <adrcki at gmail.com>wrote:
>
>> Yeah, well I'm trying to create shapes in Gem (say a circle) and create
>> the sound they make. So, to make a circle, I'm making a ramp from 0 to 1,
>> multiply it by 2pi and send it to [cos] and [sin] and store these values in
>> two tables, which I then read for every instance of a [circle] (using
>> [repeat] and [separator]). So, since for any shape, you need two
>> coordinates, x and y, my thought was to use these two coordinates as the
>> real and imaginary part of an FFT, merging the two dimensions in one.
>> After the sinusoid, I'll try to make other shapes too, but I wanted to
>> start from that to make sure that I hear exactly what I see.
>>
>>
>> On Wed, Jan 29, 2014 at 10:30 PM, Charles Z Henry <czhenry at gmail.com>wrote:
>>
>>> What you seem to be doing is creating a spectrum which has magnitude 1
>>> everywhere, and the phase is varying at a constant rate vs frequency. That
>>> means it has a constant group delay.
>>>
>>> So... my guess is that you'd get an impulse in each block, whose timing
>>> depends on the rate of the phasor. When you vary the phasor frequency, it
>>> will coincide with the peak of the hann window at some point and be its
>>> loudest.
>>>
>>> Should be a periodic complex tone. I don't understand your goal:
>>> you've got sinusoids in the patch... to generate sinusoids?
>>>
>>> Chuck
>>>
>>>
>>> On Wed, Jan 29, 2014 at 9:12 AM, Alexandros Drymonitis <adrcki at gmail.com
>>> > wrote:
>>>
>>>> Say I have a full sine and a full cosine cycle stored in two tables.
>>>> I'm trying the following to get a sinusoid from [rifft~] but it doesn't
>>>> work.
>>>>
>>>> [phasor~]
>>>> |
>>>> [*~ sizeOfTable - 3]
>>>> |
>>>> [+~ 1]
>>>> |\
>>>> | \
>>>> | [tabread4~ sine]
>>>> | \
>>>> [tabread4~ cosine]
>>>> | \
>>>> [rifft~]
>>>> |
>>>> | [tabreceive~ hann]
>>>> | |
>>>> [*~ ]
>>>> |
>>>> [/~ 1536]
>>>>
>>>> I've set the block size to 1024 in this subpatch, and there's a hann
>>>> window in the parent patch as well. The tables have three guard points,
>>>> that's why I'm multiplying [phasor~] by the size of the table minus three
>>>> and then add one.
>>>> The output of this is a waveform with very low amplitude that kind of
>>>> bounces up and down within a sine like mask. Don't know if I'm making my
>>>> self clear. My main question is, how do you get a sinusoid out of a sine
>>>> and a cosine? Also, what's wrong in my approach?
>>>>
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>>>
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>>
>
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