Disclaimer:
I'm a musician, just installed Pd a few weeks ago and quickly realised that I need to better understand the underlying math of it all.

The small idea:
I'm learning Pd by reading help files and the manual while trying to build a synth where I can change the shape of the osc~ wave via AM, FM and folding. This part is going great so far.

The big idea:
I wish I could display the wave form and how the shape changes while being modulated, folded, clipped, etc... It's useful, plus super fun!
However, I thought of a "static display" that shows only one cycle of the wave. It works "fine enough" if the frequency is 48 and the size of the array is 1000, but as soon as you change the frequency it starts showing more cycles or less, as one would expect, of course.

The questions:

• It works at these values (48hz and size 1000) because my sample rate is 48k. Is this correct?
• Is there a way to do what I want? If so, what would you advise me to study?

Note:
I've got the inspiration to do so after using Glänta, a M4L device by Fors. I don't know how they do it, but the visual aspect of their  devices is usually customised with JS stuff. I don't believe that is a "true" wave, but an animated representation of it. But again, don't quote me on that, it's just a hunch (;

Files:

• a Pd patch with an example of the display idea mentioned above
• a txt file with the array values as list. You can see that is not perfect, but close enough (;

capturingOneCycle.pd array1_list_values.txt

@blindingSlow I think you're right about why 48 Hz works.

A lot of oscillators use [phasor~] to compute each cycle, so you could use that to write your display. I found a way to do it using Gem years ago and never looked for another way, but I think nowadays there are other oscilloscope abstractions available. Here is a variable duty-cycle triangle wave thing. Click on [create, 1( first to open the Gem display window.
one cycle display.pd

PS is it still called "duty-cycle" if it's not a square wave? I'm not a synthesist.

@blindingSlow You can use [resize( method for array or [array size] and a little math to change the array's size to what it needs to be for a given frequency. To make it work with any samplerate you can use [samplerate~] to get the samplerate which pd is currently ruining at.

@jameslo wow, your idea is so much better than mine hehehe

I'm still learning the basics of Pd and signal processing, so I haven't installed Gem or other externals yet, just using the pure vanilla until I understand it.
I downloaded your patch and bookmarked this thread for easy future reference.
Thank you very much!

@jameslo said:

PS is it still called "duty-cycle" if it's not a square wave? I'm not a synthesist.

In the synthesis world that would generally be called variable slope. I don't think this would be variable duty cycle from the electronics standpoint either since duty cycle refers to the on vs off time and that remains constant in this use. A variable duty cycle triangle would essentially just be a [clip~ x 1].

@oid That is good to know. I will try it later today.
Do you know if I can use a variable for the array size message? Something like: array size $1
I'm running faster than I can read the manual, so there is a lot of gaps inside my brain right now (;
Thanks!

@blindingSlow
Give a read through the help files for messages and graphical arrays.

@oid said:

Give a read through the help files for messages and graphical arrays.

I shall... it's a lot of details to read, test and understand, but I'll get there soon enough (;
THanks

@blindingSlow There is a fair amount of information there but it is mostly just variations on the same methodology so once you get the basics down it comes quickly. Regarding drawing waves, sometimes it can be better to use a fixed frequency oscillator for the display and just duplicate everything for the part you are listening too. Everytime you resize an array you are reallocating the array which is not the fastest process and if you turn the frequency of your wave low down to 0.1 hz you have to wait 10 seconds for it to update the display. With a fixed frequency you avoid reallocating memory and keep the display responsive but you are asking more of from the UI with all those updates and if you are doing a good deal of manipulation to the waveform duplicating everything could be more expensive than the reallocations. Need to find the balance between trade offs for the given situation.

display.pd

Also, just remembered you had some eyesight issues, was my screenshot readable for you? If I am just uploading a screenshot of something basic which does not require the patch to demonstrate should I do the screenshot zoomed in or always upload the patch?

Edit: If you were going to make a display like this to use in a patch and not just learning you would want to stick it in a subpatch so you can use [switch~] to turn the duplicated objects off when the display in not being updated.

@jameslo one-cycle-display_gem.pd this needs declare lib gem