Formula Device AMA

[uncle_c (kr∑th)]

Sorry to spam the formula device today, but I was thinking…

I’ve tried a number of approaches to helping other users better use the formula meta device to achieve their renoise dreams, but I haven’t really felt that helpful with any of them. It’s a totally under-utilized part of renoise, as far as I see from the anecdotal evidence of the forum.

So I’m starting this topic as a place where you can ask me anything about the formula device, and I can try to help you understand / do whatever you think you want to do with it via a more conversational approach, cuz I use it a fair amount so I’ve figured some stuff out, and I have the perception that there are things that people want to do within renoise that could actually only (or sometimes most efficiently) be achieved with the formula device. Most of the real programmers of the forum seem to put their time into tools (understandably), but my interest in cybernetics has led to be more interested in merely what control-signals can be achieved.

I’ll share a couple of super simple presets that people can look at for consideration:

playing_value_on_off.xrdp (671 Bytes)

This just allows you to set a value with input A, and then will output either that value or 0, depending on if the playhead is stopped or playing, respectively.

pattern_ramp.xrdp (675 Bytes)

This preset just outputs a “ramp waveform” that starts at 0 at the beginning of the pattern, and rises to 1 (full value) by the end.

You could use the output to control the reset of an LFO like the following device chain, so you can use different waveforms instead of an ascending ramp (note, LINE was changed to LINEF, with the former increasing per line, and the latter increasing at the same overall rate, but with tick-fraction values, so it’s “smoother”).

pattern_length_lfo.xrnt (6.0 KB)

Start including some more meta-devices before you send your “control signals” to their eventual destinations and hoo boy, you’ve got a pretty complex signal chain!

Last note for now, in case you haven’t been told:
The formula device cannot control any parameter that the hydra (for instance) cannot control, and it can only change values as fast as your project’s tick rate
(so no audio-rate fm, grainscanning, etc. Only “tick rate” modulation can be achieved on exposed parameters)

Okay hope I can be of help, lmk if there’s something you’d like to do and we can have some fun

[esaruoho]

@uncle_c

pattern_ramp.xrdp (675 Bytes)
This preset just outputs a “ramp waveform” that starts at 0 at the beginning of the pattern, and rises to 1 (full value) by the end.

hi, since you started this AMA Ask Me Anything format, I’m gonna ask you anything, and focus on this specific thing.

Ok, I see it goes from first row (0) to end of pattern (1). how would you modify this to be a counter, i.e., “reach 1 on the 512th counted row” - instead of 0…16 from 0…64 row. meaning, i’m looking for a method of, while playing a 64 row pattern, have the ramp increase until the last row of the 8th repeat of the pattern, and that’s when it’s at 1.

the objective here is to go, "here’s a repetitive pattern, that Formula reads, and then slowly ramps up from 0 to 1, without resetting, until the specific count is reached.

i used to do stuff like this with puredata easily, as i’d just have a +1 counter and once it reaches a set number, then it’d revert back to 0. but i’m not sure how to do it with formula.

so, hopefully i’m making some sense here, i.e.

[0]          [1]
[64][64][64][64]

but while consistently playing the very same pattern of same length.

[esaruoho]

here’s another.
i was doing a jam session with a friend, and realized, i need to be able to set up a system where a formula device will drop the volume from current volume to -INF, for instance, in 60 seconds or maybe 240 seconds. i.e. a really small ramp that i can trigger with the formula device itself.

is something like this possible to do? this would need to be outside of “Beats / Pattern playback” but instead locked to time. some sort of counter?
how would something like this be accomplished, please?

[unless]

The Formula is not really good for this kind of stuff because there is no “bang” input like button to start the countdown and you can’t get the current volume since you are setting it already with the Formula device. That said, you can hack something by dragging a slider up and down quickly to simulate a press and storing a start time once and checking the current time against that.

For example

local start = nil

function down_in(duration)
  if B > 0.0 then
    if start == nil then
      start = SAMPLECOUNTER
    end
  end
  
  if start == nil then return OUTPUT end
  
  if SAMPLECOUNTER > start + duration then
    start = nil
    return 0
  else
    return 1
  end
end

use

down_in(96000)

as the y output.

This will drop the volume to 0 after 2 seconds (assuming 48k sample rate) if you quickly drag B up and back to zero. You can adapt it to do a ramp instead of a hard cut and to use seconds instead of samples. Instead of trying to take the current volume, you can use another slider to set the start volume for example.

[esaruoho]

thanks for the example!
on second thought, maybe what i should actually do is just write a script that does read the current volume, and then starts counting down. i.e. something like “user preference x seconds ramp down current selected track”.
maybe it’s better. then i could just run them with a shortcut or a midibutton.
thanks for kicking the old noodle into gear.

[slujr (•X∑NøB∆B∆•••)]

Would it be possible to simulate a bang just based on a value change of one of the sliders? Then it could be a simpler mechanical input on the part of the performer

Or (most likely), perhaps I misunderstand

[unless]

Sure, just have to store the previous value of the slider and compare to that, that could be a bit better for the slider UX, just more code. The example above starts the countdown if you drag the B slider to anything higher than 0, but if the slider is still at that value after the countdown, the whole thing will restart, by doing your suggestion it could start on any change and not restart.

If the performer were to map a momentary midi cc button to the slider, both solutions would work as expected.

[esaruoho]

@slujr @unless
this seems to work, but requires me to set the volume with A-slider and then C-slider will start the countdown.

-- Persistent variables
local start=nil
local prev_C=nil
local init_vol=nil

function fade_out(duration)
  if prev_C~=C then
    prev_C=C
    start=SAMPLECOUNTER
    init_vol=A -- Capture the volume at the moment C changes
  end

  if start==nil or init_vol==nil then return A end -- No change, maintain current volume

  local elapsed=SAMPLECOUNTER-start
  if elapsed>=duration then
    start=nil
    return 0 -- Fully faded out
  else
    return init_vol*(1-elapsed/duration) -- Interpolated fade
  end
end

fade_out(240*SRATE)

it’s not quite that it works yet, but it’s at least something. unfortunately A does not set the volume so i need to match the A with the actual track volume. i guess i could save the formula device preset so that A is at “0.0dB” - so that in most cases, the situation works. i’m not sure if that’s the best possible solution tho.
edit: btw if i set the A-slider to “0.70798” - it while setting volume sets it to 0.0dB but then the slider jumps to 0.708.

so that’s not ideal.

and when it hits -INF, then it immediately jumps back to the original volume, instead of staying quiet.

[esaruoho]

ok looks like this might be the deal

-- A sets the volume for Mixer:Volume
-- B, when moved >0.0 - starts the countdown
-- fade_out(5*SRATE) = 5 seconds.
-- Modify to requirements.
-- 
-- Persistent variables
local start=nil
local prev_B=0
local init_vol=nil
local faded_out=false

function fade_out(duration)
  -- Detect if B moves from 0.0 to any nonzero value (first time only)
  if prev_B==0 and B>0 then
    prev_B=B -- Store the new value to prevent retriggers
    start=SAMPLECOUNTER
    init_vol=A -- Capture volume at fade start
    faded_out=false -- Reset fade state
  end

  -- If fade hasn't started, return current volume
  if start==nil or init_vol==nil then return A end

  -- Compute elapsed time
  local elapsed=SAMPLECOUNTER-start

  -- If fade completed, ensure volume stays at 0 and block restarts
  if elapsed>=duration then
    faded_out=true
    return 0
  end

  -- If already faded out, keep at 0
  if faded_out then return 0 end

  -- Apply linear fade
  return init_vol*(1-elapsed/duration)
end

i’m gonna see what happens when i hit it aka “load it into a track”.

okay… got it going.
made a manual and an instant version.

i think the best way to improve this would be to put the seconds as a variable in the editor, so you just hit the line and change the number.

EDIT:

[unless]

Here, made one more similar to the built-in Inertia preset.

Drag the Target slider to a value you want the target to go and it will follow it. Contrary to the Inertia preset this will do the fading at a fixed duration.

I’ve included helpers to be able to define the duration in a more readable but flexible format like beats(4), seconds(10) or lines(9) and different easings to allow for (de)accelaration around the end points.

SliderSmoothie.xrdp (4.4 KB)

[esaruoho]

thanks! yours looks very complex and very nice. and it is much better than mine for sure. but, when i load it, i get this:

weird… after i wrote it as BEATS i got a different error, then wrote it as beats and now it works.
but if i change beats → beat and then back to beats, still get the same error. i wonder what’s going on

[unless]

Thanks, it seems my Formula device works differently. I’ve updated my comment above to not error out: instead of editing the code, the duration is now written on the y = ... line to avoid the function not being in scope.