Random Pan Positions in Rapture

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dmbaer
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2009/09/17 12:53:33 (permalink)

Random Pan Positions in Rapture

I'm using Rapture (full edition) version 1.2.
 
I am attempting to use the Bipolar Random value with the Modulation Matrix to achieve a random pan position for each new note.  In theory, this should be straightforward.  I set the source to Bipolar Random, and the Destination to Pan 1 with a Depth of 100(%).  As I understand it, each Note On generates a new random number between -1 and 1 which is multiplied by the depth value (100) to get a pan position, which should be between -100% and +100%.  The typo in the documentation saying the value is generated at note off is understood.  I think we can all agree the value is generated at note on, not note off.
 
Have I got that right so far?  Because in practice, it isn't working.  I'm seeing a very left-oriented set of pan positions being generated.
 
This should be very easy to duplicate.
1. Bring up rapture with empty program
2. Set E1 wave to any saw or pulse wave (I used 016 - saw mini)
3. Set velTrack to 0.0
4. Set E1 vol and master vol so that master meter peaks at about 2/3 of max (should always be equal for both channels at this point)
5. In the Mod Matrix, set source to Random Bipolar and Destination to Pan 1 with Depth of 100
 
Start hitting middle C (or another note for that matter).  Do you see (using the master meter as your reference):
- lots of predominantly-L responses
- a fair number of more-or-less centered responses
- only rarely predominantly-R responses (if any at all)?
 
Now, if I set the E1 pan control to 100% (full clockwise), I get the random distribution I would have expected with pan control at 0% (dead center).
 
So, am I interpreting the documentation incorrectly or is Rapture behaving contrary to how the doc. says it should behave in this regard?  Thanks for any guidance on this.
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    b rock
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    Re:Random Pan Positions in Rapture 2009/09/17 18:17:02 (permalink)
    am I interpreting the documentation incorrectly or is Rapture behaving contrary to how the doc. says it should behave in this regard?
    I've been working with Rapture since it came out, and yet there are still some parameter-specific rules that I don't quite grasp.  Certainly, there are exceptions to (or conditions that affect) a strict "add/subtract" behavior that one might expect; depending on the Modulator.
     
    With panning, I suspect that some type of 'pan law' comes into play near hard left or right; much like the Width control compensates levels as you approach a mono mixdown of two stereo channels.  I also have a theory ... As (some) parameter values exceed the maximum allowable value in real-world units, the remainder 'wraps around' to keep it in a valid value range.
     
    Here's an example:  Put together a patch exactly as you have described above (Matrix 'slot' and all)
    Now add a Pan LFO with the following values:
     
    Waveform: Random Bipolar
    Status: On
    Freq: 0.00
    Sync: n/a
    Delay: n/a
    Fade: n/a
    Depth: 100%
     
    A Freq value of 0.00 will generate a random value on each note-on, based on the current Depth value.  On paper, you would think that this kind of combined routing might skew the probabilities in unexpected ways.  But it's closer to the distribution that you were looking for above; quite possibly with a higher occurrence of hard left & hard right.
     
    Any analysis of 'random' through observation is going to have a subjective quality to it.  But I do recall asking Rene point-blank on how the random values were generated.  His answer (and I'm paraphrasing) was, "As random as random can be".  Something about being based on a formula utilizing the elapsed time from an atomic clock ...
     
    Not sure that did much for answering your question.  It's more along the lines of "I'm right there beside you on this one."
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    dmbaer
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    Re:Random Pan Positions in Rapture 2009/09/18 12:28:49 (permalink)
    For what it's worth, I tried something else last night.  I put the pan control full counter-clockwise (-100%).  I got a legit random distribution when the mod. matrix depth value was -100.  Maybe I'll have a "Eureka!" moment on this, but for the moment, I just can't get my head around what's going on here.
      
    By the way, I'm perfectly willing to believe that the randomness of the generated number sequence is sufficient.  The question is: what kind of calculation is at play behind the scenes controlling this particular modulator?
      
    And, yes, like you I've observed some mod. matrix manipulations that take values beyond what their real-world limits ought to be.  Volume is one that seems to be subject to such excesses.  In fact, volume is another mystery with respect to the mapping calculation.  Let's say you map CC1 to E1 Vol.  If you set the vol. control fully counter-clockwise, you can't get any sound at all even with the mod wheel fully "up".  If you set it to a very low value like 2% (I think it's % units but I'm not at my music machine), you can make it audible.  If you set the control at 50%, you get a loudness that's way beyond what you could with no mod. matrix participation.  Or it least it seems that way.

    I'm right there beside you on this one.

    Well, ignorance loves company.  It's nice to know I'm not just being stupid.
    post edited by dmbaer - 2009/09/18 12:31:04
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