[sdiy] Silly vector synth question

[Tom Wiltshire]

I looked at the actual hardware joystick I've got hanging around and was surprised to discover this circle doesn't make as much difference as I thought it would. If I push fully over to 'A', then one of the pots is at the extreme end of its travel. If I push up to 'B', the other pot is at the extreme end of its travel. If I slide the stick around the edge of the circle between them, they do move back towards the centre a tiny bit, but only a mm or 2.
In short, the reality on this particular joystick is nothing like the virtual Wavestation situation.

And anyway, it's all a bit moot - my hardware joystick is fitted with 220degree pots, of which only the central 40degrees is used. This means you're going to have to calibrate the thing for the ends of the travel somehow, so there's lots of potential adjustments to be had.

Regards,
Tom

On 7 Feb 2011, at 23:00, Richard Wentk wrote:

> Component 1 *is* a circle on the hardware. 
> 
> I may be getting confused if people are assuming that the diamond/square are the outer limits of the movement. 
> 
> They aren't. The path around the edge of the mixer is the in-circle of the diamond, so it's not physically possible to reach 0-100% in both axes all the way around the path.
> 
> See e.g. here:
> 
> http://biopixmod.com/images/93sshot_1_153f4b8.jpg
> 
> So for example if I use Tom's equation when the pointer is at A, I *should* get 1:0:0:0. 
> 
> But in fact the joystick is offset inwards from A because it's on the edge of the circle and it can't be moved to A - so I still get a mix of the other oscillators. 
> 
> R
> 
> On 7 Feb 2011, at 05:22, Tristan wrote:
> 
>> I like this idea!
>> 
>> But if component 1 was represented as a circle rather than a square then you could have an 
>> arbitary number of different sources, uniformly or non uniformly distributed, around the circle. 
>> Moving the stick around the edge of the circle would give a crossfade between each successive pair 
>> of sources. This would be like wavetable/wave sequencing.
>> 
>> Component 2 would be the sum of each of the sources divided by total number of sources. So 
>> moving the stick closer to the centre of the circle would crossfade from the wave mix at that angle 
>> on the circle to the sum of all sources, as for vector synthesis. You could also add quirks by adding 
>> additional sources to component 2 that are not present on the circle or removing sources present 
>> on the circle. Changes in the number of sources in component 2 would require adjusting the divisor 
>> accordingly. 
>> 
>> So for one source on the circle the vector movement would have no effect. For two sources 
>> distributed at 180 degrees on the circle you would get a linear crossfade. But for 3 or more sources 
>> you would have many interesting vector synthesis possibilities.
>> 
>> /Tristan
>> 
>> On Mon, Feb 7th, 2011 at 3:26 PM, Richard Wentk <richard at wentk.com> wrote:
>> 
>>> I'd guess it works like this:
>>> 
>>> Component 1 is a simple four axis volume control, with zero in the middle.
>>> Pushing the stick N scales the N output from 0 to 1, but with no S.
>>> Pushing it S scales from 0 to 1, but with no N. E+W work similarly.
>>> 
>>> Component 1 gives you the correct mix around the edges, but creates a zone
>>> of silence towards the middle. 
>>> 
>>> Component 2 is a static 0.25*(N+S+E+W) mix of all four components that
>>> fills in the zone of silence. 
>>> 
>>> The relative mix of 1+2 is scaled by the *radius* from the centre
>>> position. So when the radius is 0, you get component 2 only, with the
>>> correct centre mix. When radius is 1, you get the edge mix from component
>>> 1. 
>>> 
>>> For all other radius values, you get a correct proportional mix of all
>>> four components.
>>> 
>>> Doing the rect to pol conversion is slightly more work, but you only need
>>> to do it for each control change. 
>>> 
>>> I'm not sure linear scaling covers this. At - say - NE, you should get
>>> 50:50:0:0. If you use linear scaling, you get some element of W+S mixed
>>> in, because the x & y distances from W+S aren't 100%.
>>> 
>>> R
>>> 
>> 
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